Where is H7N9 in 2018?

I’ve been watching avian influenza A(H7N9) virus cases in humans since they popped onto the radar in 2013 (it was among my first blogs, “H7N9 deaths” [1]).

So I’m confident when I say that 2018 has been a very unusual year for this avian influenza virus.

January is usually H7N9 season in full swing. We see peak spillover activity in China; the highest number of human cases of infection and (usually) illness in humans resulting from contact with infected chickens and other poultry  often via live poultry markets (LPMs) in China. I say often, but for context, there have only been ~1,620 reported human cases and 620 deaths (38% of reported cases are fatal) across 5 years.[2]

“Peak” spillover period may be represented by as few as 30 human cases to more than 200 in January. But in 2018 we’ve seen just 1 case reported this year. 

I’ve hacked the graph below to highlight January in each of the years we’ve known H7N9 to spillover into humans; 2013 to 2018. 2018 is represented by the red, barely visible bar on the right-hand side. Hey Wave 6! Where are you?

Weekly plot of H7N9 human cases from 2013-2018. January is highlighted by yellow arrows. Chinese New Year is indicated with green stars. FAO data from H7N9 update 24JAN2018: http://www.fao.org/ag/againfo/programmes/en/empres/h7n9/situation_update.html [2]

I’ve also highlighted Chinese New Year (CNY; green star). Before, during and after CNY is when the largest human migration on the planet occurs.[9] But despite the many opportunities for enhanced transmission of H7N9, we have to date seen a decline after the CNY. H7N9 is thankfully not an efficiently transmitting Flu virus. It may never be. Or it may be tomorrow.

Assessment of the potential pandemic risk posed by influenza A viruses that are not currently circulating in people. H7N9 is indicated by the red (Yangtze River Delta lineage represented by A/Hong Kong/125/2017) and orange (A/Shanghai/02/2013) data points.[7,8]

So maybe the 2017/18 H7N9 season happened earlier? Nuh. No illnesses reported for December and just a handful from August to November.

Only a few months back we heard about H7N9 being the next big pandemic threat; a multi-billion dollar “sinister” virus that had concerned the Chinese agriculture industry, the World Health Organization, US health authorities and knowledgeable scientists alike [3,4,5,6,7,8]

But in 2018 I have to ask, where has H7N9 gone?


  1. H7N9 deaths
  2. FAO data from H7N9 update 24JAN2018
  3. This Sinister Virus Could Cause the World’s Next Flu Pandemic
  4. CDC Concerned by H7N9 Bird Flu’s Sudden Spread in China
  5. U.N.: H7N9 flu outbreak has cost $6.5 billion so far
  6. World must not miss early signals of any flu pandemic: WHO
  7. Summary of Influenza Risk Assessment Tool (IRAT) Results
  8. Influenza Risk Assessment Tool (IRAT)
  9. Novel influenza A viruses and pandemic threats
  10. Chinese New Year 2017: Largest migration of human beings in the world underway

Views: 6035

6 thoughts on “Where is H7N9 in 2018?”

  1. H7N9 is alive and well! But we are seeing a lot of seasonal flu activity across China (mainly type B and subtype H1pdm09), so that ER, hospitals, outpatients clinics are surely overwhelmed with these cases and a fraction of severe acute respiratory illness likely labeled as seasonal flu even though they are from different origin (avian…). Sometimes there are suggestions that a short-term cross-reactive antibodies could protect or mitigate an infection by heterologous strains, or that there is a certain amount of viral interference by other pathogens such as entero- adeno- or paramyxovirus always circulating when weather conditions are permissive (a very cold season for China this year). The best time for avian flu is perhaps -after- the winter human flu epidemic: in fact, Zhong Nanshan warned Chinese people about the likely new wave next March. But all things about flu are at best well educated guesses: last year Germany experienced a massive wild and domestic poultry epizootic by H5 clade, but this year very few instances of avian flu have been reported. Why? Are the wild acquatic population been primed for H5 and now the remaining populations are partially immune? Perhaps. On the other hand, northern hemisphere is experiencing a severe human influenza season: from Italy, to England, from the US to China, B-Yamagata, H1pdm09 and H3 are everywhere causing havoc in the health infrastructures. Italy is experiencing the worst epidemic since 1998 (at least) with a very high activity especially among children and youngsters (0-4 class of age has an overall incidence of ILI-related illness about 4000 cases per 100,000 inhabitants). Are the unusually cold weather the only culprit? The waning immunity toward B & H1pdm09? The very low vaccine coverage? Or interferences by other viral pathogens?

  2. May be useful to read this? ”CHINESE-ORIGIN H7N9 AVIAN INFLUENZA SPREAD IN POULTRY AND HUMAN EXPOSURE – Qualitative risk assessment update – ASSESSMENT No. 4”, http://www.fao.org/3/i8705en/I8705EN.PDF
    I do not know whether FAO did the right risk assessment regarding the poultry vaccine impact on human H7N9 infections during current season, but perhaps a more science literate reader might…

  3. The answer is quite simple.

    The Chinese vaccinated all chickens in late 2017 and as a result H7N9 is now endemic in ducks. they are working on a vaccine for ducks as we speak.

    The result will be that H7N9 will become endemic in another species,,,,Hope it is not us!

    “In response to bird flu pandemics starting in 2013, officials in China introduced a new vaccine for chickens in September 2017. Recent findings suggest that the vaccine largely worked but detected two new genetic variations of the H7N9 and H7N2 subtypes in unvaccinated ducks

    “Our data show that vaccination of chickens successfully prevented the spread of the H7N9 virus in China,” says Chen. “The fact that human infection has not been detected since February 2018 indicates that consumers of poultry have also been well-protected from H7N9 infection.”

    On a disgusting side note, it was revealed that Chinese consumers eat roughly three billion ducks per year (compared to 14 billion chickens).


Comments are closed.