Monday, May 23, 2016

WHO Avian Flu Risk Assessment - May 2016

4 Epidemic Waves Of H7N9 - Credit WHO


The World Health Organization has published their monthly Influenza at the Human-Animal Interface risk assessment (dated May 9th, but just posted) which provides details on three different types of human avian flu (H5N6, H7N9, and H9N2) infections reported during the last reporting month. 

Influenza at the human-animal interface

Summary and assessment, 5 April to 9 May 2016

New infections: Since the previous update, new human infections with A(H5N6), A(H7N9) and A(H9N2) viruses were reported.

Risk assessment outcome: The overall public health risk from currently known influenza viruses at the human-animal interface has not changed. Since animals are reservoirs for influenza, further human infections with viruses of animal origin can be expected but the likelihood of sustained human-to-human transmission remains low.

Reporting: All human infections caused by a new influenza subtype are reportable under the International Health Regulations (IHR, 2005). 2 This includes any animal and non-circulating seasonal viruses. Information from these notifications will continue to inform risk assessments for influenza at the human-animal interface.

Although H7N9 remains the most active of the avian flu viruses this winter, as the epi curve chart at the top of this post shows, overall reports of H7N9 infection have declined this year.

Whether this is due to a change in the virus, the environment, or a change in reporting and surveillance is hard to tell. 

Todays report lists 17 new cases (previously reported in this blog) and details one additional cluster, albeit from last February and March:

The cluster included an 85-year-old female from Zhejiang Province. She had onset of symptoms on 1 March and passed away on 8 March. She had been admitted to the same hospital and shared the ward with a confirmed case between 22 and 23 February. She was not exposed to live poultry or live poultry market, according to her relatives.

The confirmed case admitted to the same ward was a 29-year-old male from Zhejiang Province who developed symptoms on 15 February. He had exposure to a live poultry market and a household contact that was also a confirmed case. The household contact (from Fujian Province) developed symptoms on 4 February and had exposure to a live poultry market.

Human to human transmission between the 29-year-old male and the 85-year-old female is likely considering the virological information obtained thus far. For more details on the cluster, see the Disease Outbreak News.

On the ascendant the past few months has been the H5N6 virus, which up until last December, had only infected 5 people in the previous year and a half.  Since then, the number of cases has almost tripled (n=14).

Over the past couple of months we've looked at the continuing evolution of H5N6 viruses (see Novel Reassortant H5N6 Viruses In Humans, Guangdong China and J. Virology: H5N6 Receptor Cell Binding & Transmission In Ferrets)

Today's WHO assessment notes not only the increase in human infections, but the ongoing evolution of the virus as well.

Avian influenza A(H5) viruses

Current situation:

Three new human A(H5N6) virus infections were notified to WHO in this reporting period (Table 1). These are the first human cases of A(H5N6) virus infection reported from Anhui and Hubei provinces. All three cases had exposure to live poultry or live poultry markets. 

A total of 14 laboratory-confirmed cases of human infection with avian influenza A(H5N6) virus, including six deaths, have been detected in China since 2014. In the past four months, twice as many cases have been reported since the first case was detected in 2014.

According to the animal health authorities in China 3,4 , influenza A(H5N6) viruses have been detected in poultry in recent months in many provinces in the country, including those reporting human cases. Recent publications indicate ongoing evolution of avian influenza A(H5N6) viruses through reassortment with other avian influenza viruses resulting in viruses with different internal genes. 5,6

To date, no changes in transmissibility in humans have been detected as a result of these reassortant 1viruses. Surveillance is continuing in both human and animal populations to monitor for further virus evolution. All recent avian influenza A(H5N6) viruses that have been tested remain susceptible to the neuraminidase inhibitor class of antiviral drugs.

And lastly, the report fleshes out a bare bones report we picked up earlier this month (see Egypt: FAO Reports Human LPAI H9 Infection).

Avian influenza A(H9) viruses
Current situation:

One human infection with avian influenza A(H9) virus was reported from Egypt. The case is a 18-month-old male from Cairo Governorate who developed influenza-like illness on 10 April 2016. On20 April 2016, a sample from this patient tested positive for an influenza A(H9) virus. The patient is reportedly in good condition and the epidemiological investigation revealed the case had exposure to live poultry at a market in the two weeks prior to onset of illness. While infection with influenza A(H9N2) is likely in this case, laboratory confirmation of the neuraminidase type is anticipated.

A total of 28 laboratory-confirmed, non-fatal cases of human infection with avian influenza A(H9N2) viruses have been detected globally in the past. In most human cases, the associated disease symptoms have been mild and there has been no evidence of human-to-human transmission.

Influenza A(H9N2) viruses are enzootic in poultry populations in parts of Africa, Asia and the Middle East. The majority of viruses that have been sequenced belong to the A/quail/Hong Kong/G1/97 (G1), A/chicken/Beijing/1/94 (Y280/G9), or Eurasian clades.

While H9N2 is generally viewed as a lesser human health threat, we've followed its continual evolution as well (see Genomic Characteristics Of 2 A(H9N2) Virus Isolates From Humans In Anhui Province - 2015), and like H5N6, case reports have increased over the past year.

The report closes with the WHO's overall recommendations, which stresses the need for global surveillance, continued vigilance and the importance of rapid and accurate reporting.