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| A Dearth Of H7N9 Cases Since 2017 |
#14,008
China's massive, nation-wide poultry H5+H7 vaccination campaign, which began in 2017, has resulted in a huge decline in avian flu outbreak reports - both in poultry, and in humans - across Asia over the past 18 months.
While we've seen a handful of H5N6 outbreaks, and human infections, over the past 8 months the suppression of the biggest perceived pandemic threat - H7N9 - has been nearly complete for the past year.On April 5th that drought in H7N9 cases ended with an announcement from Hong Kong's CHP (see Gansu Reports China's 1st Human H7N9 Case Of 2019). This followed closely on the heels of a March 25th report: China MOA: 1st Outbreak Of H7N9 (in Birds) Since Summer of 2018.
While there are always concerns that cases and outbreaks go unreported, particularly from low-resource countries where testing and surveillance is rarely (if ever) done - there is little doubt that the avian flu threat has receded - at least temporarily.
How long this welcomed lull will continue is anyone's guess, but influenza virus evolution continues around the world on numerous fronts - often hidden from view - and history tells us that droughts always end.The World Health Organization has published their latest Summary and Risk assessment, which reports the human H7N9 case previously mentioned, and an H9N2 infection we looked at in late March (see Macao MOH Notified Of H9N2 Case In Jiangsu Province).
A few excerpts from this relatively brief update, then I'll return with a postscript.
Influenza at the human-animal interface
Summary and assessment, 13 February to 9 April 2019
New infections 1 : Since the previous update on 12 February 2019, new human infections with avian influenza A(H7N9) and A(H9N2) viruses were reported.
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.
IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005). 2 This includes any influenza A virus that has demonstrated the capacity to infect a human and its heamagglutinin gene (or protein) is not a mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human population. Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.
Avian Influenza Viruses
Current situation:
Avian influenza A(H5) viruses
Since the last update on 12 February 2019, no new laboratory-confirmed human cases of influenza A(H5) virus infections were reported to WHO. According to reports received by the World Organisation for Animal Health (OIE), various influenza A(H5) subtypes continue to be detected in birds in Africa, Europe and Asia. Overall, the risk assessment has not changed.
Avian influenza A(H7N9) viruses
Since the last update on 12 February 2019, one new laboratory-confirmed human case of influenza A(H7N9) virus infection was reported to WHO by China. An 82-year-old male developed illness on 18 March 2019 and was hospitalized on 31 March 2019 with severe pneumonia. The case was reported from Gansu province, but potential exposure reportedly occurred in the Inner Mongolia region of China.
No further human cases were reported among his close contacts. Additional information on the potential exposure and the virus from the case are anticipated.
Since 2013, a total of 1568 laboratory-confirmed cases of human infection with avian influenza A(H7N9) viruses, have been reported to WHO (Figure 1). There have been no publicly available reports from animal health authorities in China of detections of influenza A(H7N9) virus in animals this year, except for one report of an outbreak in domesticated birds in Liaoning Province 3 .
Risk Assessment:
1. What is the likelihood that additional human cases of infection with avian influenza A(H7N9) viruses will occur?
Most human cases are exposed to the A(H7N9) virus through contact with infected poultry or contaminated environments, including live poultry markets. Wherever the virus circulates in animals, further human cases can be expected.
2. What is the likelihood of human-to-human transmission of avian influenza A(H7N9) viruses?
Even though small clusters of cases have been reported, including those involving healthcare workers, currently available epidemiological and virological evidence suggests that this virus has not acquired the ability of sustained transmission among humans, thus the likelihood is low.
3. What is the likelihood of international spread of avian influenza A(H7N9) virus by travelers?
Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. If this were to occur, further community level spread is considered unlikely as this virus has not acquired the ability to transmit easily among humans.
Avian influenza A(H9N2) viruses
Since the last update on 12 February 2019, one new laboratory-confirmed human case of influenza A(H9N2) virus infection was reported to WHO from China.
A 9-year-old male from Jiangsu province developed illness on 15 March 2019 and was hospitalized the next day with severe pneumonia. The case reportedly had exposure to a live poultry market. No further human cases were reported among his close contacts.
Characterization of the virus from this case has been completed at the WHO Collaborating Centre in Beijing, China.(Continue . . . . )
The remarkable reduction in H5 and H7 avian flu activity in China following their massive poultry vaccination program has exceeded all expectations, and its effects could persist for some time.
While this may have provided us a temporary reprieve against the biggest avian threat - H7N9 - China continues to be a hotbed for other novel flu threats including avian, swine and canine varieties.And China isn't the only place capable of launching a novel flu pandemic. We are rapidly coming up on the 10th anniversary of the last (swine-origin H1N1) pandemic, which sprang forth from North American pigs.
A reminder that while avian flu activity has dropped globally over the past year - viruses have survived for millions of eons based on their ability to evolve and evade acquired herd immunity - and that modern vaccines and antivirals used to combat them generally have a limited lifespan.Which means while we enjoy this lull, we should also be using this respite to prepare for the next big global health crisis. While the following quote is more than a dozen years old, it is just as true today as it was in 2006:
“Everything you say in advance of a pandemic seems alarmist. Anything you’ve done after it starts is inadequate."- Michael Leavitt, Former Secretary of HHS
