Grand Rounds: Preventing Aedes Mosquito-Borne Diseases

 

# 10,049

 

Each month the CDC holds a Grand Rounds web presentation that focuses on a single health-related issue.  In the past I’ve highlighted their broadcasts on such diverse topics as Multidrug-Resistant Gonorrhea, Childhood Emergency Preparedness, and Discovering New Diseases  . . . to name a few.

 

The CDC maintains an archive of these informative presentations – going back to 2009 – which you can access at Grand Rounds – Archives.  Highly recommended.

 

With summer almost here, and both Chikungunya and Dengue spreading extensively in the Caribbean and Central and South America, these mosquito borne diseases may be on the verge of making inroads into North America. All of which makes the timing of next week’s presentation fortuitous. 

 

First details on Tuesday’s event, then I’ll be back with more on the arbovirus disease threats to the United States.

 

Dengue and Chikungunya in Our Backyard: Preventing Aedes Mosquito-Borne Disease

 

Webcast Links

Windows Media:
http://wm.onlinevideoservice.com/CDC1

Flash:
http://www.onlinevideoservice.com/clients/CDC/?mount=CDC3

Captions are only available on the Windows Media links. The webcast links are only active during the date and time of the session, but all sessions are archived for future viewing.

Tuesday, May 19 at 1pm EDT

Aedes aegypti and Aedes albopictus mosquitoes are the primary vectors for dengue, chikungunya, yellow fever, and Zika viruses. Taken together, these viruses account for almost 100 million cases of mosquito-borne disease per year. Globally, dengue is the most important mosquito-borne viral disease. In the last 50 years, incidence has increased 30-fold by expanding into new countries and new areas. Chikungunya often occurs in large outbreaks with high infection rates, affecting more than a third of the population in areas where the virus is circulating. In 2014, more than a million cases were reported worldwide. While Chikungunya disease rarely results in death, the symptoms can be severe and disabling.

Outbreaks of mosquito-borne diseases depend on many factors and are especially difficult to predict, prevent and control. Because there are no licensed vaccines available to prevent dengue or chikungunya, controlling mosquito populations and reducing bites are currently the most effective prevention measures.

This session of Grand Rounds will highlight the importance of preventing Aedes mosquito-borne diseases and the need for improved diagnostic, prevention and control measures.

Presented By:

Marc Fischer, MD, MPH
Chief, Surveillance and Epidemiology Activity, Arboviral Diseases Branch
Division of Vector-Borne Diseases
National Center for Emerging and Zoonotic Infectious Diseases, CDC
"Dengue, Chikungunya and Other Aedes Mosquito-Borne Diseases"

Thomas W. Scott, PhD
Professor and Director, Vector-Borne Disease Laboratory
Department of Entomology and Nematology
University of California, Davis
"The Status and Frontiers of Vector Control"

Harold Margolis, MD
Branch Chief, Dengue Branch
Division of Vector-Borne Diseases
National Center for Emerging and Zoonotic Infectious Diseases, CDC
"Prevention Strategies for Aedes Mosquito-Borne Diseases"

Facilitated By:

John Iskander, MD, MPH, Scientific Director, Public Health Grand Rounds
Phoebe Thorpe, MD, MPH, Deputy Scientific Director, Public Health Grand Rounds
Susan Laird, MSN, RN, Communications Director, Public Health Grand Rounds

Although Dengue and Chikungunya now regularly arrive in the North America via infected (viremic) travelers, we’ve been lucky in that neither has had much success in entrenching itself into our local mosquito populations. 

 

How long our luck will hold is anyone’s guess.  West Nile Virus, which emerged in NYC in 1999, quickly spread across the nation and is now a perennial threat.

 

Chikungunya was introduced by viremic travelers to the Caribbean in the fall of 2013, who inadvertently `seeded’ the virus into the local mosquito population.  Over the past 18 months there have been well over 1.4 million infections in the Americas – spanning more than 3 dozen nations - and millions more will undoubtedly be infected in the years to come.  

Dengue arrived in South Florida in 2009 in a similar fashion (see MMWR: Dengue Fever In Key West), as did West Nile Virus to NYC in the late 1990s.  So far, Dengue and Chikungunya have had only very limited success spreading in the United States. Literally only a handful of cases have been reported thus far.

 

But as we’ve seen with West Nile Virus - when the right combination of multiple virus introductions, competent vectors, and favorable environmental conditions come together - formerly exotic diseases can get a foothold and even thrive here in the United States.

 

Right now, Dengue and Chikungunya are minor threats in North America, but that could change quickly. When you add in the other mosquito-borne illnesses (EEE, WNV, SLEV, etc.) it just makes sense to do whatever you can to limit your exposure.

 

Which is why the Florida State Health Department urge residents and visitors to follow the `5 D’s’:

CDC West Nile Virus Update – July 1st

 

 

# 8801

 

The West Nile Virus season is really only just getting started, but so far in 2014 the CDC has been notified of human infections in six states:  Arizona, California, Mississippi, Missouri, South Dakota, and Tennessee.

 

WNV infections in mosquitoes, birds, sentinel animals, or veterinary animals have been reported to CDC’s ArboNET from sixteen additional  states: Alabama, Colorado, Florida, Idaho, Illinois, Indiana, Louisiana, Michigan, Nebraska, New Jersey, New York, Pennsylvania, Tennessee, Texas, Utah, Wisconsin, and Wyoming.

 

Unlike Chikungunya – which primarily affects humans and non-human primates – WNV is primarily a disease of birds.  Humans and horses are considered `incidental’ infections (see WNV vs CHIKV: A Host Of Differences).

 

The least severe form of the disease – West Nile Fever -  probably infects more than 100,000 Americans every year, although most are so mildly affected they have no idea the are infected.

 

Neuroinvasive cases (which present with meningitis, encephalitis, or flaccid Paralysis), while less common, are severe enough that they nearly always result in hospitalization and diagnosis, and so they are considered the best indicator of the scope of each year’s epidemic. 

