British Airways Suspends Flights To Two Ebola Stricken Nations

Credit CDC Ebola Website

 

# 8917

 

In addition to the immense public health ramifications, the Ebola outbreak in Western Africa also carries with it serious economic, and logistical impacts as well. 

 

Today, British Airlines announced the suspension of all flights to and from Liberia and Sierra Leone are canceled for the remainder of August.

 

This announcement was posted a short time ago on the BA website.

 

Flights to/from Liberia and Sierra Leone suspended

Answer Id 5072   |    Updated 05/08/2014 05.08 PM (UK time)

Summary

British Airways has temporarily suspended flights to and from Liberia and Sierra Leone until 31 August 2014 due to the deteriorating public health situation in both countries.

More information

The safety of our customers, crew and ground teams is always our top priority and we will keep the routes under constant review in the coming weeks.

What to do if your flight has been cancelled

If your flight has been cancelled, please do not travel to the airport.

We have a policy in place outlining the options available to you and how to make changes to your booking.

> Re-booking options if your flight has been cancelled

In addition we have made the following options available to you up to the 31 August 2014:

A rebooking to a later date on a British Airways flight to/from Liberia or Sierra Leone from 1 September 2014.

A rebooking with British Airways on its flights in August between London and Abuja, Lagos, Accra or Nairobi. The journey between Liberia or Sierra Leone to/from these four African cities will be at the customer's own expense.

We are also speaking with other carriers to discuss other options which may be available for customers.

(Continue. . . )

 

CDC Interim Ebola Exposure Guidance For Airlines, Flight Crews

Range of Reported Ebola Outbreaks 1976-2014 – Credit WHO

 

 

 

# 8870

 

The story – confirmed this morning in the latest WHO update (see WHO Ebola Update – July 25th) – that a `probable’ Ebola patient (who died in isolation yesterday) traveled by airplane from Liberia to Lagos, Nigeria last Sunday `while symptomatic’  has captured headlines overnight.

Although the WHO statement did not elaborate on his symptoms, according to multiple media accounts (see here, and here) the patient became ill on the flight and vomited, and was quarantined upon landing.

 

Although I’ve not seen any description of the type of aircraft or number of passengers, according to a BBC report today (see Nigeria 'placed on red alert' over Ebola death), Health Minister Onyebuchi Chukwu is quoted as saying `. . . the other passengers on board the flight had been traced and were being monitored’ .

 

You may recall that a little over a month ago, we saw Spain Testing Traveler For Possible Ebola Infection, but in that case the patient tested negative.

 

At the time, we looked at the ECDC’s  Rapid Risk Assessment on Ebola (June 9th), where experts worked out several scenarios where the Ebola virus might travel to the European Union, and their recommended response to Scenario 3: Passenger with symptoms compatible with EVD on board an airplane.

Similarly the CDC has also published their own guidance on how to deal with a probable or suspected Ebola case on an airplane.

 

Interim Guidance about Ebola Virus Infection for Airline Flight Crews, Cleaning and Cargo Personnel

Overview of Ebola Disease

Ebola hemorrhagic fever is a severe, often-fatal disease caused by infection with a species of Ebolavirus. Although the disease is rare, it can spread from person to person, especially among health care staff and other people who have close contact* with an infected person. Ebola is spread through direct contact with blood or body fluids (such as saliva or urine) of an infected person or animal or through contact with objects that have been contaminated with the blood or other body fluids of an infected person.

The likelihood of contracting Ebola is extremely low unless a person has direct contact with the body fluids of a person or animal that is infected and showing symptoms. A fever in a person who has traveled to or lived in an area where Ebola is present is likely to be caused by a more common infectious disease, but the person would need to be evaluated by a health care provider to be sure.

The incubation period for Ebola ranges from 2 to 21 days. Early symptoms include sudden fever, chills, and muscle aches. Around the fifth day, a skin rash can occur. Nausea, vomiting, chest pain, sore throat, abdominal pain, and diarrhea may follow. Symptoms become increasingly severe and may include jaundice (yellow skin), severe weight loss, mental confusion, shock, and multi-organ failure.

The prevention of Ebola virus infection includes measures to avoid contact with blood and body fluids of infected individuals and with objects contaminated with these fluids (e.g., syringes).

Management of ill people on aircraft if Ebola virus is suspected

Crew members on a flight with a passenger or other crew member who is ill with a fever, jaundice, or bleeding and who is traveling from or has recently been in a risk area should follow these precautions:

• Keep the sick person separated from others as much as possible.
• Provide the sick person with a surgical mask (if the passenger can tolerate wearing one) to reduce the number of droplets expelled into the air by talking, sneezing, or coughing.
• Tissues can be given to those who cannot tolerate a mask.
• Personnel should wear impermeable disposable gloves for direct contact with blood or other body fluids.
• The captain of an airliner bound for the United States is required by law to report to the Centers for Disease Control and Prevention (CDC) any ill passengers who meet specified criteria. The ill passenger should be reported before arrival or as soon as the illness is noted. CDC staff can be consulted to assist in evaluating an ill traveler, provide recommendations, and answer questions about reporting requirements; however, reporting to CDC does not replace usual company procedures for in-flight medical consultation or obtaining medical assistance.

General Infection Control Precautions

Personnel should always follow basic infection control precautions to protect against any type of infectious disease.

What to do if you think you have been exposed

Any person who thinks he or she has been exposed to Ebola virus either through travel, assisting an ill passenger, handling a contaminated object, or cleaning a contaminated aircraft should take the following precautions:

• Notify your employer immediately.
• Monitor your health for 21 days. Watch for fever (temperature of 101°F/38.3°C or higher), chills, muscle aches, rash, and other symptoms consistent with Ebola.

