Wednesday, January 08, 2014

H5N1 In Canada: A Matter Of Import


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


# 8142

On a day when Hong Kong has also reported an imported case of bird flu (see HK CHP Statement On Third (likely) Imported H7N9 Case) from China, the news media is scrambling to cover the announcement of a fatal imported case of H5N1 in Canada ((see Alberta Canada Reports Fatal (Imported) H5N1 Infection).


While obviously a concern to public health authorities, the  two most surprising things about this story are that 1) it’s H5N1 avian flu, not the currently more prevalent H7N9s strain and 2) it hadn’t already happened years ago.


As our ability to travel quickly from one continent to the next improves, so does the ability of pathogens to easily cross oceans and borders.  Each year we see hundreds of exotic infections imported into North America or Europe from around the world, and with each importation, their is a low, but non-zero risk of the virus spreading.


None of this is to suggest that today’s report of the importation of H5N1 into Canada heralds a serious bird flu outbreak in North America (the odds are, it won’t). But it does illustrate how easily a virus can wing its way from some far flung area of the world and show up without warning in New York, or London,  Sydney . . . or Alberta, Canada.


In 2003, we saw the SARS virus hop the Pacific on a flight taken by a 78-year-old woman who had stayed at Hong Kong’s Metropole Hotel, where a doctor who had been treating atypical pneumonia cases inadvertently spread the virus to at least a dozen guests.  Two days after returning from Hong Kong the woman fell ill in Toronto, and before that outbreak was contained, 251 people in Canada had been infected, and 44 died (see SARS And Remembrance).


Dengue fever, not seen in my state for 60 years, returned to South Florida in 2009, likely carried by an international traveler (see (see MMWR: Dengue Fever In Key West). Similarly, the West Nile Virus arrived in New York in the late 1990s, and since then quickly spread across the continent (see  CDC West Nile Update) and now infects thousands of people each year.


Last month, the Caribbean saw their first outbreak of the Chikungunya virus (see CDC Update On Chikungunya In The Caribbean), which up until 2005 was only seen in parts of Africa.  Now it spans much of the Indian Ocean, and arrived – almost certainly via an international traveler – to the island of Saint Martin this fall.


Over the years we’ve looked at a number of studies that have modeled the potential epidemic spread of a novel virus via air travel, including:


Science: The Hidden Geometry of Complex, Network-Driven Contagion Phenomena
MIT: Contagion Dynamics Of International Air Travel
Fluing The Friendly Skies (Revisited)


The world’s airlines carry 2.6 billion passengers each year, on more than 17 million flights.  And as the map at the top of this post 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 easily could change planes and continents several times before showing their first signs of illness.


Which is why, last year, the CDC  and Canada’s PHAC issued guidance to  health departments on the testing and isolation of both H7N9 and MERS coronavirus cases (see PHAC: Interim Guidelines For Surveillance Of MERS-COV & H7N9 In Canada), simply because of the real potential of someday seeing imported cases.


And along with these studies, we’ve also looked at research that has found little benefit to airport screening of passengers for possible infection, as the success rate of such screening (including thermal scanners) is relatively poor.


Branswell: Limitations Of Airport Disease Screening

Pathogens At the Gate

Japan: Quarantine At Ports Ineffective Against Pandemic Flu


While attempts will be made to intercept and quarantine potentially contagious travelers during any type of novel flu outbreak, no one should comfort themselves with thoughts that a new, highly contagious flu could be kept out of any country for very long.


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, 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 like the World Health Organization, animal health initiatives like the FAO and OIE , and disease surveillance grows more important with every passing year.


No matter where on this globe you happen to live.

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