 

The number of cases varies widely each, with a record of nearly 3,000 cases of neuroinvasive WNV, and 286 deaths reported in 2012.  Last year saw more than a 50% reduction, down to 1247 neuroinvasive cases and 119 deaths. 

 

So far, in 2014 just 6 neuroinvasive cases have been reported, but case reporting tend to lag behind actual events by a week or two, so it is too soon to know what kind of WNV season we will see this year.

 

West Nile isn’t the only arbovirus we keep track of.  Last year – excluding Dengue – the United States also recorded (see West Nile Virus and Other Arboviral Diseases — United States, 2013):

• 2,469 cases of WNV disease
• 85 cases of La Crosse virus (LACV)
• 22 cases of Jamestown Canyon virus (JCV
• 15 cases of Powassan virus (POWV)
• 8 cases of eastern equine encephalitis virus (EEEV)

To this mix we can add a smattering of locally acquired Dengue in Florida and Texas, with the added threat that this year (or next) Chikungunya will likely make its way into the local mosquito population as well (see Study: Chikungunya’s Growing Threat To The Americas).

.  

While the odds of contracting a serious illness from mosquito bites in the United States remains very low – they are increasing with the addition of new arboviral threats – so if you visit or live in mosquito territory – it is worth remembering Florida Department of Health’s, (FDOH) recommendation that individuals protect themselves by following the “5 D’s”.

MMWR: West Nile & Other Arboviral Diseases — United States, 2013

Credit CDC

 

# 8765

 

As the chart above indicates, even before West Nile arrived in 1999, North America already had a relatively long list of major mosquito-borne encephalopathies to deal with; SLE (St. Louis Encephalitis), EEE (Eastern Equine Encephalitis), WEE (Western Equine Encephalitis), LAC (LaCrosse Virus), and POW (Powassan Encephalitis).

 

While the number of human infections each year was relatively low, what we lacked for in patient counts we made up for in variety.  

 

To these neuroinvasive (i.e., meningitis, encephalitis, or acute flaccid paralysis producing) arboviruses we can add additional mosquito-borne diseases such as dengue, malaria, and the new threat on the block; Chikungunya. While North America is hardly a hotbed of mosquito borne diseases, they are decidedly less rare today than they were two or three decades ago.

 

And given the regular importation of new vector-borne diseases via international travelers, this seems to be a trend likely to continue (see The Global Reach Of Infectious Disease).

.

 

Yesterday the CDC’s MMWR published an update on the 2013 West Nile/Arbovirus season (excluding dengue).  While far from being the worst year we’ve seen (WNV was down by about 50% over 2012), 2013 provided its fair share of arboviral misery. 

• 2,469 cases of WNV disease
• 85 cases of La Crosse virus (LACV)
• 22 cases of Jamestown Canyon virus (JCV
• 15 cases of Powassan virus (POWV)
• 8 cases of eastern equine encephalitis virus (EEEV)

 

Despite the reputation for Florida and the Southeastern states as being a mosquito haven, those states ranked among the lowest in reports of neuroinvasive WN disease.

Incidence* of reported cases of West Nile virus neuroinvasive disease, by state — United States, 2013

 

It is too soon to know what kind of year 2014 will be for mosquito-borne diseases in North America. With both dengue and chikungunya threatening to make inroads, this year’s mosquito season will be watched closely across the country. In the meantime, some excerpts from last year’s surveillance report below, but follow the link to read it in its entirety.

 

 

West Nile Virus and Other Arboviral Diseases — United States, 2013

Weekly

June 20, 2014 / 63(24);521-526

Nicole P. Lindsey, MS1, Jennifer A. Lehman1, J. Erin Staples, MD1, Marc Fischer, MD1 (Author affiliations at end of text)

Arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. West Nile virus (WNV) is the leading cause of domestically acquired arboviral disease in the United States (1). However, several other arboviruses also cause sporadic cases and seasonal outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, and acute flaccid paralysis) (1). This report summarizes surveillance data reported to CDC in 2013 for WNV and other nationally notifiable arboviruses, excluding dengue. Forty-seven states and the District of Columbia reported 2,469 cases of WNV disease. Of these, 1,267 (51%) were classified as WNV neuroinvasive disease, for a national incidence of 0.40 per 100,000 population. After WNV, the next most commonly reported cause of arboviral disease was La Crosse virus (LACV) (85 cases), followed by Jamestown Canyon virus (JCV) (22), Powassan virus (POWV) (15), and eastern equine encephalitis virus (EEEV) (eight). WNV and other arboviruses continue to cause serious illness in substantial numbers of persons annually. Maintaining surveillance remains important to help direct and promote prevention activities.

<SNIP>

Discussion

In 2013, WNV was the most common cause of neuroinvasive arboviral disease in the United States. However, LACV was the most common cause of neuroinvasive arboviral disease among children. More JCV cases were reported in 2013 than in any previous year and included the first cases reported from eight states. This increase is likely related to the initiation of routine immunoglobulin M testing for JCV at CDC in 2013 and suggests that the incidence of JCV infection in prior years might have been underestimated. EEEV disease, although rare, remained the most severe arboviral disease, with four deaths among eight patients. More than 90% of arboviral disease cases occurred during April–September, emphasizing the importance of focusing public health interventions during this period.

Reported numbers of arboviral disease cases vary from year to year. Weather (e.g., temperature and precipitation), zoonotic host and vector abundance, and human behavior (e.g., repellent use, outdoor activities, and use of air conditioning or screens in the home) are all factors that can influence when and where outbreaks occur. This complex ecology makes it difficult to predict how many cases of disease might occur in the future and where they will occur. Increased numbers of reported cases and the identification of cases in new locations might reflect actual changes in incidence and epidemiology or increased disease awareness.