When to see a health care provider

• If you develop sudden fever, chills, muscle aches, rash, or other symptoms consistent with Ebola, you should seek immediate medical attention.
  • Before visiting a health care provider, alert the clinic or emergency room in advance about your possible exposure to Ebola virus so that arrangements can be made to prevent spreading it to others.
  • When traveling to a health care provider, limit contact with other people. Avoid all other travel.
• If you are located abroad, contact your employer for help with locating a health care provider. The U.S. embassy or consulate in the country where you are located can also provide names and addresses of local physicians.

(Continue . . . )

 

 

As you can see, the CDC (and ECDC) response to these sorts of exposures is far less draconian than movies and TV might lead one to assume.  Awareness and self monitoring for symptoms, not automatic quarantine, is the norm.

 

Although considered a low probability event, with millions of airline passengers every year, and an incubation period up to three weeks - it isn’t inconceivable for Ebola (or other viral hemorrhagic fever)  to board an airplane undetected.

 

After all, over the past decade we’ve seen three cases of Lassa fever imported in the United States (see Minnesota: Rare Imported Case Of Lassa Fever).

The bottom line  is that we ignore global healthcare and infectious disease outbreaks – even in the remotest areas of the world – at our own peril. Vast oceans and extended travel times no longer offer us protection. There are no technological shields that we can erect that would keep viruses like Ebola, MERS-CoV, or pandemic influenza from finding their way to our shores.

 

Which makes the funding and support of international public health initiatives, animal health initiatives, and disease surveillance ever so important, no matter where on this globe you happen to live.

Shakes On A Plane

 

Credit Wikipedia

 

 

# 8614

 

The news yesterday that a second MERS infected Health Care Worker (HCW) flew into the United States from Saudi Arabia is additional proof (as if we needed it) that airlines are a competent vector of infectious diseases, and that oceans and borders offer little protection against the proliferation of emerging viruses.

 

The early (prodromal) presentation of MERS can be mild and non-specific enough (typically fever, chills, malaise) to convince most patients – even HCWs who have recently worked in a MERS hot zone – that what they have is nothing more than a `summer cold’. 

Add in the fact that these early symptoms don’t present until days after exposure – well, short of placing Samuel L. Jackson on every international flight - there’s not much hope (warning: gratuitous movie reference ahead) in eliminating Shakes on a Plane.  

 

Granted, one would hope that in this age of emerging infectious disease, anyone feeling unwell on an airline flight would request - and be provided with - a surgical facemask.  HCWs, particularly those coming from an area where MERS is active, should certainly give extra consideration to the fact that they might be infected.

Hopefully some appropriate signage at airports informing passengers of the symptoms of MERS, and that they should notify the flight crew if they feel unwell, will lead to these sorts of measures.

 

But the reality is, denialism – combined with an overwhelming desire to `get home’ – may induce some people to wait to see if they feel worse before saying anything that might endanger their itinerary.  During the initial outbreak of H1N1, we saw airline passengers taking fever-reducers to beat the airport scanners in order to get home (see Vietnam Discovers Passengers Beating Thermal Scanners).

 

During yesterday’s CDC press conference, CDC Director Tom Frieden addressed the topic of airport screening for possible MERS cases:

 

In terms of the border issues, CDC has quarantine stations at all of the major airports of entry in the U.S.  If someone has symptoms, we are immediately contacted.  If need be, we will go on board the plane.  We do not recommend screening of people coming off. We don't find that to be productive.  First off, many people who may be ill may not be identified as being ill.  And second, many people who will be ill with routine colds and minor conditions would be.  So we've looked at that and not found that to be something we would recommend at this time.

 

A bit of a misnomer, `quarantine stations’  aren’t actually quarantine facilities, but are stations - located at 20 ports of entry and land-border crossings (see map below) - that are staffed by CDC medical and public health officers.

 

Location of US CDC Quarantine Stations

 

The CDC Quarantine Station  FAQ lists their Mandate:

 

Authority and Scope

CDC has the legal authority to detain any person who may have an infectious disease that is specified by Executive Order to be quarantinable. If necessary, CDC can deny ill persons with these diseases entry to the United States. CDC also can have them admitted to a hospital or confined to a home for a certain amount of time to prevent the spread of disease.

Daily Activities

Medical and public health officers at U.S. Quarantine Stations perform these activities:

Response

• Respond to reports of illnesses on airplanes, maritime vessels, and at land-border crossings
• Distribute immunobiologics and investigational drugs
• Plan and prepare for emergency response

Quarantinable Diseases by Executive Order

• Cholera
• Diphtheria
• Infectious tuberculosis
• Plague
• Smallpox
• Yellow fever
• Viral hemorrhagic fevers
• SARS
• New types of flu (influenza) that could cause a pandemic

Migration

• Monitor health and collect any medical information of new immigrants, refugees, asylees, and parolees
• Alert local health departments in the areas where refugees and immigrants resettle about any health issues that need follow up
• Provide travelers with essential health information
• Respond to mass migration emergencies

Inspection

• Inspect animals, animal products, and human remains that pose a potential threat to human health
• Screen cargo and hand-carried items for potential vectors of human infectious diseases

Partnerships

• Build partnerships for disease surveillance and control

 

Although it isn’t what most people want to hear, there is no technological barrier that can effectively keep infected people from traveling internationally.  It is the price we pay for having an increasingly mobile, and interconnected, society.

 

Last month, in MERS: The Limitations Of Airport Screening, we looked at the poor performance of airport screening programs during the H1N1 pandemic, and the scientific consensus that screening programs are unlikely to provide much benefit (see Helen Branswell’s Airport disease screening rarely worthwhile, study suggests).

