UN agency warns of possible resurgence of H5N1

Today, the Food and Agriculture Organization of the United Nations recommended heightened readiness and surveillance due to the possibility of a significant resurgence of highly pathogenic H5N1 avian influenza. A mutant strain of the virus is spreading throughout Asia, according to an agency press release.

“The advance appears to be associated with migratory bird movements,” according to Juan Lubroth, Food and Agriculture Organization (FAO) chief veterinary officer. “Migrations help the virus travel over long distances, so H5N1 has in the past 24 months shown up in poultry or wild birds in countries that had been virus-free for several years. Wild birds may introduce the virus, but peoples’ actions in poultry production and marketing spread it.”

Israel, the Palestinian territories, Bulgaria, Romania, Nepal and Mongolia are the latest areas affected by H5N1, according to the press release. More recently, a variant strain of the H5N1 virus surfaced in China and Vietnam. According to FAO officials, the strain could circumvent the defense mechanisms of the existing vaccine.

The H5N1 strain has invaded most of northern and central Vietnam, where the virus is endemic. “Circulation of the virus in Vietnam poses a direct threat to Cambodia, Thailand and Malaysia, as well as endangering the Korean peninsula and Japan further afield,” FAO officials said in the release.

“The general departure from the progressive decline observed between 2004 and 2008 could mean that there will be a flare-up of H5N1 this fall and winter, with people unexpectedly finding the virus in their backyard,” Lubroth said in the release. “The countries where H5N1 is still firmly entrenched — Bangladesh, China, Egypt, India, Indonesia and Vietnam — are likely to face the biggest problems, but no country can consider itself safe. Preparedness and surveillance remain essential. This is no time for complacency. No one can let their guard down with H5N1.”

For the time being, enhanced surveillance would appear to be the best course of action. Unfortunately, activity of this virus is occurring in parts of the world where surveillance is generally less than optimal. If there indeed is a mutant H5N1 virus, we know little or nothing about its infectivity or transmissibility at this point. Watchful waiting is the order of the day. We await further information with great interest.

– Theodore C. Eickhoff, MD

Editor Emeritus of Infectious Disease News

This is not entirely unexpected. It reinforces the need for continuing thorough surveillance of human disease and the need for ongoing pandemic planning by public health authorities and health care facilities around the globe. We recognize that most influenza vaccine around the world is still produced in hen's eggs, and whenever we have a large outbreak of avian influenza, there's a potential threat to egg-based production. This reminds us that there is a need to move the production of influenza vaccines away from the technology of the 1940s and 1950s into contemporary cell-based methods. Western Europe, and indeed the entire Western Hemisphere, including North and South America, are still remote from avian influenza. But given what we learned the last time, it's only a matter of time before these migratory birds and other methods of transmission, including the sale of poultry as well as chicken waste (which is used as fertilizer), are transported in commerce to other countries. We were spared that last time in the Western Hemisphere, but avian influenza could penetrate the Western Hemisphere, so we must maintain rigorous public health surveillance mechanisms.

- William Schaffner, MD

President, National Foundation for Infectious Diseases

Disclosure: Dr. Schaffner reports no relevant financial disclosures.

It is not surprising that new Avian influenza strains emerge, particularly in areas where the virus is widely circulating and where mass vaccination is applied in poultry.

On top of the countries in which H5N1 is still 'firmly entrenched' - Bangladesh, China, Egypt, India, Indonesia and Vietnam - 11 other countries have reported new outbreaks during 2010: Bhutan, Bulgaria, Cambodia, Israel, Japan, South Korea, Laos, Myanmar, Nepal, Romania and Russia. During 2011, new outbreaks were reported, so far, in Cambodia, Israel, Japan, Mongolia, Myanmar and Palestinian Autonomous Territories (PAT). In most countries, the outbreaks were sporadic, involving single or few wild birds (Mongolia, Bulgaria) or likely to be introduced to farms by wild birds. In two countries, the epizootics took considerable dimensions, involving both domestic and wild birds: Japan (71 outbreaks) and South Korea (58 outbreaks). In both countries, the outbreaks started in December 2010, continuing during the first months of 2011, and were eradicated by stamping out without vaccination. No human cases have been recorded in those countries or in other countries where the disease is not endemic. Since January, 49 human cases have been reported to WHO: Bangladesh (n=2), Cambodia (n=8), Egypt (n=32) and Indonesia (n=7). The numbers during parallel periods in previous years were: 88 in 2007, 44 in 2008, 73 in 2009 and 48 in 2010.

It seems that the main concern deserves to be directed at the Asian continent, particularly South and East Asia, with special emphasis upon the emergence of the novel strain in Vietnam and China, apparently not susceptible to control by currently deployed veterinary vaccines. Previous to its emergence, mass vaccinations appeared to be effective in Vietnam. The outbreaks recorded elsewhere in the Balkans (Bulgaria, Romania) and the Middle East (Israel, PAT) seem to have been introduced by wild birds. In the Israel/PAT outbreaks, the disease remained restricted, eradicated by stamping out without vaccination and the causative agent found to be closely related to neighboring Egypt's strains.

The H5N1 AI virus remains one of the influenza viruses with pandemic potential because it continues to circulate in some poultry populations and probably also in populations of wild-water birds; most humans likely have no immunity to it; and it can cause severe disease and death in humans. Its control will require long-term commitments from countries and strong coordination between national and international animal and public health authorities.

- Arnon Shimshony, DVM

Infectious Disease News Editorial Board member

Disclosure: Shimshony reports no relevant financial disclosures.

There is no question that H5N1 is a devastating disease in poultry with vast economic consequences, and that it is a lethal infection in the rare individuals who acquire it - emphasis on rare. While no one can argue with the importance of surveillance, this FAO release seems a bit alarmist. Influenza viruses evolve/mutate; that is what they do. This is not the first sign of change in the virus as evidenced by the various clades of H5N1. The change is apparently enough to render the current veterinary vaccine useless, but there is no evidence for increased transmissibility to or among humans. The outbreaks in poultry were controlled by culling flocks before there was a vaccine, and new vaccines will be prepared. The great fear has been that H5N1 will recombine with a human strain and become more transmissible to humans. While it is always prudent to be prepared for such an event, the fact is that the virus has been circulating widely in populous underdeveloped countries for about 10 years and this has not occurred. There have been less than 600 cases in humans, the vast majority acquired from close contact with back yard flocks and not from regulated commercial poultry farms as found in industrialized countries.

- Donald Kaye, MD

Infectious Disease News Editorial Board member

Disclosure: Kaye reports no relevant financial disclosures.

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