The incidence of WNV neuroinvasive disease declined substantially in 2013 (incidence of 0.40 per 100,000 population) compared with 2012 (0.92 per 100,000 population), when a large multistate outbreak occurred, with incidence nearing the levels observed in 2002 and 2003 (4). However, the incidence in 2013 was similar to that during 2004–2007 (median = 0.43; range = 0.39–0.50) and was higher than that during 2008–2011 (median = 0.18; range: 0.13–0.23) (3–5). WNV activity remained focalized in 2013, with more than half of the neuroinvasive disease cases being reported from just six states.

The findings in this report are subject to at least two limitations. First, ArboNET is a passive surveillance system that relies on clinicians to consider the diagnosis of an arboviral disease and obtain appropriate diagnostic tests, and on health-care providers and laboratories to report laboratory-confirmed cases to public health authorities. Second, testing and reporting are incomplete, leading to a substantial underestimate of the actual number of cases (6). For example, data from previous studies suggest there are 30–70 nonneuroinvasive disease cases for every reported case of WNV neuroinvasive disease (7–9). Extrapolating from the 1,267 WNV neuroinvasive disease cases reported, an estimated 38,000–88,500 nonneuroinvasive disease cases might have occurred in 2013. However, only 1,202 (1%–3%) were diagnosed and reported.

Arboviruses continue to cause substantial morbidity in the United States. However, cases occur sporadically, and the epidemiology varies by virus and geographic area. Surveillance is essential to identify outbreaks and guide prevention efforts aimed at reducing the incidence of these diseases. Health-care providers should consider arboviral infections in the differential diagnosis of cases of aseptic meningitis and encephalitis, obtain appropriate specimens for laboratory testing, and promptly report cases to public health authorities (2). Because human vaccines against domestic arboviruses are not available, prevention of arboviral disease depends on community and household efforts to reduce vector populations (e.g., applying insecticides and reducing mosquito breeding sites), personal protective measures to decrease exposure to mosquitoes and ticks (e.g., use of repellents and wearing protective clothing), and screening blood donors.

Acknowledgment

ArboNET surveillance coordinators in state and local health departments.

(Continue . . . )

 

Florida Surveillance: Imported Chikungunya, Dengue, Malaria

Source Florida Arbovirus Surveillance – Week 24

 

# 8754

 

If you want to gauge the latest fashion trends, you go to Paris.  If you are looking for the latest in bleeding edge technology, you go to Silicon Valley. But if you are interested in monitoring imported mosquito-borne disease threats to the United States, the place to pitch your tent is Florida. 

With well over 80 million visitors each year, Florida is the top travel destination in the world.  

 

And many of those travelers come from places around the world where dengue, malaria, and chikungunya are endemic. Which means that nearly every week, some number of infected travelers unpack their bags in Florida.

 

Up until 2009, Florida had kept dengue at bay for  6 decades.  But one (or likely, more) infected international travelers arrived in Key West, and the virus jumped into the local mosquito population (see MMWR: Dengue Fever In Key West).

 

Since then, we’ve seen sporadic locally acquired dengue cases in south Florida(see Florida: Dengue Forces Suspension Of Blood Donations In Two Counties), likely due to repeated `reseeding’ of the virus among local mosquito populations.

The concern is, that the same thing could happen with malaria, or the recently emerged Chikungunya virus, which is now exploding across the Caribbean.

 

In 2013, Florida recorded 120 imported cases of Dengue (plus 23 locally acquired cases), 53 imported cases of malaria (0 local cases), and 0 imported cases of Chikungunya.  

 

Today, the Florida Department of Health’s weekly Arbovirus surveillance report – Week 24 has come out, and we find – while no locally transmitted cases have been reported – travel associated dengue, malaria, and chikungunya cases continue to rise.

 

Over the past week, four new malaria importations, and 17 new Chikungunya importations were reported.

 

International Travel-Associated Dengue Fever Cases: Twenty-four cases of dengue with onset in 2014 have been reported in individuals with travel history to a dengue endemic country in the two weeks prior to onset. Countries of origin were: Bolivia, Brazil (2), Caribbean, Cuba (8), Dominican Republic (4), Guadeloupe, Honduras, Puerto Rico (3), Trinidad, and Venezuela (2). Counties reporting cases were: Alachua, Broward (2), Clay, Hillsborough (3), Marion, Miami-Dade (10), Orange, Osceola (3), Pinellas, and Seminole. Four of the cases were reported in non-Florida residents.

In 2014, 16 of the 24 cases of dengue reported in Florida have been serotyped by PCR. Additional serotyping and strain typing are being conducted.

 

International Travel-Associated Chikungunya Fever Cases: Forty-two cases of chikungunya with onset in 2014 have been reported in individuals with travel history to a chikungunya endemic country or area experiencing an outbreak in the two weeks prior to onset. Countries of origin were: Dominica, Dominican Republic (8), Haiti (31), and Martinique (2). Counties reporting cases were: Brevard, Broward (7), Charlotte, Clay, Duval (2), Flagler, Hillsborough (3), Lake, Lee, Leon, Miami-Dade (7), Orange (3), Osceola, Palm Beach (7), Pasco, Santa Rosa, Seminole, St. Lucie, and Volusia. Eight of the cases were reported in non-Florida residents.

International Travel-Associated Malaria Cases:  Eighteen cases of malaria with onset in 2014 have been reported. Countries of origin were: Angola, Dominican Republic, Equatorial New Guinea (2), Ghana, Guatemala, India, Ivory Coast (2), Kenya, Sierra Leone (4), Sudan, Uganda (2), and multiple sub-Saharan African countries (1). Counties reporting cases were: Broward (4), Duval, Escambia, Hernando, Hillsborough (3), Miami-Dade (2), Okaloosa, Orange, Osceola, Palm Beach, Pasco, and Santa Rosa. Two of the cases were reported in non-Florida residents.