 

 

The good news – at least as far as we know today – is that MERS shows no signs of being anywhere near as contagious as influenza, and that the risks of contracting it through casual contact with an infected person is thought exceedingly low.  Family members, care givers, those with close, prolonged contact, and HCWs appear to be most at risk.

 

Meaning that simply sharing the same air flight, or standing in queue at the air terminal with someone who is infected, is unlikely to present much risk.

The concern is, that over time MERS may gain transmissibility, making it a greater public health threat.   If that will happen is unknowable, but each human infection gives the virus another opportunity to `figure us out’.

 

But whether the next pandemic threat turns out to be due to MERS, one of the many strains of avian or swine flu (or something completely out of left field), our best defense is for emerging viruses be identified and quashed at the source, before they have the opportunity to board a plane and spread globally.

 

Making investments in global health, research, and human (and animal) surveillance relatively cheap insurance for a world that is increasingly vulnerable to another great pandemic.

 

 

Apparently I’m not the only one with MERS and Travel on the brain this morning, as Dr. Ian Mackay has his own offering called:

 

MERS-CoV on a plane!

"Assessment of the MERS-CoV epidemic situation in the Middle East region."
Reprinted with kind permission of author (Dr Vittoria Colizza, pers comm).Click on image to enlarge.

 

This is perhaps a timely reminder of where cases of MERS-CoV may pop-up if we look at the author's analysis of destinations from major departure airports in the Kingdom of Saudi Arabia, Jordan, Qatar and the United Arab Emirates.

(Continue . . . )

Science: The Hidden Geometry of Complex, Network-Driven Contagion Phenomena

Scheduled airline traffic around the world, circa June 2009 – Credit Wikipedia

# 8067

 

Purely by chance, just weeks before the 2009 H1N1 virus broke out of Mexico and began to wing itself around the globe via international air traffic, I penned a blog called How The Next Pandemic Will Arrive. That blog was inspired by a video (below) made by ZHAW (Zürcher Hochschule für Angewandte Wissenschaften)  showing 24 hours of air traffic around the world compressed into just over a minute.

 

Since then, we’ve looked at the role of air traffic in the spread of infectious disease a number of times, including a PLoS One  study from MIT: Contagion Dynamics Of International Air Travel that simulated the early spread of a pandemic virus via air travel and ranked U.S. airports based on how much they contributed to the spread of the illness, and a number of studies suggesting that airport screening for infected travelers would likely be ineffective.

 

Branswell: Limitations Of Airport Disease Screening

Japan: Quarantine At Ports Ineffective Against Pandemic Flu

Fluing The Friendly Skies

 

Today, in the Journal Science, we get a new look at the simulated spread of a SARS or H1N1-like virus via international air travel from authors  Dirk Brockmann and Dirk Helbing with the innocuous sounding title of:

 

The Hidden Geometry of Complex, Network-Driven Contagion Phenomena

Dirk Brockmann , Dirk Helbing

Science 13 December 2013:
Vol. 342 no. 6164 pp. 1337-1342
DOI: 10.1126/science.1245200

 

 

While the bulk of this study is behind a pay wall, we get a preview of its findings (and a fascinating video) from a press release via Berlin’s Humboldt-Universität.

(Click Image to view video)

 

The Hidden Geometry of Global Contagion

New mathematical theory for the global spread of epidemics

Scientists at Berlin’s Humboldt-Universität, ETH Zurich, Northwestern University and Robert Koch Institute develop a new mathematical theory for the global spread of epidemics. Insights cannot only facilitate finding an outbreak’s origin, but may significantly improve the forecast of global spreading pathways. The results of the study “The hidden geometry of complex, network-driven contagion phenomena” have recently been published in the journal Science.

When an unknown virus emerges at various locations in the world, scientists focus on answering the following questions: Where did the new disease originate? Where are new cases to be expected? When are they expected? And how many people will catch the disease? In order to contain the further spread – and potentially devastating consequences – rapid assessment is essential for the development of efficient mitigation strategies. Highly sophisticated computer simulations are an important tool for forecasting different scenarios: These simulations attempt to predict the likely epidemic time-course and spreading pattern. However, the computer simulations are very demanding in terms of computer time. They also require knowledge of disease-specific parameters that are typically not known for new, emergent infectious diseases.

Theoretical physicist Dirk Brockmann, Professor at Berlin’s Humboldt-Universität, and his fellow scientist Dirk Helbing, Professor at ETH Zurich, now propose a different approach for understanding global disease dynamics:  “Our theory is based on the intuitive notion that in our strongly connected world, conventional geographic distances are no longer the key variable but must be replaced with effective distances,” they explain. “From the perspective of Frankfurt, Germany, other metropolitan areas such as London, New York or Tokyo are effectively not more distant than geographically close German cities such as Bremen, Leipzig or Kiel,” says Brockmann, who developed the ideas for this research at the Northwestern Institute on Complex Systems. In their work, the researchers show that effective distances can be computed from the traffic intensities in the worldwide air-transportation network: “If the flux of passengers from A to B is large, the effective distance is small and vice versa. The only thing we had to do was to find the right mathematical formula for this,” Helbing explains.

(Continue . . . )

 

While I’ve said it before, it’s worth repeating:

 

The takeaway from all of this is that we ignore global healthcare and infectious disease outbreaks – even in the remotest areas of the world – at our own peril. Vast oceans and extended travel times no longer offer us protection, and there is no technological shield that we can erect that would keep an emerging pandemic virus out.

 

The place to try to stop the next pandemic is not at the airport gate, but in the places around the world where they are likely to emerge.

