#16,683
After several weeks of hearing little or nothing about China's year-long surge in human H5N6 infections, we've our second report in just 4 days. Reporting from China is often erratic, and frequently belated, making it difficult to know how accurate of a picture we really have of their avian flu situation.
Today's case is the 12th of 2022, and follows more than 3 dozen cases reported in 2021.
Between 2014 and late 2020, China has reported an average of just 4-5 cases a year, and had seen a 3 year decline in cases following the introduction of a new H5+H7 poultry vaccine in 2017.
While we only rarely see reports of H5N6 in Chinese poultry - most human infections are linked to poultry exposure - suggesting the virus may be transmitting stealthily in poultry due to an increasingly ineffective vaccine.
First, today's report from Hong Kong's CHP, followed by a look at a new study - published in the EID Journal - that looks at the recent evolution of HPAI H5N6 in China.
CHP closely monitors human case of avian influenza A(H5N6) in Mainland
The Centre for Health Protection (CHP) of the Department of Health is today (April 9) closely monitoring a human case of avian influenza A(H5N6) in the Mainland, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.
The case involves a 53-year-old female living in Zhenjiang City in Jiangsu Province, who had visited a live poultry market before onset. She developed symptoms on March 24 and was admitted for treatment on March 26. She is in critical condition.
From 2014 to date, 76 human cases of avian influenza A(H5N6) have been reported by Mainland health authorities.
"All novel influenza A infections, including H5N6, are notifiable infectious diseases in Hong Kong," a spokesman for the CHP said.
Travellers to the Mainland or other affected areas must avoid visiting wet markets, live poultry markets or farms. They should be alert to the presence of backyard poultry when visiting relatives and friends. They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings. They should strictly observe personal and hand hygiene when visiting any place with live poultry.
Travellers returning from affected areas should consult a doctor promptly if symptoms develop, and inform the doctor of their travel history for prompt diagnosis and treatment of potential diseases. It is essential to tell the doctor if they have seen any live poultry during travel, which may imply possible exposure to contaminated environments. This will enable the doctor to assess the possibility of avian influenza and arrange necessary investigations and appropriate treatment in a timely manner.
While local surveillance, prevention and control measures are in place, the CHP will remain vigilant and work closely with the World Health Organization and relevant health authorities to monitor the latest developments.
The public should maintain strict personal, hand, food and environmental hygiene and take heed of the advice below when handling poultry:
- Avoid touching poultry, birds, animals or their droppings;
- When buying live chickens, do not touch them and their droppings. Do not blow at their bottoms. Wash eggs with detergent if soiled with faecal matter and cook and consume the eggs immediately. Always wash hands thoroughly with soap and water after handling chickens and eggs;
- Eggs should be cooked well until the white and yolk become firm. Do not eat raw eggs or dip cooked food into any sauce with raw eggs. Poultry should be cooked thoroughly. If there is pinkish juice running from the cooked poultry or the middle part of its bone is still red, the poultry should be cooked again until fully done;
- Wash hands frequently, especially before touching the mouth, nose or eyes, before handling food or eating, and after going to the toilet, touching public installations or equipment such as escalator handrails, elevator control panels or door knobs, or when hands are dirtied by respiratory secretions after coughing or sneezing; and
- Wear a mask if fever or respiratory symptoms develop, when going to a hospital or clinic, or while taking care of patients with fever or respiratory symptoms.
The public may visit the CHP's pages for more information: the avian influenza page, the weekly Avian Influenza Report, global statistics and affected areas of avian influenza, the Facebook Page and the YouTube Channel.
Ends/Saturday, April 9, 2022
Issued at HKT 18:00
In addition to seeing a marked increase in human H5N6 infections over the past 16 months, we've also seen a number of studies coming out of China describing evolutionary changes - and potential signs of mammalian adaptation - in the virus.
China CCDC Weekly: Genetic Characterization of Two Human A (H5N6) Viruses — Guangxi , China, 2021
CCDC Weekly: Outbreak Report - Five Independent Cases of Human Infection With HPAI H5N6 — Sichuan Province
Four months ago the CDC Added A New H5N6 Avian Flu Virus To Their IRAT List of zoonotic influenza viruses with pandemic potential. While this particularly HPAI H5 virus has only been reported in China, and parts of Southeast Asia, the concern is that it could eventually expand its geographic horizons the way that H5N1 and H5N8 have previously.