Thirteen cases (72%) were diagnosed with Plasmodium falciparum. Three cases (17%) were diagnosed with Plasmodium vivax.One case (5.5%) was diagnosed with Plasmodium malariae. One case (5.5%) was diagnosed with Plasmodium Ovale.

 

 

The good news is, despite repeated introductions this spring, we’ve not seen any local transmission of these mosquito-borne diseases in Florida. The not-quite-so-good news is our mosquito season is really just getting started.

 

While there are no vaccines available for these viruses, these are still largely preventable diseases. Local Health departments urge people to always follow the `5 D’s’ of prevention:

COCA Call On Chikungunya – Tomorrow, Feb 18th

Credit CDC

 

# 8305

 

As a native Floridian, I’m understandably very interested in arboviruses; those spread by arthropods (ie. Mosquitoes, ticks, sandflies, etc.).  Each year I devote considerable blog space to West Nile Virus, Dengue Fever, EEE, and various tick and mosquito borne encephalitis-type illnesses.

 

In 2005, an old arbovirus called Chikungunya – previously only found in Africa – emerged on the world stage and quickly spread across the Indian Ocean, infecting hundreds of thousands of people.  While rarely fatal, this painful mosquito transmitted infection can can cause long-term arthritic-like disabilities.

 

Up until three months ago, the virus had never been acquired in the Americas, although imported cases among tourists or returning travelers was not uncommon. 

 

In November, we saw the first outbreak of the disease in the Caribbean (see CDC Update On Chikungunya In The Caribbean), which has continued to expand over the winter. Two years ago, the arrival of this virus to the Western Hemisphere was predicted in the CDC/PAHO document Preparedness and Response for Chikungunya Virus Introduction in the Americas.

 

In December, we saw a CDC HAN Advisory On Recognizing & Treating Chikungunya Infection, as concerns mount that we could see the virus begin to filter into the United States, and tomorrow  the CDC will hold a COCA call for clinicians on emerging arbovirus.

 

Although primarily of interest to clinicians, the CDC holds frequent COCA (Clinician Outreach Communication Activity) calls which are designed to ensure that practitioners have up-to-date information for their practices.

 

Details of tomorrow’s conference call follow:

 

Chikungunya Virus – An Emerging Threat to the Americas

= Free Continuing Education

Date: Tuesday, February 18, 2014

Time: 2:00 - 3:00 pm (Eastern Time)

To Join:

Dial-In: 888-233-9077 (U.S. Callers)
              773-799-3915 (International Callers)

Passcode:8291522

Access Webinar: https://www.mymeetings.com/nc/join.php?i=PW4203438&p=8291522&t=c

Presenter(s):

J. Erin Staples, MD, PhD
Medical Epidemiologist
Arboviral Diseases Branch
National Center for Emerging and Zoonotic Infectious Diseases
Centers for Disease Control and Prevention

Overview:

Chikungunya virus is a mosquito-borne virus that can cause fever and severe polyarthralgia. Outbreaks of the chikungunya have occurred in countries in Africa, Asia, Europe, and the Indian and Pacific Oceans. In late 2013, the first local chikungunya virus transmission in the Americas was reported on islands in the Caribbean. Travelers to areas with ongoing outbreaks are at risk of becoming infected and spreading the virus to new areas, including the United States. During this COCA call, a CDC subject matter expert will provide information on chikungunya virus epidemiology, clinical findings, diagnosis, treatment, and prevention. Additionally, they will describe the importance of early recognition and reporting of suspected cases to mitigate the risk of local transmission.

 

 

For some earlier blog posts on Chikungunya and other related arboviruses, you may wish to revisit:

 

WNV: The Economic Costs Of An Invasive Arbovirus

ECDC Update On The Spread Of Chikungunya In The Caribbean

Florida: Dengue Forces Suspension Of Blood Donations In Two Counties

The Risks Of Chikungunya Outbreaks In The United States

EEE: Eastern Equine Encephalitis

 

# 6501

 

While West Nile Virus is making headlines in Texas and across much of the nation, another mosquito-borne virus – EEE (Eastern Equine Encephalitis) – has the attention of Massachusetts health officials.

 

On Thursday, the Massachusetts Department of Health & Human Services released the following alert:

 

State Health Officials Raise EEE Threat Level in Two Communities after Detection of EEE-Positive Mosquitoes

New Bedford and Westborough raised to High; ground spraying to be enhanced

BOSTON — Thursday, August 16, 2012 – The Massachusetts Department of Public Health (DPH) today announced the detection of mammal-biting mosquitoes infected with Eastern Equine Encephalitis (EEE) in New Bedford and Westborough. As a result, health officials have raised the EEE threat level to “High” in these two communities and recommend that outdoor evening events are curtailed there for the remainder of the summer. Ground-based spraying by mosquito control projects is ongoing in both New Bedford and Westborough and will be enhanced.

(Continue. . . )

 

 

So far, only one human case of EEE has been detected in Massachusetts this year, and that one is believed to have been acquired out of state. This risk of seeing additional cases, however, is deemed high in communities where human-biting mosquitoes are found to carry the virus.

 

Although far less common than West Nile Virus, EEE is of concern because it has a high fatality rate (35%), and among the survivors, a large number suffer ongoing neurological problems.

 

Over the past decade there have been an average of about 7 cases (not deaths) of `Triple E’ in the United States each year (range range: 3—21), which makes EEE an exceedingly rare disease in humans.

 

But given its severity (and the co-circulation of other mosquito borne diseases like West Nile, La Cross Virus, & SLEV), it makes sense to take steps to protect against mosquito bites – even if your local officials have not issued a warning.

 

The Florida Department of Health’s advice to protect  against mosquito borne diseases is that people should practice the "5 D's"

Don't go outdoors at DUSK and DAWN when mosquitoes are most active.

DRESS so your skin is covered with clothing

Apply mosquito repellent containing DEET to bare skin and clothing. 