 

Which makes the funding and support of international public health initiatives, animal health initiatives, and disease surveillance ever so important, no matter where on this globe you happen to live.

Pathogens At the Gate

Thermal Scanner – Credit Wikipedia

 

# 6593

 

While there are no indications that the coronavirus detected recently in the Middle East has spread beyond the first two cases, some places around the world are taking this threat very seriously.

 

For example, local media is reporting that thermal scanners have been deployed at the Ninoy Aquino International Airport in the Philippines in an attempt to screen arrivals from the Middle East for possible infection.

 

Whenever a novel virus appears, people’s thoughts understandably turn to a pandemic scenario, even though experience has shown that most emerging viruses don’t have the `legs’ to spark a global epidemic (see Novel Viruses & Chekhov’s Gun).

 

Nevertheless, history tells us that pandemics come along several times each century, and another pandemic is all but inevitable.

 

And so the world’s attention this week has quite naturally focused on the novel coronavirus that killed one man in Saudi Arabia last July and has a Qatari man currently hospitalized in London.

 

Memories of the SARS outbreak in 2002 and 2003 remain vivid, particularly in Asia, where the virus hit hardest.

 

Fortunately, while there is still much we don’t know about this emerging pathogen, there are no immediate signs that this virus poses a pandemic threat.

 

While we may not know when - or which virus - will spark the next global health crisis, we have pretty good idea how it will arrive in most countries.

 

Scheduled airline traffic around the world, circa June 2009 – Credit Wikipedia

 

The world’s airlines carry 2.6 billion passengers each year, on more than 17 million flights.  And as the map above indicates, millions of them are international flights.

 

With most viral diseases having an incubation period of several days or longer, someone who is newly infected with a virus could change planes and continents several times before showing their first signs of illness.

 

Last July, in MIT: Contagion Dynamics Of International Air Travel we looked at a study appearing in PloS One, that simulated the early spread of a pandemic virus via air travel and ranked U.S. airports based on how much they contributed to the spread of the illness.

 

An excerpt from a report that appeared in MIT News.

 

New model of disease contagion ranks U.S. airports in terms of their spreading influence

Airports in New York, Los Angeles and Honolulu are judged likeliest to play a significant role in the growth of a pandemic.

Kennedy Airport is ranked first by the model, followed by airports in Los Angeles, Honolulu, San Francisco, Newark, Chicago (O'Hare) and Washington (Dulles). Atlanta's Hartsfield-Jackson International Airport, which is first in number of flights, ranks eighth in contagion influence. Boston's Logan International Airport ranks 15th.

 

 

All of which begs the question, can we really screen, identify, and isolate infectious airline passengers before they can spread a pandemic virus?

 

 

Sadly, the evidence to date has not been very encouraging.

 

Last April, in EID Journal: Airport Screening For Pandemic Flu In New Zealand, we examined a study that found the screening methods used at New Zealand’s airport were inadequate to slow the entry of the 2009 pandemic flu into their country, detecting less than 6% of those infected.

 

New Zealand did not employ thermal scanners, although countries that did, didn’t fare much better.

  

Proving that `there’s no place like home’ during a global crisis, in Vietnam Discovers Passengers Beating Thermal Scanners, we saw evidence of passengers taking fever-reducers to beat the airport scanners in a desperate attempt to get home.

 

In December of 2009, in Travel-Associated H1N1 Influenza in Singapore, I blogged on a NEJM Journal Watch article on of a new study that has been published, ahead of print, in the CDC’s  EID Journal  entitled:

 

Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore. Emerg Infect Dis 2010 Jan; [e-pub ahead of print]. Mukherjee P et al

Travel-Associated H1N1 Influenza in Singapore

Airport thermal scanners detected only 12% of travel-associated flu cases; many travelers boarded flights despite symptoms.

 

 

In June of 2010  CIDRAP carried this piece on a study of thermal scanners in New Zealand in 2008 (before the pandemic) presented at 2010’s ICEID.

 

Thermal scanners are poor flu predictors

Thermal scanners for screening travelers do moderately well at detecting fever, but do a poor job at flagging influenza, according to researchers from New Zealand who presented their findings today at the International Conference on Emerging Infectious Diseases (ICEID) in Atlanta.

 

And in early 2009, Helen Branswell penned an article for the Canadian Press, that stated:

 

Studies show little merit in airport temperature screening for disease

Monday, 16 February 2009 - 11:58am.

By Helen Branswell

TORONTO — Using temperature scanners in airports to try to identify and block entry of sick travellers during a disease outbreak is unlikely to achieve the desired goal, a report by French public health officials suggests.

(Continue. . .)

 

 

The evidence is pretty clear.

 

With the technology of today, coupled with likelihood of having many pre-symptomatic and asymptomatic carriers, there isn’t much hope to identify more than a fraction of infected travelers.

 

As far as the risk of catching a pandemic flu virus while a passenger on an airliner, in May of 2010 we saw a study that appeared in the BMJ that looked at that very topic (see BMJ: Flu Transmission Risks On Airplanes)

 

BMJ 2010;340:c2424

Research

Transmission of pandemic A/H1N1 2009 influenza on passenger aircraft: retrospective cohort study

Conclusions

A low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

 

Another study, conducted by researchers at UCLA and published in BMC Medicine in late 2009:

 

Calculating the potential for within-flight transmission of influenza A (H1N1)

Bradley G Wagner, Brian J Coburn and Sally Blower^*

Results

The risk of catching H1N1 will essentially be confined to passengers travelling in the same cabin as the source case. Not surprisingly, we find that the longer the flight the greater the number of infections that can be expected. We calculate that H1N1, even during long flights, poses a low to moderate within-flight transmission risk if the source case travels First Class.

