Monday, May 03, 2010

Viruses Blowin’ In The Wind?



# 4544




In January of 2008 I wrote a blog entitled The Virus My Friend, Is Blowin' In The Wind where I cast a skeptical eye upon claims by the Indian Government that the bird flu virus (H5N1) was being blown by the wind across the border from neighboring Bangladesh, and was infecting hapless Indian Poultry.


It wasn’t impossible, of course.


And while dubious, I went so far as to present some evidence that suggested fungi and bacteria do indeed travel thousands of miles, carried aloft by sandstorms in Africa, only to be deposited in the Caribbean.


The following excerpts come from an article published by the Guardian Unlimited in 2004 called It's an Ill Wind.


Tests on airborne dust samples collected in the Caribbean were found to contain infectious spores of the fungus. Scientists suspect the spores had been carried on the wind from Africa, before landing on the ocean surface, sinking and infecting the sea fans. Enough had built up on the ocean floor for the disease to spread. Since then, several outbreaks have been linked to dust clouds.




From air monitoring stations set up in the Virgin Islands, and from samples taken in Africa, Kellogg found that not only were microbes able to travel the thousands of miles from Africa, but that nearly a third of those that survived were known pathogens.


Of course, some types of fungi and bacteria are pretty hearty organisms.  Viral particles are generally far more fragile; susceptible to UV rays, desiccation, and unable to replicate outside of a host.


Fast forward a little over two years, and you guessed it . . . we’ve a study that implies that it is possible for H5N1 (or any Influenza A virus) to be transported across long distances in the air.


First the abstract which appears in Environmental Health Perspectives, then some parting comments.   


A hat tip to Mixin on FluTrackers for posting the link to the PDF.



Ambient Influenza and Avian Influenza Virus during Dust Storm Days and Background Days

Citation: Chen P-S, Tsai FT, Lin CK, Yang C-YY, Chan C-C, Young C-Y, et al. 2010. Ambient Influenza and Avian Influenza Virus during Dust Storm Days and Background Days. Environ Health Perspect :-. doi:10.1289/ehp.0901782


BACKGROUND: The spread of influenza and highly pathogenic avian influenza (H5N1) presents a significant threat to human health. Avian influenza outbreaks in downwind areas of Asian dust storms (ADS) suggest that viruses might be transported by dust storms.


OBJECTIVES: The purpose of our study is to develop a technique to measure ambient influenza and avian influenza virus, and then use this technique to measure concentrations of ambient influenza and avian influenza virus on ADS days and background days. The relationships between ambient influenza and avian influenza virus and air pollutants were also assessed.


METHODS: A high-volume air sampler was used in parallel with a filter cassette to evaluate spiked samples and unspiked samples. Then, air samples were monitored during ADS season using filter cassette coupled with a real-time qPCR assay.


RESULTS: Ambient influenza virus was successfully quantified using the filtration/real-time qPCR method during ADS days and background days. To our knowledge, this is the first report describing the concentration of influenza virus in ambient air. In both the spiked samples and unspiked samples, the concentration of influenza virus sampled using the filter cassette was higher than that using the high-volume sampler. The concentration of ambient influenza A virus was significantly higher during the ADS days than during the background days.


CONCLUSIONS: Our data implied the possibility of long-range transport of influenza virus.




Previously, ambient influenza RNA has been detected in Emergency Room and Asian wet market air sampling studies, although it remains unknown as to whether these low levels of airborne virus were capable of infecting others.


Regardless, the major findings (page 19-20) in this report are fascinating:


In the present study, we successfully quantified ambient influenza A virus during both ADS days and background days.


Our data showed that ambient influenza virus concentration during ADS days was 21 and 31 times higher at the Wan-Li and Shin-Jhuang air monitoring stations, respectively, than that during background days.


In addition, positive samples of A/H5 were all observed during episode days at the Wan-Li station.



If (and it’s still a mighty big `if’) it can be shown that viable influenza viruses can be transported across long distances by the wind, then it might help explain why some areas experience reintroduction of the virus after months or even years.


While I remain skeptical regarding the dispersal of viable viruses in this manner, I’m awfully glad now I didn’t dismiss the idea with a horse laugh two years ago. 


What can I say?   Sometimes I get lucky.