Other effective repellents include picaridin, oil of lemon eucalyptus, and IR3535

Empty containers and DRAIN standing water around your home where mosquitoes can lay eggs.

 

 

While the number of yearly cases is low, the distribution of EEE in the United States far ranging.

 

The natural host for the EEE virus are songbirds, which can become infected usually without suffering ill effect.  The virus is spread among these birds by the blood feeding of female mosquitoes (males don’t bite).

 

After an infected mosquito feeds on a bird, the bird becomes infected and the virus begins reproducing. After a few days, and for only a few days, the bird’s bloodstream amplifies the virus enough to infect subsequent mosquitoes that feed on it.

 

Culiseta melanura, which means "curly black hairs", is the species of swamp mosquito that serves as the primary vector for this virus among birds.

 

Culiseta melanura, however, isn’t usually attracted to humans.

 

So it generally requires a secondary type of mosquito - one that isn’t quite as picky a feeder - such as the Aedes albopictus or  Coquillettidia perturbans  `salt and pepper’ mosquito, to bite an infected bird in order to move it into the equine or human population.

 

The Transmission cycle is illustrated by the following graphic from the CDC.

 

Humans and horses don’t develop a high enough viral EEE titer in their bloodstream to pass on the virus if they are subsequently bitten by a mosquito, so they are considered to be `dead-end hosts’.

 

 

As there is no vaccine against EEE, the best tactic is prevention, and high in that category is the use of mosquito repellants.

 

To help you with choosing the right repellant the EPA has developed an interactive insect repellant search engine that will that will allow you to input your needs and it will spit out the best repellants to use.

 

(click image to go to search engine)

 

 

For more on Arboviruses in the United States you may wish to revisit this blog from last year:

 

MMWR: Arboviral Disease Surveillance – 2010

MMWR: Arboviral Disease Surveillance – 2010

 

 

# 5738

 

 

Arboviruses belong to a large group of viruses carried and transmitted by biting mosquitoes, ticks, and other arthropods when they take a blood meal from susceptible vertebrate hosts.

 

The map below shows the global distribution of some of the more common encephalitis producing arboviruses.

 

 

A few of my blogs from last year on these viral threats included:

 

EEE Reports In Michigan And R.I.

Florida Records 4th EEE Death In July

ASTMH: Dengue and Insect-Borne EIDs In The US

Eastern Equine Encephalitis (EEE)

 

This week the CDC’s MMWR contains a surveillance report on arthropod-borne viruses – or arboviral - infections (excluding Dengue which is tracked separately) in the United States during 2010.

 

And last year, it turns out, was a banner year for arboviral disease in the United States, with the number of West Nile Virus (WNV) cases (1,021) up sharply over 2009, and 62% of those producing neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis).

 

Other viral players included California serogroup viruses (CALV), eastern equine encephalitis virus (EEEV),  St. Louis encephalitis virus (SLEV) and Powassan virus (POWV).

 

 

A few excerpts from the report follow (slightly reformatted for readability). Follow the link to read it in its entirety.

 

West Nile Virus Disease and Other Arboviral Diseases --- United States, 2010

Weekly

August 5, 2011 / 60(30);1009-1013

Arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. Since West Nile virus (WNV) was first detected in the Western Hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the United States (1).

 

However, several other arboviruses continue to cause sporadic cases and seasonal outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis) (1,2).

 

This report summarizes surveillance data reported to CDC in 2010 for WNV and other nationally notifiable arboviruses (excluding dengue, which is reported separately).

 

In 2010, 40 states and the District of Columbia (DC) reported 1,021 cases of WNV disease. Of these, 629 (62%) were classified as WNV neuroinvasive disease, for a national incidence of 0.20 per 100,000 population. States with the highest incidence were Arizona (1.60), New Mexico (1.03), Nebraska (0.55), and Colorado (0.51).

 

After WNV, the next most commonly reported cause of neuroinvasive arboviral disease was California serogroup viruses (CALV), with 68 cases, followed by eastern equine encephalitis virus (EEEV), 10 cases, St. Louis encephalitis virus (SLEV), eight cases, and Powassan virus (POWV), eight cases. WNV and other arboviruses continue to cause focal outbreaks and severe illness in substantial numbers of persons in the United States. Maintaining surveillance remains important to guide arboviral disease prevention activities.

 

(Continue . . . )

Given the limitations of surveillance, and the fact that many people experience mild, or non-specific symptoms of infection, the true burden of these (mostly) mosquito borne viruses in the United States can only be estimated.

 

The editorial note to this report states:

 

Detection and reporting are incomplete, leading to a substantial underestimate of the actual number of cases. Based on previous studies, for every case of WNV neuroinvasive disease, approximately 140 human WNV infections occur, with 80% of infected persons remaining asymptomatic and 20% developing nonneuroinvasive disease (7,8).

Extrapolating from the 629 reported WNV neuroinvasive disease cases, an estimated 88,000 infections and 17,600 cases of nonneuroinvasive disease might have occurred in 2010; however, only 392 (2%) nonneuroinvasive disease cases were reported.

 

 

As the chart below indicates, the older adults are more apt to develop neuroinvasive disease from a WNV infection.

FIGURE. Incidence* of cases (N = 629) of West Nile virus neuroinvasive disease,† by age group --- United States, 2010

* Per 100,000 population, based on July 1, 2010, U.S. Census estimates.

† Meningitis, encephalitis, or acute flaccid paralysis.

 

 

A summation of the report reads:

What is already known on this topic?

Since West Nile virus (WNV) was first detected in the Western Hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the United States. However, several other arboviruses can cause sporadic cases and seasonal outbreaks of neuroinvasive disease.

What is added by this report?

WNV was the most common cause of neuroinvasive arboviral diseases in the United States in 2010; however, La Crosse virus was the most common cause among children. Eastern equine encephalitis, although rare, remained the most severe arboviral disease, with a 50% case-fatality rate.

What are the implications for public health practice?

