Avian Flu Diary: WHO: Influenza at the Human-Animal Interface (Oct 2nd

China's H5N6 Problem - 31 Cases in 2021

#16,444

The World Health Organization has published its latest Influenza the Human-Animal Interface report, covering cases reported globally between Oct 2nd and Dec 13th, 2021, which they summarize as:

Since the previous update on 1 October 2021, nine human cases of infection with avian influenza A(H5N6) viruses, four human cases of infection with avian influenza A(H9N2) viruses and one human case of infection with an influenza A(H1N2) variant virus were reported officially. Three human cases of infection with influenza A(H1N1) variant viruses, one human case of infection with an influenza A(H1N2) variant virus, one human case with influenza A(H1Nx) variant virus and one human case of infection with an influenza A(H3N2) variant virus were also detected.

Surveillance and reporting of human infections with novel flu viruses remains spotty, and often delayed, around the world, and so many cases likely go undetected. The WHO continues to urge member nations to reports cases promptly.

Of greatest concern currently are the growing number of H5N6 cases reported by China, although we've seen no indication that this virus has evolved to the point where it can transmit efficiently from human-to-human.

Influenza at the human-animal interface

Summary and assessment, from 2 October 2021 to 13 December 20211

• New infections2 : Since the previous update on 1 October 2021, nine human cases of infection with avian influenza A(H5N6) viruses, four human cases of infection with avian influenza A(H9N2) viruses and one human case of infection with an influenza A(H1N2) variant virus were reported officially. Three human cases of infection with influenza A(H1N1) variant viruses, one human case of infection with an influenza A(H1N2) variant virus, one human case with influenza A(H1Nx) variant virus and one human case of infection with an influenza A(H3N2) variant virus were also detected.

• 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. Human infections with viruses of animal origin are expected at the human-animal interface wherever these viruses circulate in animals.

• IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005).3 This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin 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 A(H5) viruses

Since the last risk assessment on 1 October August 2021, nine cases of influenza A(H5N6) virus infection were reported from China to WHO. Table 1. Human cases of influenza A(H5N6) reported to WHO from China from 1 October 2021 to 7 December 2021.

The fatal case (the 54-year-old woman from Sichuan) reportedly had underlying conditions. No clusters of cases were reported associated with these cases. Environmental samples collected from backyard poultry or live poultry markets linked to some of these cases have tested positive for Influenza A(H5) by the local public health institutions. 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.

Risk Assessment:

1. What is the likelihood that additional human cases of infection with avian influenza A(H5) viruses will occur? The overall risk assessment is unchanged. Most human cases were sporadic infections exposed to A(H5) viruses through contact with infected poultry or contaminated environments, including live poultry markets. Since the viruses continue to be detected in animals and related environments, further human cases can be expected. The detection of influenza A(H5) virus in nasopharyngeal/oropharyngeal samples collected from individuals in close contact with infected poultry or other birds, whether the individuals are symptomatic or not, is not unexpected. Good quality serological investigations can be useful in differentiating infection in humans from localized contamination and allow for better assessment of the associated risk.

2. What is the likelihood of human-to-human transmission of avian influenza A(H5) viruses? Even though small clusters of A(H5) virus infections have been reported previously including those involving health care workers, current epidemiological and virological evidence suggests that influenza A(H5) viruses have not acquired the ability of sustained transmission among humans, thus the likelihood is low.

3. What is the risk of international spread of avian influenza A(H5) viruses by travellers? 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 evidence suggests these viruses have not acquired the ability to transmit easily among humans.