In the shadow of the coronavirus: China records bird flu outbreak

Press/Media: Expert Comment


Could you talk about the history of Bird Flu?

 PD- Bird flu is the more recent colloquial name for avian influenza – usually used for strains of virus that have jumped into humans. As an avian disease, it has quite a long history – certainly as far back as the 19th Century when outbreaks of “fowl plague” were noted. The oldest isolate of influenza A virus is (or at least was – it may have been lost over the years by contamination in the laboratory with another strain of the virus) actually an avian virus. Known then as “fowl plague”, the virus was isolated in 1902 in Italy. The first human strain of the virus wasn’t isolated until 1933, and it was another twenty years or so after that before people realised that “Fowl Plague Virus” was actually the same type of virus as that which caused human influenza. For the next four decades, avian influenza was largely viewed as just a problem for poultry; a few infections of human by an avian strain of flu were recorded, but these were largely mild and self-limiting, often presenting as conjunctivitis only. This all changed in 1997 when a small but serious outbreak of human infection with an avian H5N1 strain was detected in Hong Kong. Only 18 people were infected, but 6 died, an alarming level of mortality for a type of virus known to cause global pandemics every few decades in which upwards of a third of the world’s population could expect to be infected. Fortunately, although the H5N1 virusPD - could jump from poultry to people, it couldn’t then transmit from person to person. The outbreak was successfully controlled by eradicating the source of the virus (within Hong Kong) by depopulating all the local live bird markets. Unfortunately, the virus remained in wild birds on mainland China and it reappeared in 2003, again in Hong Kong (where once again it was successfully controlled), but also elsewhere in S.E. Asia (where it wasn’t controlled). Over the next decade or so, the H5N1 virus and its descendants (so called H5NX strains) have spread around much of the world. Between 2003 and the present, the official figures from the WHO confirm over 800 human infections and  455 deaths, reinforcing the potential threat of the virus. However, the virus never (or at least not so far) evolved to be human-transmissible, thus sparing the world a potentially devastating pandemic. Human cases of H5n1 infection peaked in 2006 and (barring one spike in 2015 in Egypt) have dwindled to nothing in 2018 and only a single case in 2019. The reasons for this gradual reduction in the numbers of human infections are probably as much to do with the circumstances of how the virus has evolved in wild birds as any intervention measures; the virus also remains a deadly threat to poultry, as the 2015 H5N2 outbreak in the US showed. Descendants of H5N1, such as the H5N6 variant, still pose something of a threat to humans. In the last 5 years or so, around two dozen people have been confirmed to have been infected with this strain and seven have died.

2- Could you talk about the recent outbreak the Bird flu in China?

PD – I’m not sure which outbreak you’re referring to. SL has this to say:

Recent outbreak of Bird Flu in China

WHO page


Between 2015 and 2019 there were only 6 reported human cases of H5N1 in China and one death, and there have been no reported human cases of H5N1 in 2020 as yet (data up to 20 Jan 2020).


In the human-animal risk assessment for avian influenza between. November - January 2020 the WHO says “Risk assessment: The overall public health risk from currently known influenza viruses at the human-animal interface has not changed, and the likelihood of sustained human-to-human transmission of these viruses remains low. Further human infections with viruses of animal origin are expected.” 


For H7N9, there have been 5 or 6 waves of outbreaks since 2013; the first 4 waves were of low pathogenic Avian influenza, but in wave 5 the low pathogenic strain acquired the multi-basic cleavage site in the hemaggluttinin viral surface protein which resulted in the spread of highly pathogenic avian influenza in poultry.  Since 2013 there have been over 1,500 confirmed human infections, but only 33 of them were with the highly pathogenic H7N9 form.  When the highly pathogenic form of the virus emerged, the Chinese authorities began an intensive vaccination program for domestic birds to control the H5 and H7 viruses, and consequently only a few infections were detected in wave 6. 