WNV and other arboviruses continue to be a source of severe illness each year for substantial numbers of persons in the United States. Maintaining surveillance remains important to help direct and promote prevention activities.

 

 

While the odds of contracting a serious illness from mosquito bites in the United States remains very low - if you visit or live in mosquito territory – it is worth remembering Florida Department of Health’s, (FDOH)
recommendation that individuals protect themselves by following the “5 D’s”.

Minnesota: Powassan Virus Fatality

 

 

(Photo Credit- CDC)

# 5663

 

 

News today of the first known death in the state of Minnesota from the Powassan Virus (POW), a rare but sometimes deadly Flavivirus  in the same family of arboviruses  as West Nile Virus (WNV), Dengue Fever, St. Louis Encephalitis, and Yellow Fever.

 

Minnesota’s  Department of Health has details on this fatality in the press release below, after which I’ll return with more on this rare infection.

 

 

News Release
June 29, 2011

Minnesota records first death from tick-borne Powassan virus

State health officials emphasize the importance of preventing tick bites

 

A woman in her 60s from northern Minnesota has died from a brain infection due to Powassan (POW) virus. This is the first death in the state attributed to the disease. One other likely POW case has been identified this year in Minnesota, in an Anoka County man in his 60s who was hospitalized with a brain infection and is now recovering at home. POW virus is transmitted through the bite of an infected tick.

 

Both 2011 cases became ill in May after spending time outdoors and noticing tick bites. The fatal case was likely exposed to ticks near her home. The case from Anoka County might have been exposed near his home or at a cabin in northern Minnesota.

 

Health officials say this death serves as a reminder of the vital importance of preventing tick bites. “Although Powassan cases are rarely identified, it is a severe disease which is fatal in about 10 percent of cases nationwide, and survivors may have long-term neurological problems” said Dr. Ruth Lynfield, state epidemiologist with the Minnesota Department of Health (MDH).

 

“Powassan disease is caused by a virus and is not treatable with antibiotics, so preventing tick bites is crucial.”

(Continue . . . )

 

The Powassan Virus (POW) was first identified in 1958 in Powassan, Ontario following the death of a child from the infection.  Later, a species of ticks (Dermacentor andersoni) collected in Colorado in 1952 were shown to carry the same virus.

 

The virus can be transmitted by the same species of ticks that carry Lyme disease, anaplasmosis, and babesiosis (bacterial or parasitic infections).

 

The animal reservoir for the virus appears to encompass a wide range of mammals. According to the Canadian Cooperative Wildlife Health Center the virus has been identified with:

 

. . . the Woodchuck (Marmota monax) and the tick Ixodes cookei seem to be particularly important, but infection rates can be high in Red Squirrels (Tamiasciurus hudsonicus), Grey Squirrels (Sciurus carolinensis), Eastern Chipmunks (Tamias striatus), Porcupines (Erethizon dorsatum), Deer Mice (Peromyscus maniculatus), voles (Microtus sp.), Snowshoe Hares (Lepus americanus), Striped Skunks (Mephitis mephitis) and Raccoons (Procyon lotor).

 

Human POW infection appears to be very rare, but difficulties in testing, the variability of illness severity, and similarity of symptoms to other illnesses may be clouding that picture.

 

The Minnesota Department of Health advises:

 

How common is POW disease?

Physician-diagnosed POW disease is very rare. Fewer than 60 cases have been identified in the U.S. and Canada since 1958. From 2008-2010, six cases of POW encephalitis or meningitis have been reported in Minnesota. These cases lived in or had visited wooded areas in north central or east central counties (Cass, Carlton, Hubbard, Itasca, or Kanabec).

 

It is possible that other cases of suspected viral encephalitis or meningitis during times of peak tick-borne disease transmission (May to October) are due to POW virus.

 

 

In light of this fatality, the Minnesota Health Department is advising health providers:

 

• Medical providers should consider the possibility of POW virus infection in patients with central nervous system disease who have recent histories of activities in wooded areas (with or without known tick bites) during Minnesota’s warm weather months.
• The only laboratories that offer testing for POW virus are at state health departments (including MDH) and CDC. At this time, no commercial laboratories offer serologic testing for the virus.
• Serum or CSF specimens from patients with central nervous system disease can be submitted directly to the MDH Public Health Laboratory for arboviral disease testing, including POW virus.

 

Complicating matters, the state of Minnesota is facing a potential shutdown of government services at midnight tonight due to a budget impasse that could adversely affect state laboratory testing services.

 

Admittedly, the odds of contracting the Powassan virus are exceedingly low. More people are struck and killed by lightning each year or killed by bee stings.

 

But when you consider the wide panoply of tickborne diseases found in the United States;

 

Lyme disease, anaplasmosis, babesiosis, TBE (tick borne encephalitis), Rocky Mountain Spotted Fever, Ehrlichiosis, STARI (Southern Tick-Associated Rash Illness), Tickborne relapsing fever (TBRF), Rickettsiosis, and Tularemia . . . 

 

. . .  well, the odds of getting sick from a tick bite go up considerably. 

 

Lyme disease alone is considered responsible for 20,000+ infections each year (MMWR  Lyme Disease --- United States, 2003—2005).

 

Which means that preventing tick bites, and looking for and removing ticks as quickly as possible, are important steps to take after visiting tick-endemic areas.

 

Since it is summer, and tick season, a few timely reminders:

 

 

Lastly, the CDC offers the following advice:

 

Preventing Tick Bites

While it is a good idea to take preventive measures against ticks year-round, be extra vigilant in warmer months (April-September) when ticks are most active.

Avoid Direct Contact with Ticks

• Avoid wooded and bushy areas with high grass and leaf litter.
• Walk in the center of trails.

