Major Global Migratory Flyways – Credit FAO
Although currently a far greater concern to poultry producers than to public health, we’ve been watching the first incursion of HPAI (Highly Pathogenic Avian Influenza) Eurasian H5 viruses into North America over the past few months, as has the CDC.
Until November of last year, HPAI H5N8 had been essentially a threat only to East Asia.
It first appeared in Korea in January of 2014, was carried to Japan by migratory birds that spring (and again last fall), and had been reported in North Eastern China. While it recently has produced a massive outbreak in Taiwan - it had not strayed outside of the far northern half of the East Asian Flyway.
At least, not until early November when it abruptly showed up at a German poultry farm (see Germany Reports H5N8 Outbreak in Turkeys), which was quickly followed by reports in the Netherlands, the UK, and eventually even Italy and (this week) Hungary.
Remarkably, H5N8 had travelled farther in a matter of a few months than its H5N1 cousin had managed to do over several years. A history we looked at three months ago in H5N8: A Case Of Deja Flu?
It was only few weeks later that British Columbia reported an outbreak of HPAI H5N2 (see Fraser Valley B.C. Culling Poultry After Detecting H5 Avian Flu), followed two weeks later by the announcement from OIE/APHIS: HPAI H5N8 & H5N2 Detected In Washington State Wild Birds.
H5N8 had done in less than a year what H5N1 has yet to do since it re-emerged in 2003; it crossed oceans and got a foothold in North America.
And once here, it has managed to successfully reassort with North American (NA) avian influenza viruses, producing new, highly pathogenic subtypes. In short order wild and migratory birds in six western states (Washington, California, Oregon, Idaho, Utah & Nevada) were discovered to be carrying these viruses (see Oregon Quarantines Another Backyard Flock Over HPAI).
The USDA maintains an Avian Flu Information page where they post the latest news:
Last Modified: Feb 25, 2015
A Threat to U.S. Poultry
Worldwide, there are many strains of avian influenza (AI) virus that can cause varying degrees of clinical illness in poultry. AI viruses can infect chickens, turkeys, pheasants, quail, ducks, geese and guinea fowl, as well as a wide variety of other birds. Migratory waterfowl have proved to be a natural reservoir for the less infectious strains of the disease.
AI viruses can be classified as highly pathogenic (HPAI) or low pathogenic (LPAI) strains based on the severity of the illness they cause. HPAI is an extremely infectious and fatal form of the disease that, once established, can spread rapidly from flock to flock and has also been known to affect humans. LPAI typically causes only minor illness, poses no risk to human health, and sometimes manifests no clinical signs. However, some LPAI virus strains are capable of mutating under field conditions into HPAI viruses.
USDA’s Animal and Plant Health Inspection Service (APHIS) works to keep HPAI from becoming established in the U.S. poultry population.
The good news is, thus far, we’ve seen no evidence of a serious threat to human health from these viruses, but the CDC remains cautious and has issued specific guidance documents (see CDC Interim Guidance For Testing For Novel Flu & CDC Interim Guidance On Antiviral Chemoprophylaxis For Persons With Exposure To Avian Flu).
With Avian flu on the move again, and with serious outbreaks involving humans both in China and Egypt, the bird flu threat is once again making public health headlines (see WHO Warns On Evolving Influenza Threat). Late this week the CDC posted the following statement on H5 viruses in North American birds.
Washington and Nevada. No human infections with these viruses have been reported to date.
Avian influenza (Bird flu) is a viral disease of birds. Migratory waterfowl and shore birds may carry avian influenza viruses that do not usually make them sick. Avian influenza viruses can be classified as either “low pathogenic” avian influenza viruses or “highly pathogenic” avian influenza viruses (HPAI), based on molecular characteristics and the ability of the virus to cause disease in birds. HPAI viruses can cause severe illness and death in birds, particularly in domestic poultry.
In general human infections with avian influenza viruses are rare and most often occur after people are in direct or close contact with an infected bird. Illnesses in humans from avian influenza virus infections have ranged in severity from mild to severe.
While no human infections with these HPAI H5N8, H5N2, or this new H5N1 virus have been reported worldwide, similar viruses (like Asian-origin H5N1, for example) have infected people in the past. The H5N1 virus recently isolated from a U.S. wild bird is a new mixed-origin virus (a reassortant) that is genetically different from the Asian-origin avian H5N1 viruses that have caused human infections with high mortality.
CDC is communicating and coordinating with state health departments on appropriate human health measures and is working with animal health colleagues to evaluate and minimize public health risk. The risk to people from these HPAI H5 infections in U.S. birds and poultry is believed to be low at this time because these viruses do not normally infect humans easily, and even if a person is infected, the viruses do not spread easily to other people. People in contact with known infected or possibly infected birds should take precautions to protect against infection. In addition, CDC has developed testing and influenza antiviral prophylaxis guidance for persons exposed to birds possibly infected with HPAI H5 viruses.
Because avian influenza A viruses have the potential to change and gain the ability to spread easily among people, monitoring for human infection and person-to-person transmission is extremely important for public health.
CDC continues to monitor this situation to minimize the risk to people and will provided updated information as it becomes available.
The U.S. Department of Interior (DOI) and the USDA are the lead federal agencies for outbreak investigation and control in wild birds and the USDA APHIS is the lead agency for such activities in domestic birds. The latest information on avian influenza findings in the Pacific Flyway is available on USDA’s website.