However, although both the H5 and H7 viruses were seeming to be coming under control in China (although outbreaks in domestic birds have occurred), the H5 viruses also entered the domestic duck populations and after reassortment with other circulating low pathogenic forms, have been transported via wild birds to other countries in Asia, Europe and North America [H5N8 Science paper ref].  One sub-strain of highly pathogenic H5 viruses, the H5NX, reassort frequently and acquire different subtypes of the neuraminidase surface protein.  This includes the N2, N6, N5, and N8 making H5N2, H5N6, H5N5 and H5N8 viruses.  In fact there are two H5N6 strains, one of them (the Asian lineage H5N6), which has caused around 30 confirmed cases in humans, with 15 of them fatal. 


3- Is H5N6 a new threat in Asia? Why?

 PD- I wouldn’t say it is a new threat – more an evolution of the H5 threat that we’ve lived with for the last 20 years.

SL - In 2020, two new outbreaks of highly pathogenic H5 viruses have been reported in domestic birds, one of H5N6 in Vietnam, and one of H5N1 in China.  Although this is not good news, it is not unexpected since HPAI H5 has not been eradicated from these regions (and infant is considered endemic).  Meanwhile, HPAI H5N8 has also reached Europe again (Winter 2019/2020) and there are again detections in wild birds with some outbreaks in poultry.  

4- In your opinion, what are the main challenges in relation to Bird flu in China?

PD – this is a huge topic. The primary problem is that the reservoir of the virus is the wild bird population, which cannot be directly controlled. Another big problem is biosecurity – preventing the influx of influenza viruses from the wild bird population into domestic poultry. Experience says this is not easy even in large commercial holdings where birds are kept indoors in barns with routine disinfection protocols in place. In a country where there are still large numbers of relatively small poultry farms with low biosecurity, feeding into live bird markets where humans and poultry come into daily contact, it is even harder to manage. It should be noted however, that (as Sam mentions above), the recent H5/H7 poultry vaccination programme put in place by the Chinese government has been very successful indeed at controlling the H7N9 virus. This is a valuable lesson that many countries could learn from.

5- In your opinion, what is the reason for the increase in highly pathogenic Bird flu?

 The numbers of recorded HPAI outbreaks have increased in the last 60 + years.  The increase is likely to be multifactorial. Better reporting will be partly behind this. The happenstance of H5N1 appearing from wild birds and (unlike any previously known HPAI virus), managing to survive and transmit over continental distances in the wild bird population is undoubtedly another factor. The growth in the global poultry industry will also have played a part.

6- The article "Quantifying predictors for the spatial diffusion of avian influenza virus in China" ( highlights that highlighted that the economic-agricultural predictors, especially the poultry population density and the number of farm product markets, are the key determinants of spatial diffusion of AIV in China; high human density and freight transportation are also important predictors of high rates of viral transmission; Climate features (e.g. temperature) were correlated to the viral invasion in the destination to some degree; while little or no impacts were found from natural environment factors (such as surface water coverage). Do you agree? Why?

PD – I would say that just because this study didn’t detect a major effect from things like surface water coverage doesn’t mean that this doesn’t play a role in some circumstances – plenty of other epidemiological data indicate that surface water, which attracts wild birds, can be facilitating factor for spread of AI into poultry.

7- What we can expect in relation to the Bird flu in China in the coming weeks and months?

This is very difficult to predict – hopefully a quiet period! The Chinese do not need any more viral outbreaks to contend with.

8- Can we say that Bird flu in China is the next big risk to global security? Why?

 I would say bird flu remains a serious risk, but is not THE next big risk. Clearly SARS-CoV-2 is the current big risk and I’m not sure many people predicted that. Scientists have been studying viruses for over a century now and one of the lessons we keep being reminded of is that there’s always a surprise around the corner. Hanta, Ebola, Zika, SARS, Schmallenberg, an H1N1 influenza pandemic when we already had H1N1, just to name a few examples…


Period15 Mar 2020

Media contributions


Media contributions

  • TitleIn the shadow of the coronavirus: China records bird flu outbreak
    Degree of recognitionInternational
    Media name/outletBrazilian Society of Tropical Medicine (BSTM)
    Media typePrint
    Country/TerritoryUnited Kingdom
    PersonsPaul Digard