(Continue . . .)

 

 

While there will likely be intense public clamor to try to block the entry of a pandemic virus into this, or any other country, the truth is – it is highly unlikely that it will work.

Areas that receive a very small number of arrivals might be able to institute a quarantine system (see Can Island Nations Effectively Quarantine Against Pandemic Flu? ), but even then the ability to identify and isolate infected travelers won’t be 100%.

 

Still, even if the success rate is likely to be low, there may be some value in trying to limit the number of infected persons arriving into a country, particularly during the opening days and weeks of an outbreak.

 

The more introductions of a virus into a population, the more points it will have from which to spread.

 

Since it takes months to produce and deploy a vaccine, and time to prepare a society to deal with a pandemic, any delaying action that can reduce the speed and spread of the virus has value.

 

The takeaway from all of this is that we ignore global healthcare and infectious disease outbreaks – even in the remotest areas of the world – at our own peril.

 

Vast oceans and extended travel times no longer offer us protection, and there is no technological shield that we can erect that would keep an emerging pandemic virus out.

 

The place to try to stop the next pandemic is not at the gate, but in the places around the world where they are likely to emerge.

 

Which makes the funding and support of international public health initiatives, animal health initiatives, and disease surveillance ever so important, no matter where on this globe you happen to live.

MIT: Contagion Dynamics Of International Air Travel

 

 

 

# 6446

 

In 2009, about 6 weeks before news of the outbreak of H1N1 in Mexico was announced, I came across a fascinating video on Youtube which inspired a blog called How The Next Pandemic Will Arrive.

 

I wrote:

 

There is a lot we don't currently know about the next pandemic.  We don't know when it will arrive.  We don't know what virus will cause it.  And we don't know how bad it will be.

 

But there is one thing almost certain.

 

It will arrive in most countries by airplane.

 

 

 

Not exactly an earth shattering revelation, given that air travel is an obvious mode of viral spread. But my timing was excellent.

 

By the end of following month the new H1N1 virus was winging its way around the globe in large part due to spring break vacationers returning from Mexico.

 

While obviously a major factor, the dynamics of disease spread through airports is only partially understood.  

 

We’ve a new study, appearing in PloS One, that looks at the early spread of a pandemic virus through air travel, and through the use of Monte Carlo simulations, finds some airports contributing more to the spread of a pandemic than the number of travelers passing through it might suggest.

 

The study, conducted by researchers at MIT, is called:

 

A Metric of Influential Spreading during Contagion Dynamics through the Air Transportation Network

Christos Nicolaides, Luis Cueto-Felgueroso, Marta C. González, Ruben Juanes

Abstract

The spread of infectious diseases at the global scale is mediated by long-range human travel. Our ability to predict the impact of an outbreak on human health requires understanding the spatiotemporal signature of early-time spreading from a specific location.

 

Here, we show that network topology, geography, traffic structure and individual mobility patterns are all essential for accurate predictions of disease spreading. Specifically, we study contagion dynamics through the air transportation network by means of a stochastic agent-tracking model that accounts for the spatial distribution of airports, detailed air traffic and the correlated nature of mobility patterns and waiting-time distributions of individual agents.

 

From the simulation results and the empirical air-travel data, we formulate a metric of influential spreading––the geographic spreading centrality––which accounts for spatial organization and the hierarchical structure of the network traffic, and provides an accurate measure of the early-time spreading power of individual nodes.

 

I would invite those with a better grasp of statistical analysis than I to read the entire study, but for the rest of us, we have the following report from MIT News.

 

Monday, July 23

New model of disease contagion ranks U.S. airports in terms of their spreading influence

Airports in New York, Los Angeles and Honolulu are judged likeliest to play a significant role in the growth of a pandemic.

Denise Brehm, Civil and Environmental Engineering

World map shows flight routes from the 40 largest U.S. airports.

Image: Christos Nicolaides, Juanes Research Group

Public health crises of the past decade — such as the 2003 SARS outbreak, which spread to 37 countries and caused about 1,000 deaths, and the 2009 H1N1 flu pandemic that killed about 300,000 people worldwide — have heightened awareness that new viruses or bacteria could spread quickly across the globe, aided by air travel.

<SNIP>

 

Outsize role for Honolulu

For example, a simplified model using random diffusion might say that half the travelers at the Honolulu airport will go to San Francisco and half to Anchorage, Alaska, taking the disease and spreading it to travelers at those airports, who would randomly travel and continue the contagion.

 

In fact, while the Honolulu airport gets only 30 percent as much air traffic as New York's Kennedy International Airport, the new model predicts that it is nearly as influential in terms of contagion, because of where it fits in the air transportation network: Its location in the Pacific Ocean and its many connections to distant, large and well-connected hubs gives it a ranking of third in terms of contagion-spreading influence.

 

Kennedy Airport is ranked first by the model, followed by airports in Los Angeles, Honolulu, San Francisco, Newark, Chicago (O'Hare) and Washington (Dulles). Atlanta's Hartsfield-Jackson International Airport, which is first in number of flights, ranks eighth in contagion influence. Boston's Logan International Airport ranks 15th.

(Continue . . . )

 

 

Complicating matters - attempts to identify and quarantine air travelers with fevers, or other signs of illness - have proved notoriously difficult.

 

Last April, in EID Journal: Airport Screening For Pandemic Flu In New Zealand, we looked at a study that found that the screening methods used at New Zealand’s airport were inadequate to slow the entry of the 2009 pandemic flu into their country, detecting less than 6% of those infected.