Repel Ticks with DEET or Permethrin

• Use repellents that contain 20% or more DEET (N, N-diethyl-m-toluamide) on the exposed skin for protection that lasts up to several hours. Always follow product instructions. Parents should apply this product to their children, avoiding hands, eyes, and mouth.
• Use products that contain permethrin on clothing. Treat clothing and gear, such as boots, pants, socks and tents. It remains protective through several washings. Pre-treated clothing is available and remains protective for up to 70 washings.
• Other repellents registered by the Environmental Protection Agency (EPA) may be found at http://cfpub.epa.gov/oppref/insect/.

Find and Remove Ticks from Your Body

• Bathe or shower as soon as possible after coming indoors (preferably within two hours) to wash off and more easily find ticks that are crawling on you.
• Conduct a full-body tick check using a hand-held or full-length mirror to view all parts of your body upon return from tick-infested areas. Parents should check their children for ticks under the arms, in and around the ears, inside the belly button, behind the knees, between the legs, around the waist, and especially in their hair.
• Examine gear and pets. Ticks can ride into the home on clothing and pets, then attach to a person later, so carefully examine pets, coats, and day packs. Tumble clothes in a dryer on high heat for an hour to kill remaining ticks.

World Malaria Day

 

 

# 5517

 

 

 

Monday, April 25th is World Malaria Day. 

 

Malaria is mosquito-borne infectious disease caused by a parasite – Plasmodium – and is common in much of the world including Sub-Saharan Africa, Asia and the Americas.  

 

Plasmodium falciparum in human blood – credit wikipedia

 

There are four microscopic protozoan parasites in the genus Plasmodium (P. vivax, P. falciparum, P. malariae and P. ovale) that cause malaria in humans around the world.  Of these Plasmodium falciparum is generally the most serious.

 

The parasites multiply in the liver and infect red blood cells, resulting in recurrent fevers and headaches - and in severe cases - coma and death.

 

Malaria is an extremely serious problem in Africa, where 1 in 5 childhood deaths is due to the disease. According to the WHO’s 10 Facts on Malaria:

 

An African child has on average between 1.6 and 5.4 episodes of malaria fever each year. And every 30 seconds a child dies from malaria.

 

The World Health Organization describes tomorrow’s World Malaria Day this way:

 

World Malaria Day

25 April 2011

In 2009, about 3.3 billion people - half of the world's population - were at risk of malaria. Every year, this leads to about 250 million malaria cases and nearly 800 thousand deaths. People living in the poorest countries are the most vulnerable.

 

World Malaria Day - which was instituted by the World Health Assembly at its 60th session in May 2007 - is a day for recognizing the global effort to provide effective control of malaria. It is an opportunity:

• for countries in the affected regions to learn from each other's experiences and support each other's efforts;
• for new donors to join a global partnership against malaria;
• for research and academic institutions to flag their scientific advances to both experts and general public; and
• for international partners, companies and foundations to showcase their efforts and reflect on how to scale up what has worked.

Related links

• More about World Malaria Day
• Roll Back Malaria Partnership
• WHO Global Malaria Programme
• Topical overview: malaria

 

While there are medicines available to combat the disease, over time the parasites have developed resistance to many of the older drugs. 

According to the WHO:

 

Resistance of Plasmodium falciparum to choloroquine, the cheapest and the most used drug is spreading in almost all the endemic countries.

 

Resistance to the combination of sulfadoxine-pyrimethamine which was already present in South America and in South-East Asia is now emerging in East Africa.

 

And since about 2007, evidence of resistance to a newer drug regimen known as ACT (Artemisinin Combination Therapy), has been showing up on the Cambodian-Thai border.  

 

Most recently, the same resistance has been observed in Myanmar, as we learn from this IRIN feature article.

 

MYANMAR: Anti-malarial drug resistance "hotspots" identified

Photo: Wikipedia

Malaria is a leading cause of death in Myanmar

BANGKOK, 19 April 2011 (IRIN) - Health experts had barely finished one project to contain anti-malarial drug resistance along the Thai-Cambodia border when their attention was drawn to Myanmar, where early warning signs suggest a waning influence of the anti-malarial drug Artemisinin.

(Continue . . . )

 

 

Although a far greater problem in the developing world, the CDC’s latest MMWR provides us with a surveillance report on Malaria in the United States for 2009.

Here is a link and an excerpt:

 

Malaria Surveillance --- United States, 2009

Surveillance Summaries

April 22, 2011 / 60(SS03);1-15

CDC received reports of 1,484 cases of malaria, including two transfusion-related cases, three possible congenital cases, one transplant case and four fatal cases, with an onset of symptoms in 2009 among persons in the United States.

 

This number represents an increase of 14% from the 1,298 cases reported for 2008. Plasmodium falciparum, P. vivax, P. malariae, and P. ovale were identified in 46%, 11%, 2%, and 2% of cases, respectively. Thirteen patients were infected by two or more species. The infecting species was unreported or undetermined in 38% of cases.

 

Among the 1,484 cases 1,478 were classified as imported.

 

 

Malaria, like Dengue and Chikungunya, are increasingly becoming concerns in the developed world, including the United States and parts of Europe. 

 

While relatively uncommon, locally acquired cases of Malaria do occur in the United States.  Late last year we saw a suspected case in Jacksonville Florida (see Florida: Locally Acquired Malaria Case Suspected).

 

In 2006, the CDC issued a guide for the investigation of Malaria in the United States, that included the following data on cases between 1957 and 2003.

 

September 8, 2006 / 55(RR13);1-9

Locally Acquired Mosquito-Transmitted Malaria: A Guide for Investigations in the United States

EXCERPT

In the United States, approximately 1,000--1,500 cases of malaria are reported annually to CDC (3). Nearly all of the cases diagnosed in the United States are imported from regions of the world where malaria is endemic. However, a limited number of cases also are acquired through local mosquito borne transmission.

 

From 1957, when the Malaria Branch started conducting malaria surveillance, to 2003, a total of 63 domestic outbreaks have occurred, constituting 156 cases (annual range: 1--32) that resulted from locally acquired mosquitoborne transmission (Figure 1) (4--11).