All of which leads into a new letter, published this week in the EID Journal, that describes recent evolutionary changes in the H5N6 virus, and its likely impact on the effectiveness of China RE-11 poultry vaccine.
Emerging Novel Reassortant Influenza A(H5N6) Viruses in Poultry and Humans, China, 2021
Abstract
A novel highly pathogenic avian influenza A(H5N6) clade 2.3.4.4b virus was isolated from a poultry market in China that a person with a confirmed case had visited. Most genes of the avian and human H5N6 isolates were closely related. The virus also exhibited distinct antigenicity to the Re-11 vaccine strain.
Highly pathogenic avian influenza A(H5N1) virus emerged in China in 1996. H5 viruses have spread to Eurasia since 2003, Africa since 2005, and North America since 2014–2015. These viruses cause huge economic losses to the poultry industry and pose substantial threats to human health. By March 2022, a total of 75 confirmed cases of human infection with influenza A(H5N6) virus had been reported, including 48 cases in China since 2021 (https://www.who.int/teams/global-influenza-programme/avian-influenza/monthly-risk-assessment-summary).
On July 9, 2021, a human case of H5N6 infection was reported in Chongqing, China. One day later, we conducted an epidemiologic survey in the poultry market the patient had visited and collected swab samples from poultry. We identified the samples as H5N6 subtype by using H5- and N6-specific primers and probes. We propagated the virus in 10-day-old specific pathogen–free chicken embryos and designated the isolate as A/chicken/Chonqqing/H1/2021(H5N6) (CK/CQ/H1). We sequenced the viral genome by using the Sanger method and deposited the sequences in GISAID (https://www.gisaid.org; accession nos. EPI1937512–9).
Phylogenetic analysis of the hemagglutinin (HA) genes showed that CK/CQ/H1 and A/Chongqing/02/2021 were closely related genetically and belonged to subclade 2.3.4.4b, along with H5N6 human isolates from Sichuan (2021) and Hunan (2021) Provinces, indicating that their HA genes likely derived from wild bird strains that arrived in China in 2020 (Figure). Phylogenetic analysis of the neuraminidase (NA) genes showed that the isolate were most closely related to H5N6 isolates (subclade 2.3.4.4h) from China (Figure). The H5N8 viruses that arrived in China in late 2020 appear to have reassorted with clade 2.3.4.4h H5N6 viruses already circulating.
(SNIP)
We also evaluated the protective efficiency of Re-11 vaccine against the isolate. We vaccinated 3-week-old specific pathogen–free chickens with the Re-11 vaccine. At 21 days after vaccination, the vaccine induced very high levels of antibody against the vaccine antigen. Then, the birds were intranasally challenged with 106 50% egg infectious dose of CK/CQ/H1. All vaccinated birds displayed no clinical signs and survived, but 2 of them shed virus (Appendix Table 3). The results were inconsistent with those of Cui et al. (8), which may be related to bird species and immune background.
Novel H5N8 viruses of clade 2.3.4.4b virus have spread to China through migratory birds in late 2020 (9,10). These viruses are similar to those that were dominant in Europe from the autumn of 2020 through 2021 but have undergone reassortment since arriving in China, producing novel viruses like CK/CQ/H1. The novel virus we identified is highly pathogenic to both chickens and mice and exhibited distinct antigenicity to the Re-11 vaccine strain, which could not provide complete protection. Under field conditions, birds are unlikely to get sustained high levels of antibody and would more likely be susceptible to infection and virus shedding. New antigen-matched vaccines and more productive measures are needed to prevent and control novel H5N6 infection in poultry and humans.
Dr. Jiang is a veterinary researcher at the China Animal Health and Epidemiology Center. His research interests are the epidemiology and control of avian influenza virus.
As we've discussed previously, poultry vaccines can have a beneficial impact in the control of avian flu, but they must be scrupulously applied, and frequently updated to match circulating strains, else they risk making matters worse.
A few of those past blogs include:
J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China