 

Unlike some other countries in 2009, New Zealand did not employ thermal scanners, which look for arriving passengers or crew with elevated temperatures. 

(Thermal Imaging for SARS in 2003)

 

But even countries that employed thermal scanners and far more strict interdiction techniques during the summer of 2009 failed to keep the flu out.

 

Just as the pandemic was ramping up, in Vietnam Discovers Passengers Beating Thermal Scanners, we saw evidence of flyers taking fever-reducers to beat the airport scanners in order to get home.

 

In December of 2009, in Travel-Associated H1N1 Influenza in Singapore, I wrote about a NEJM Journal Watch of a new study that has been published, ahead of print, in the CDC’s  EID Journal  entitled:

 

Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore. Emerg Infect Dis 2010 Jan; [e-pub ahead of print]. Mukherjee P et al

Travel-Associated H1N1 Influenza in Singapore

Airport thermal scanners detected only 12% of travel-associated flu cases; many travelers boarded flights despite symptoms.

And finally, in June of 2010  CIDRAP carried this piece on a study of thermal scanners in New Zealand in 2008 (before the pandemic) presented at 2010’s ICEID.

 

Thermal scanners are poor flu predictors

Thermal scanners for screening travelers do moderately well at detecting fever, but do a poor job at flagging influenza, according to researchers from New Zealand who presented their findings today at the International Conference on Emerging Infectious Diseases (ICEID) in Atlanta.

 

 

As far as the transmission of the influenza virus aboard an airliner, in May of 2010 we saw a study in the BMJ that looked at that very topic (see BMJ: Flu Transmission Risks On Airplanes)

 

BMJ 2010;340:c2424

Research

Transmission of pandemic A/H1N1 2009 influenza on passenger aircraft: retrospective cohort study

 

Conclusions

 

A low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

 

Another study, conducted by researchers at UCLA and published in BMC Medicine in late 2009:

 

Calculating the potential for within-flight transmission of influenza A (H1N1)

Bradley G Wagner, Brian J Coburn and Sally Blower^*

Results

The risk of catching H1N1 will essentially be confined to passengers travelling in the same cabin as the source case. Not surprisingly, we find that the longer the flight the greater the number of infections that can be expected. We calculate that H1N1, even during long flights, poses a low to moderate within-flight transmission risk if the source case travels First Class.

 

(Continue . . .)

 

While it may prove impossible to halt the spread of a pandemic via airline passengers, knowing which airports are the most likely to contribute to the spread of a new virus could aid in attempts to slow its progress.

 

Which makes research like what we’ve seen out of MIT today of more than just academic interest.

A Flu Flew Review

 

UPDATED 1800hrs EST: The latest news reports out of NZ indicate that unaffected passengers have been allowed off the plane are now going through customs.  As expected, authorities now believe the sick passengers probably contracted seasonal H3N2 influenza while in Japan.

 

 

# 6137

 

 

While we wait for an update (see update) on the Boeing 777 currently quarantined on the tarmac at Auckland airport with scores of passengers complaining of flu-like symptoms (see New Zealand : Airline Passengers Quarantined) this would seem an opportune time to look back at some of what we’ve learned about airplanes, airports, and influenza over the years.

What follows are excerpts from previous blogs, you can follow the links to read them in their entirety.

 

As I mentioned in my last blog, New Zealand has a very aggressive influenza pandemic plan, and I wrote about their drills and preparations back in October of 2008.

New Zealand: Testing Pandemic Quarantine Plans

 

New Zealand, being an island nation, is one of the few countries that believe they have at least the possibility of blocking a pandemic virus from entering their borders.

 

It is an ambitious goal.

 

And the odds of carrying it out successfully are pretty long.

 

How far they will go to try to block a pandemic virus from entering their country hasn't been decided yet by their Ministry of Health (MOH).

 

In their FAQ on pandemic influenza, the question is answered this way:

Will New Zealand stop travellers from coming into the country in an effort to stop the spread of disease?

Because we are an island nation, active management of the border (i.e. limiting arrivals from affected areas to allow us to impose effective on-arrival measures) needs to be considered among the range of options as we plan our response. Other countries are also considering border management options.

 

Any final decision on border management will be made by the Government with input from a range of government departments.

 

The details of how New Zealand might manage its borders are laid out in the National Health Emergency Plan: New Zealand Influenza Pandemic Action Plan 2006.

 

But whether the goal is to try to stop the virus from entering the country, or to simply slow the introduction while a vaccine is being produced, it takes planning and training. 

The enormity of the job of interdicting infected passengers was the subject of a blog I wrote just one month before the outbreak of the 2009 H1N1 pandemic virus.

 How The Next Pandemic Will Arrive

# 2876

There is a lot we don't currently know about the next pandemic.  We don't know when it will arrive.  We don't know what virus will cause it.  And we don't know how bad it will be.

 

But there is one thing almost certain.

 

It will arrive in most countries by airplane.

The video above, which as been making the rounds for several months, was made by ZHAW (Zürcher Hochschule für Angewandte Wissenschaften) or The Zurich University of Applied Sciences.

 

It is a simulation (using real data) showing 24 hours of air traffic around the world.  Notice how the level of activity follows the daylight.

 

Every year there are more than 17,000,000 commercial airline flights (data from year 2000 - it's probably higher now) that carry hundreds of millions of passengers each year. 

 

 

As far as the transmission of the influenza virus aboard an airliner, in May of 2010 we saw a study in the BMJ that looked at that very topic. And as the fates would have it, this study was done on a plane flight into the same airport in Auckland, New Zealand.

Note: Given the incubation period of most respiratory viruses, those who are symptomatic on today’s flight almost certainly were exposed and infected prior to boarding the flight.