 

Of the 63 outbreaks, the highest number of cases occurred in California (17 [27%]) (Figure 2). Outbreaks also have occurred in 23 states. Since approximately 1991, a trend has developed in which outbreaks have occurred in more populated areas (e.g., urban and suburban areas). P. vivax has been the predominant species involved (47 [74.6%] of 63), followed by P. falciparum (seven [11.1%] of 47), and P. malariae (five [10.6%] of 47) (Figure 3).

 

 

To finish up our preview of World Malaria Day we have a CDC Grand Rounds video from November of 2010.

 

 

Malaria Eradication: Back to the Future

 

Tune in to Malaria Eradication: Back to the Future, in CDC’s Public Health Grand Rounds monthly series, presented November 18, 2010.

 

You’ll hear four current and former CDC malaria experts discuss review the history of the malaria eradication campaign (1950s-70s), discuss current control successes and challenges, and explore strategies to eliminate, and eventually eradicate, this deadly disease, which caused approximately 860,000 deaths in 2008.

Watch: Malaria Eradication: Back to the Future [CDC | YouTube]

Eastern Equine Encephalitis (EEE)

 

 

# 4741

 

 

Yesterday the local news carried word of the death of an adult female in Hillsborough County (ie. Tampa region), Florida from mosquito borne EEE (Eastern Equine Encephalitis).

 

EEE (Triple `E’) is an often serious, but exceedingly rare illness in humans.  It is one of more than 100 kinds of arbovirus (viruses transmitted by arthropods  e.g., Mosquitoes, sandflies, midges, or ticks).

 

According to the MMWR  (here), between 1999 and 2008 there were a median of seven (range: 3--21) EEE cases (not deaths) reported in the United States each year.

 

In addition to EEE, West Nile virus (WNV), La Crosse virus (LACV), and St. Louis encephalitis virus (SLEV) also circulate at low levels in the United States.

 

 

While of concern, to keep things in perspective, on average 58 people are struck and killed by lightning each year in the United States, and Bee stings account for an additional 40 deaths each year.

 

Which isn’t to minimize EEE or any of the other arboviruses, or to suggest that people not take precautions against mosquitoes, but is simply a reminder that a lot of the diseases we talk about in this column are pretty rare.

 

In recent weeks, Dengue has become a big story here in Florida, but once again, we’re talking a couple of dozen confirmed cases out of a population of 18 million.

 

The actual incidence of Dengue is probably much higher, but as with most viruses, many cases are sub-clinical or asymptomatic and are therefore never diagnosed.  

 

First, the story about the EEE fatality, then a bit of discussion about the way this rare virus makes its way into the human population.

 

First human EEE death confirmed in Hillsborough County

State's first encephalitis death in two years

Updated: Wednesday, 21 Jul 2010, 6:18 AM EDT
 

MyFoxTampaBay.com staff report

TAMPA - Health officials in Hillsborough County have confirmed the first human death this year from Eastern Equine Encephalitis.

 

A woman living in the northern part of the county died July 1, the county health department said, and it is believed that she had other health issues as well.

 

This is the first human death from EEE in the state of Florida since 2008.

 

Four horses in the county have also tested positive for the disease in the last several weeks, according to the health department. Officials say finding the disease in animals means that the likelihood of humans becoming infected increases.

 

Hillsborough County Mosquito Control will be spraying pesticides over much of the county Wednesday morning.

(Continue . . . )

 

While the number of yearly cases is low, the distribution of EEE in the United States far ranging.

 

 

The natural host for the EEE virus are songbirds, which can become infected generally without suffering ill effect.  The virus is spread among these birds by the blood feeding of female mosquitoes (males don’t bite).

 

After an infected mosquito feeds on a bird, the bird becomes infected and the virus begins reproducing. After a few days, and for only a few days, the bird’s bloodstream contains enough virus to infect subsequent mosquitoes that feed on it.

 

Culiseta melanura, which means "curly black hairs", is the species of swamp mosquito that serves as the primary vector for this virus among birds.

 

It, however, isn’t usually attracted to bite humans.

 

So it generally requires a secondary type of mosquito - one that isn’t quite as picky a feeder - such as the Aedes albopictus or  Coquillettidia perturbans  `salt and pepper’ mosquito, to bite an infected bird in order to move it into the equine or human population.

 

Humans and horses don’t develop a high enough viral EEE titer in their bloodstream to pass on the virus if they are subsequently bitten by a mosquito, so they are considered a `dead-end host’.

 

For more on this fascinating topic, I’ve found an absolutely terrific multimedia presentation on arboviruses in Florida.

 

It is a narrated slide show, by Rebecca Shultz, the Arthropod-borne Disease Surveillance Coordinator for the Florida Department of Health, and it covers EEE, SLEV, and West Nile Virus.

 

The presentation runs just over 20 minutes.   The transcript is here.  Click the image below (or this link )to go to the slide show, and turn on your speakers.

 

Highly recommended.

 

 

As the Miami-Dade County Health Department reminds us, to protect yourself from mosquitoes, you should practice the “5 D's”:

• Dusk and Dawn – avoid being outdoors when mosquitoes are very active 
  
• Dress – wear clothing that covers most of your skin 
  
• DEET – repellents containing up to 30 percent DEET (N, N-diethyl-meta-toluamide) are recommended. Other effective mosquito repellents include picaridin, oil of lemon eucalyptus, and IR 3535. Always read label directions for approved usage before your apply a repellent. Some repellents are not suitable for children. 
  
• Drainage – check around your home to remove standing water, where mosquitoes may lay eggs.

 

As long as you observe these simple precautions (and this isn’t just advice for Floridians), you can reduce your (already slight) risk of being infected by any of these mosquito borne illnesses.

 

For those who would like to follow Florida’s surveillance program for arboviruses, weekly reports are available from the Florida Department of Health.

 

Weekly Data for Arbovirus Surveillance