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?

References…

  1. H7N9 deaths
    https://virologydownunder.blogspot.com.au/2013/07/h7n9-deaths.html
  2. FAO data from H7N9 update 24JAN2018
    http://www.fao.org/ag/againfo/programmes/en/empres/h7n9/situation_update.html
  3. This Sinister Virus Could Cause the World’s Next Flu Pandemic
    https://www.bloomberg.com/news/articles/2017-09-28/bird-flu-mutation-in-china-stokes-pandemic-worry-quicktake-q-a
  4. CDC Concerned by H7N9 Bird Flu’s Sudden Spread in China
    https://www.nbcnews.com/health/health-news/cdc-concerned-h7n9-bird-flu-s-sudden-spread-china-n728946
  5. U.N.: H7N9 flu outbreak has cost $6.5 billion so far
    http://vitals.nbcnews.com/_news/2013/05/21/18402343-un-h7n9-flu-outbreak-has-cost-65-billion-so-far?lite
  6. World must not miss early signals of any flu pandemic: WHO
    https://www.reuters.com/article/us-health-birdflu-who/world-must-not-miss-early-signals-of-any-flu-pandemic-who-idUSKBN157166
  7. Summary of Influenza Risk Assessment Tool (IRAT) Results
    https://www.cdc.gov/flu/pandemic-resources/monitoring/irat-virus-summaries.htm
  8. Influenza Risk Assessment Tool (IRAT)
    https://www.cdc.gov/flu/pandemic-resources/national-strategy/risk-assessment.htm
  9. Novel influenza A viruses and pandemic threats
    http://www.thelancet.com/journals/lancet/article/PIIS0140-67361731274-6/fulltext
  10. Chinese New Year 2017: Largest migration of human beings in the world underway
    http://www.independent.co.uk/news/world/asia/chinese-new-year-2017-fire-rooster-largest-migration-a7546326.html

1 thought 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 2.3.4.4, 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?

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