 

 

Friday, May 21, 2010

BMJ: Flu Transmission Risks On Airplanes

# 4586

BMJ 2010;340:c2424

Research

Transmission of pandemic A/H1N1 2009 influenza on passenger aircraft: retrospective cohort study

Michael G Baker, associate professor¹, Craig N Thornley, medical officer of health², Clair Mills, senior lecturer³, Sally Roberts, microbiologist⁴, Shanika Perera, medical officer of health², Julia Peters, medical officer of health², Anne Kelso, director⁵, Ian Barr, deputy director⁵, Nick Wilson, associate professor¹

 

I’ve reproduced portions of the abstract below.  The entire study is available online at the BMJ.

 

Objectives To assess the risk of transmission of pandemic A/H1N1 2009 influenza (pandemic A/H1N1) from an infected high school group to other passengers on an airline flight and the effectiveness of screening and follow-up of exposed passengers.

<SNIP>

Setting Auckland, New Zealand, with national and international follow-up of passengers.

Participants Passengers seated in the rear section of a Boeing 747-400 long haul flight that arrived on 25 April 2009, including a group of 24 students and teachers and 97 (out of 102) other passengers in the same section of the plane who agreed to be interviewed.

Conclusions A low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

 

And lastly, a long hard look at attempts by countries to detect and isolate infected travelers during a pandemic. As countries discovered in 2009, travel restrictions are very difficult to implement, and will likely fail in the long run.

 

 

Travel-Associated H1N1 Influenza in Singapore

(Thermal Imaging in 2003)

The idea sounds simple. 

By screening passengers for fever when they arrive via airplane (or boat or train) from another country you can hopefully reduce the number of infected passengers that enter during a pandemic.

 

In reality, it isn’t simple at all.

 

Today a summary from NEJM Journal Watch of a new study that has been published, ahead of print, in the CDC’s  EID Journal  entitled:

 

Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore. Emerg Infect Dis 2010 Jan; [e-pub ahead of print]. Mukherjee P et al

Travel-Associated H1N1 Influenza in Singapore

Airport thermal scanners detected only 12% of travel-associated flu cases; many travelers boarded flights despite symptoms.

Travelers play a key role in spreading many infections, including influenza. Such was the case with the spread of 2009 H1N1 influenza to Singapore, a major travel hub serving 37 million air passengers annually.

(Continue . . .)

New Zealand : Airline Passengers Quarantined

 

 

 

# 6136

 

On an otherwise quiet Sunday afternoon here in the states, news wires are carrying reports of a Boeing 777-200 inbound from Japan that has landed at Auckland’s airport with roughly 60 passengers exhibiting flu-like symptoms.

 

While this sounds like the opening scene to a pandemic disaster movie, in all likelihood this will sorted out to be standard H3N2 influenza which is currently spreading across much of Japan. 

 

The sudden onset of so many cases during this flight has obviously set off alarm bells for local health authorities, however.

 

New Zealand has developed one of the most aggressive airport disease surveillance and interdiction systems in the world. 

 

For now, local media is reporting that all 274 passengers remain on the plane, and health authorities are setting up some sort of quarantine.

 

A couple of reports:

 

First from TVNZ

 

Health scare at Auckland Airport

breaking news

Published: 9:48AM Monday February 13, 2012

A major health response is under way after an Air New Zealand plane landed at Auckland Airport with children with flu-like symptoms on-board.

 

A group of 60 passengers arrived into Auckland off NZ90 from Narita, Tokyo, this morning with the symptoms.

 

Air New Zealand is following public health procedures and has advised the Auckland Regional Public Health Service.

(Continue . . .)

And this report from 3News New Zealand.

 

Flu-like symptoms on Air NZ Tokyo flight

By 3 News online staff

Sixty passengers arriving at Auckland International Airport this morning have reported flu-like symptoms, Air New Zealand has confirmed.

 

Flight NZ90 from Tokyo landed a short time ago and passengers remaining on the plane could be seen on the plane wearing face masks.

(Continue . . . )

 

 

While the odds favor this outbreak turning out to be something fairly mundane, I’ll keep an eye on it and update this blog if I hear more.

BMJ: Flu Transmission Risks On Airplanes

 

 

 

# 4586

 

 

Two years ago I flew to Washington D.C. - during flu season - to attend an HHS sponsored pandemic exercise.  

 

I changed planes in Atlanta coming and going (if you die anywhere in the southeast, no matter what your final destination, you apparently have to go through Atlanta), and spent nearly 10 hours wedged into economy class seating.  

 

All around me, people were coughing and sneezing. And you guessed it, 48 hours after my return, I was down with a nasty flu-like illness.  

Whether I picked up my virus in the confines of the plane, or at the flu conference (irony being what it is), or simply waiting in the airport terminal is something I’ll never know.  

 

But I have my suspicions.

 

Which brings us to a study which appears in the BMJ today, entitled:

 

BMJ 2010;340:c2424

Research

Transmission of pandemic A/H1N1 2009 influenza on passenger aircraft: retrospective cohort study

Michael G Baker, associate professor¹, Craig N Thornley, medical officer of health², Clair Mills, senior lecturer³, Sally Roberts, microbiologist⁴, Shanika Perera, medical officer of health², Julia Peters, medical officer of health², Anne Kelso, director⁵, Ian Barr, deputy director⁵, Nick Wilson, associate professor¹

I’ve reproduced portions of the abstract below.  The entire study is available online at the BMJ.

Objectives To assess the risk of transmission of pandemic A/H1N1 2009 influenza (pandemic A/H1N1) from an infected high school group to other passengers on an airline flight and the effectiveness of screening and follow-up of exposed passengers.

