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| H7N9 Infections - Credit FAO - Dec 5th Update |
#13,821
Since China's massive nation-wide poultry vaccination campaign, which began during the summer of 2017, we've seen a huge decline in avian flu outbreak reports in poultry - and infections in humans - particularly in Asia, but also around the globe.
H7N9 infections have not been reported in over 6 months, and we've only seen a handful of H5N6 and H9N2 cases reported out of China in the past year.There are always concerns that cases and outbreaks go unreported, particularly from low-resource countries where testing and surveillance is rarely (if ever) done - and from some countries which have a history of not advertising disease outbreaks.
But assuming those are more-or-less constants, there's little doubt that the incidence of avian flu has declined sharply over the past 18 months.How long that happy status 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 nature always bats last.
The World Health Organization has published their latest Summary and Risk assessment, which reports one human infection with the H9N2 virus in Guangdong Province, China (see Guangdong Province Reports Human H9N2 Infection).
First, some excerpts from this relatively brief update, then I'll return with a bit more on the H9N2 virus.
Influenza at the human-animal interface
Summary and assessment, 14 December 2018 to 21 January 2019
New infections 1 : Since the previous update, one human infection with an avian influenza A(H9N2) virus was 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 13 December 2018, 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 13 December 2018, no new laboratory-confirmed human cases of influenza A(H7N9) virus infections were reported to WHO. There have been no publicly available reports from animal health authorities in China of influenza A(H7N9) virus detections in animals in recent months. 3 Overall, the risk assessment has not changed.
Avian influenza A(H9N2) viruses
Since the last update on 13 December 2018, one new laboratory-confirmed human case of influenza A(H9N2) virus infection was reported to WHO. On 3 January 2019, China reported the detection of avian influenza A(H9N2) virus in a 32-year-old woman from Guangdong, with an onset of illness on 19 December 2018. The illness was reportedly mild, but she was hospitalized on 25 December 2018.
The woman did not report exposure to live poultry. During epidemiological investigations, no further cases among family members were reported. Avian influenza A(H9N2) viruses are enzootic in poultry in China.
1For epidemiological and virologic features of human infections with animal influenza viruses not reported in this
assessment, see the yearly report on human cases of influenza at the human -animal interface published in the Weekly
Epidemiological Record. Available at: www.who.int/wer/en/
2 World Health Organization. Case definitions for the four diseases requiring notification in all
circumstances under the International Health Regulations (2005). Available at: www.who.int/ihr/Case_Definitions.pdf
3 Food and Agriculture Organization of the United Nations. H7N9 Situation Update.
http://www.fao.org/ag/againfo/programmes/en/empres/H7N9/situation_update.html
Risk Assessment:
1. What is the likelihood that additional human cases of infection with avian influenza A(H9N2) viruses will occur?
Most human cases are exposed to the A(H9N2) virus through contact with infected poultry or contaminated environments. Human infection tends to result in mild clinical illness. Since the virus continues to be detected in poultry populations, further human cases can be expected.
2. What is the likelihood of human-to-human transmission of avian influenza A(H9N2) viruses?
No case clusters have been reported. Current epidemiological and virologic 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(H9N2) 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.(Continue . . . .)
Despite relatively few documented human infections (see FluTrackers List) - and having a reputation for causing generally less severe human illness than its avian H5 & H7 cousins - LPAI H9N2 is still considered an important player in the avian flu world.
- H9N2 has become widespread - even ubiquitous - among poultry across Europe and the Middle East
- Serological studies suggest human infection is far more common than standard surveillance would have us believe (see J. Infect & Public Health: High Seroprevalence Of Avian Influenza H9 Among Poultry Professionals In Pakistan)
- H9N2 reassorts easily with other viruses, and its internal genes are often found inside many HPAI viruses (including H5N1, H5N6, and H7N9) - (see The Lancet's Poultry carrying H9N2 act as incubators for novel human avian influenza viruses)
- H9N2 viruses continue to accrue evolutionary changes, which include mammalian adaptations, and increased binding to human receptor cells (see PLoS Path: Genetics, Receptor Binding, and Transmissibility Of Avian H9N2).
So, while H9N2 may not be at the top of our pandemic threats list, it is regarded as having at least some pandemic potential (see CDC IRAT SCORE), and several candidate vaccines have been developed over the years.
