An unusual story has appeared in Omani press his week, where worries are expressed that avian flu (or MERS) might be carried in from other regions via the long-lived dust storms that frequent the Middle East during the spring.
While there isn’t a lot of evidence to support the notion that viable avian flu viruses could be carried sucessfully over long distances by dust storms, the idea isn’t completely far-fetched.
Some viruses have been documented capable of traveling significant distances on the wind. As an example, the USDA/APHIS Overview of the FMD Response Plan: The Red Book lists Foot & Mouth Disease (FMD) as being windborne, stating:
FMDV has also been known to spread through windborne transmission, where the virus infects naïve animals located some miles from known infected animals without any history of contact. The distance of windborne transmission over land surfaces depends on the atmospheric conditions and the amount of virus emitted into the air by the infected animals. Sources suggest FMDV may spread to distances of approximately 60 kilometers over land in favorable conditions and potentially even greater distances over water.
Granted, FMDV is more heat tolerant than influenza viruses, but this shows it is possible for viruses to be carried – intact – for hundreds of kilometers. First a link to the Oman story, then I’ll be back with some more research on the long distance propagation of viruses via the wind.
by Rahul Das | February 24, 2015 , 9 : 32 pm GST Muscat: Hospitals in Oman say they are under siege as the changing weather has sparked off health alerts, even as a specialist warned that the walls of dust that barrelled across the Sultanate can transmit a variety of airborne infections, including bird flu.
Dr Thashli Thankachen, physician – internal medicine, Lifeline Medical Centre, said that the dreaded bird flu can drift in a sandstorm from an affected area to another region not previously under an epidemic attack.
"Viruses, bacteria and fungal spores are blown over from one place to another place along with climatic fluctuations increasing the risk of a whole range of infections like respiratory tract infections, conjunctivitis and influenza, in addition to Severe Acute Respiratory Syndrome (SARS), foot and mouth disease, brain fever (Meningitis) etc," he told the Times of Oman on Tuesday.
The warning was issued after hospitals and clinics witnessed a significant increase in footfalls of patients after the temperature dropped by 18° Celsius in the last 72 hours in Muscat.
Long time readers will recall that back in January of 2008 I wrote a blog called The Virus My Friend, Is Blowin' In The Wind where I cast a dubious 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 I went into some of the other types of pathogens (mostly fungi and bacteria) that are known to travel in the wind.
Of course, bacteria and fungi can be pretty hearty organisms. Viral particles are usually far more fragile; more susceptible to UV rays, desiccation, and are further encumbered by being unable to replicate outside of a host.
Fast forward to May of 2010 (see Viruses Blowin’ In The Wind?) and we saw a report in the journal Environmental Health Perspectives, that suggested that it was possible for H5N1 (or any Influenza A virus) to be transported across long (hundreds of kilometers) distances in the air.
Although researchers demonstrated influenza RNA could be detected in ambient air samplings, they didn’t establish that the virus remained viable over long distances.
In December of 2012 we revisited the idea again (see Barnstorming Avian Flu Viruses?) when we looked at a study in the Journal of Infectious Diseases called Genetic data provide evidence for wind-mediated transmission of highly pathogenic avian influenza that found patterns that suggested farm-to-farm spread of the 2003 H7N7 outbreak due to the prevailing wind.
Another study of the same outbreak, Modelling the Wind-Borne Spread of Highly Pathogenic Avian Influenza Virus between Farms (PloS One 2012), found that windborne transmission could have accounted for up to 24% of the transmission over distances up to 25 km.
We have also seen studies indicating that the H5N1 virus can – under the right environmental conditions – remain viable for hours or even days in the environment (see EID Journal: Persistence Of H5N1 In Soil and H5N1: Hiding In Plain Sight)
So, the science is far being a slam-dunk one way or the other on the issue. Short-distance carriage (20-30km) seems plausible, and while I’m somewhat skeptical, longer-distance travel doesn’t seem to have been completely ruled out.
But it would probably take ideal environmental conditions - and a coalescing of a lot of unlikely factors – for an infectious dose of H5N1 to successfully migrate across several hundred kilometers of desert on the back of an Arabian dust storm.