 

Design Retrospective cohort investigation using a questionnaire administered to passengers and laboratory investigation of those with symptoms.

 

Setting Auckland, New Zealand, with national and international follow-up of passengers.

Participants Passengers seated in the rear section of a Boeing 747-400 long haul flight that arrived on 25 April 2009, including a group of 24 students and teachers and 97 (out of 102) other passengers in the same section of the plane who agreed to be interviewed.

 
Main outcome measures Laboratory confirmed pandemic A/H1N1 infection in susceptible passengers within 3.2 days of arrival; sensitivity and specificity of influenza symptoms for confirmed infection; and completeness and timeliness of contact tracing.

 
Results Nine members of the school group were laboratory confirmed cases of pandemic A/H1N1 infection and had symptoms during the flight.

Two other passengers developed confirmed pandemic A/H1N1 infection, 12 and 48 hours after the flight. They reported no other potential sources of infection. Their seating was within two rows of infected passengers, implying a risk of infection of about 3.5% for the 57 passengers in those rows.

All but one of the confirmed pandemic A/H1N1 infected travellers reported cough, but more complex definitions of influenza cases had relatively low sensitivity. Rigorous follow-up by public health workers located 93% of passengers, but only 52% were contacted within 72 hours of arrival.

 
Conclusions A low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

 

 

No real surprises here, of course, except perhaps that fewer people were infected during this flight than one might have expected.  Of course, the usual caveats apply;  this is one study, of one flight, and is specific to the novel H1N1 virus.  

 

The report summarizes what this research adds to what we know this way:

 

What is already known on this topic

Respiratory agents may be transmitted during airline travel, although the level of risk is poorly defined for most agents, including influenza

 

Screening for influenza is difficult because symptoms are variable and may be mild or absent

 

Very little evidence exists on the best way to follow up arriving travellers who might have been exposed to influenza during a flight

What this study adds

A low but measurable risk of contracting influenza from infected travellers with symptoms exists during a long haul flight and is concentrated within two rows of infected travellers

 

Screening for people infected with influenza is likely to be more sensitive if it uses the presence of single symptoms such as cough, rather than more complex case definitions

 

Identification and management of passengers exposed to infections during a flight should be started before passengers leave the airport or board other flights

Fluing The Friendly Skies (Revisited)

 

 

# 4230

 

 

Six weeks before last Spring’s outbreak of novel H1N1 in Mexico and California, I wrote a blog entitled:

 

 

Sunday, March 08, 2009

How The Next Pandemic Will Arrive

# 2876

There is a lot we don't currently know about the next pandemic.  We don't know when it will arrive.  We don't know what virus will cause it.  And we don't know how bad it will be.

 

But there is one thing almost certain.

 

It will arrive in most countries by airplane.

 

 

The video above, which as been making the rounds for several months, was made by ZHAW (Zürcher Hochschule für Angewandte Wissenschaften) or The Zurich University of Applied Sciences.

(Continue . . .)

 

 

Granted, this essay was mostly inspired by finding the youtube video above . . . But timing is everything . . .

 

And as it turned out, college students returning from Spring Break in Mexico were credited – in large part - for the rapid world-wide spread of the H1N1 virus last spring. 

 

This is the price we pay for global commerce and travel.  A greater vulnerability to rapidly spreading pathogens.   

What has been less clear is how much transmission of an influenza virus takes place during an airline flight. 

 

We’ve heard airline reassurances about HEPA filtering, and the number of air exchanges per hour in the passenger cabin, but instinctively most of us suspect that jamming a couple of hundred people into a plane like sardines must entail some infection risks.

 

Today, researchers at UCLA have quantified that risk.  And as one might expect, the denser the seating arrangement (economy class), the better chance of viral transmission. 

 

This from the UCLA Newsroom.

 

 

Study finds H1N1 virus spreads easily by plane

Your best bet? Avoid economy and fly first class, UCLA researchers say

 

By Mark Wheeler January 06, 2010 Category: Health Sciences, Research

 

Viruses love plane travel. They get to fly around the world inside a closed container while their infected carrier breathes and coughs, spreading pathogens to other passengers, either by direct contact or through the air. And once people deplane, the virus can spread to other geographical areas.

 

Scientists already know that smallpox, measles, tuberculosis, seasonal influenza and severe acute respiratory syndrome (SARS) can be transmitted during commercial flights. Now, in the first study to predict the number of H1N1 flu infections that could occur during a flight, UCLA researchers found that transmission during transatlantic travel could be fairly high.

 

Reporting in the current online edition of the journal BMC Medicine, Sally Blower, director of the Center for Biomedical Modeling at the Semel Institute for Neuroscience and Human Behavior at UCLA, along with Bradley Wagner and Brian Coburn, postdoctoral fellows in Blower's research group, used novel mathematical modeling techniques to predict in-flight transmission of the H1N1 virus.

 

They found that transmission could be rather significant, particularly during long flights, if the infected individual travels in economy class. Specifically, two to five infections could occur during a five-hour flight, five to 10 during an 11-hour flight, and seven to 17 during a 17-hour flight.

 

"Clearly, it was air travel, by transporting infectious individuals from the epicenter in Mexico to other geographic locations, that significantly affected the spread of H1N1 during the outbreak last spring," Coburn said. "However, until our study, it hadn't been determined how important in-flight transmission could be. Therefore, we decided to make a mathematical model and predict what could be expected to occur during a flight."

 

(Continue. . . )

 

 

There is obviously very little you can do to protect yourself from influenza during a prolonged flight if the person seated next to you is infected with the virus.

Very little, except of course, getting the flu vaccine every year.

 

There’s always that.