Three recent Outbreaks Of H5N8
# 9340
For those of us who have been covering avian influenza for a decade or more, the detection of avian H5N8 – a newly emergent influenza virus previously only seen in Korea and far eastern China – in three recent outbreaks in Europe is somewhat reminiscent of the great bird flu diaspora of 2005-2006.
Up until the middle of 2005, the H5N1 virus – which first appeared in China in 1996, and sparked an outbreak in Hong Kong in 1997 – was essentially a southeast Asian problem.
The virus was quashed – temporarily – due to a massive culling in Hong Kong in 1997, but returned in February of 2003, infecting two family members (and likely a third, who died untested) with recent travel history to Fujian Province, China. Another case was retrospectively identified in Beijing (originally diagnosed as SARS) in November of 2003.
In December 2003, the Republic of Korea reported outbreaks in Poultry, and at a zoo in Thailand two tigers and two leopards – fed raw poultry – died of H5N1. Our first clue that felines were susceptible to the virus.
In January of 2004, Vietnam reported poultry and human infections. In rapid succession Japan, Cambodia, Laos, and Hong Kong report poultry and wild bird infections. Thailand reports two human infections as well. Before the end of the year, Indonesian and Malaysia would see the virus arrive as well.
In 2005, after the huge die off of migratory birds at Qinghai Lake, the virus would suddenly take flight – carried by migratory birds – to Russia, the Ukraine, Turkey, and even Kuwait.
By the end 2005, 17 countries had reported infections.
The big geographic expansion came in 2006, when the virus jumped to an additional 39 countries in a single year. Suddenly there were reports in Italy, Bulgaria, Nigeria, Iraq, Iran, Germany, France, The United Kingdom, Egypt . . . .
In most of these regions outbreaks were sporadic, and quickly contained (often at great cost). But in Egypt, the virus became endemic, and remains so to this day, exacting a heavy toll on the poultry industry and causing a small number of human illnesses and deaths every year.
Another half dozen countries were added to the list in 2007, but by 2008, the virus seemed in retreat outside of the bird-flu endemic countries of Indonesia, China, Vietnam, India, Pakistan, Korea, and Egypt.
For the past few years the role of migratory birds in avian flu’s geographic spread appeared to decline.
While the H5N1 threat remains, over the past couple of years, a stealthy (and highly pathogenic to humans) H7N9 has captured out attentions. As it doesn’t sicken birds, it can spread unnoticed, and is often only discovered after humans in contact with infected birds fall ill.
Unlike H5N1, the role of migratory birds in the spread of H7N9 is less than clear.
Last January, the HPAI H5N8 virus appeared on a duck farm in South Korea – and in wild and migratory birds - and over the next couple of months managed to spread to more than 3 dozen farms.
50 day Spread of H5N8 - Map Credit Japan’s MAFF
While highly pathogenic to birds, it hasn’t (yet) shown the ability to infect humans. South Korea did report Dogs With H5N8 Antibodies last spring. As the virus spreads, however, it continues to evolve (see EID Journal: Describing 3 Distinct H5N8 Reassortants In Korea), giving rise to concerns that it could someday pose a greater human health threat.
For now, H5N8 is viewed as primarily a threat to poultry.
Now, across Europe there are concerns that we could see a repeat of the 2006 influx of bird flu. Not only could this cause serious economic losses for the poultry industry, it would allow a novel influenza virus to mingle with – and possibly reassort with – other flu viruses with uncertain results.
While the focus right now is on H5N8, there are several other recently emerged avian flu strains of concern in Asia, any of which could eventually show up in Europe. H7N9 – which has caused the deaths of more than 100 people in China and is exceedingly hard to detect in poultry – is a serious concern.
Others include H5N6 – which killed at least one person in China last spring, H10N8 which infected three people last winter in China, and H5N3 – which was only first reported in China last month.
Today, the World Health Organization is warning that it is likely we will see additional outbreaks of avian flu in European poultry – and while the public health risk is low – the risks are not zero.
Bird flu spread likely, human cases unlikely but possible: WHO
By Tom Miles
GENEVA Tue Nov 18, 2014 9:16am EST
(Reuters) - New cases of bird flu detected in Europe will likely hit other bird populations and may infect a few people, though the virus is highly unlikely to spread in the human population, the World Health Organization (WHO) said on Tuesday.
In March of 2013, in EID Journal: Predicting Hotspots for Influenza Virus Reassortment, we looked at a study that selected East-Central China a one of the top hotspots in the world for the creation of zoonotic influenza viruses. And on Thursday of last week, in EID Journal: Subclinical HPAI In Vaccinated Poultry – China, we looked at the diminishing benefits from China’s poultry vaccination schemes.
Finally, last Sunday, in FAO On The Potential Threat Of HPAI Spread Via Migratory Birds, we looked at concerns over how easily those viruses could spread via interconnected migratory flyways. While we don’t know with certainty how H5N8 has spread to Europe, migratory birds are high on the list of suspects.
While it is possible we could see a repeat of the 2006-2007 expansion of H5N1 with the H5N8 virus, this time around we’ve got much better biosecurity in poultry operations in Europe than we did eight years ago, and considerable experience dealing with outbreaks.
But if the past couple of years has taught us anything, it is that the number of new avian flu subtypes continues to rise, and that the challenges of keeping them at bay are only going to increase with time.
