Infection of humans with bird flu A (H5N8) – Russian Federation

On February 18, 2021, the National IHR Contact Person for the Russian Federation notified the WHO of the detection of avian influenza A (H5N8) in seven human clinical samples. These are the first recorded discoveries of bird flu A (H5N8) in humans. Positive clinical samples were collected from poultry farm workers who participated in an operation to respond to the outbreak of bird flu A (H5N8) detected on a poultry farm in the Astrakhan region of the Russian Federation. Laboratory confirmation of seven samples was performed by the State Research Center for Virology and Biotechnology VECTOR (Reference Laboratory WHO H5). The age of seven positive cases ranged between 29 and 60 years, and five were female.

Between December 3 and 11, a total of 101,000 of the 900,000 laying hens died on the farm. This high mortality rate has prompted an investigation. Samples were collected from these birds, and the Russian Regional Veterinary Laboratory performed the initial detection of bird flu A (H5N8). On December 11, the outbreak was confirmed by the World Animal Health Reference Laboratory (OIE) and the Federal Center for Animal Health (FGBI-ARRIAH) in Vladimir, Russian Federation. Operations to combat the outbreak of the epidemic began immediately and continued for several days due to the large size of the poultry farm.

Cases remained asymptomatic throughout the follow-up period (several weeks). Control nasopharyngeal swabs were collected during the medical observation period and tested negative for avian influenza A (H5N8). No obvious clinical manifestations were reported from any medically supervised farm worker, family members, or other close contacts in seven cases. In addition, acute and convalescent sera were collected from seven positive human cases for serological testing. The results indicated a recent infection.

Influenza A (H5N8) viruses isolated from this poultry outbreak in Astrakhan belonged to avian influenza A (H5Nx) virus cluster 2.3.4.4b. In 2020, avian influenza A (H5N8) viruses were also detected in poultry or wild birds in Bulgaria, the Czech Republic, Egypt, Germany, Hungary, Iraq, Japan, Kazakhstan, the Netherlands, Poland, Romania, the United Kingdom and the United Kingdom. Russian Federation.

Public health response

Upon receiving the initial signal of a probable outbreak of highly pathogenic avian influenza (HPAI) on a poultry farm on 3 December 2020, national authorities took immediate measures, including the cessation of the poultry production cycle and the transport of products from the affected farm.

Between 11 and 18 December, several measures were taken, including the shooting and disposal of poultry, eggs, litter and the disinfection of contaminated premises as part of the epidemic response activities.

During and after removal of all poultry, nasopharyngeal samples and serum samples were collected from poultry farm workers and staff involved in the poultry outbreak response on the farm. Surveillance activities have been intensified, both inside and outside the prison area. A total of 24 close contacts of confirmed cases were identified and found. A total of 150 individuals were monitored for clinical indications of respiratory disease and received antiviral prophylaxis. No symptoms were reported among these individuals.

Complete sequencing of the avian influenza A (H5N8) virus genome isolated from poultry and from one of seven human cases transferred to the Global Influenza Sharing Initiative (GISAID) database on February 20, 2021. Genetic and phenotypic characterization of the virus is in process.

The WHO follows with public health authorities in the Russian Federation, including the implementation of public health measures guaranteed by such events, and with the WHO Global Influenza Surveillance and Response System (GISRS) on further analysis and evaluation of virus and serum samples. On February 20, a special briefing was organized by the head of the Federal Service for Supervision of Consumer Protection and Human Welfare to inform the Russian state media about these cases and implications.

WHO risk assessment

Since 2004, avian influenza A (H5) viruses have spread from Asia to Europe via wild birds. Genetic log 2.3.4.4 H5 viruses were often reclassified as other avian influenza viruses, resulting in avian influenza A (H5N1), A (H5N2), A (H5N3), A (H5N5), A (H5N6) and A ( H5N8) viruses, some of which have been found in birds in many countries.

In the Russian Federation, bird flu A (H5N8) logs 2.3.4.4 was first isolated in 2014 in a wild bird in the northern part of the Russian Far East.

As mentioned earlier, all seven cases with PCR positive results were clinically asymptomatic. All close contacts of these cases were clinically monitored and no one showed signs of clinical disease. Infections with bird flu viruses of the same log (H5 log 2.3.4.4) have been reported from China since 2014 in humans who have been exposed to infected birds. The likelihood of human influenza A (H5N8) virus infections is considered low.

Further genetic and antigen characterization and information on seroconversion among positive case contacts are needed for a complete risk assessment.

The development of a candidate virus against zoonotic influenza for potential use in human vaccines, coordinated by the WHO, remains an essential component of the overall global strategy for pandemic influenza preparedness.

Based on currently available data, the risk of human-to-human transmission remains low.

WHO advice

These cases do not alter the current WHO recommendations on public health measures and animal and seasonal influenza surveillance, which should continue to be implemented. Respiratory transmission occurs mainly by droplets and is spread by unprotected coughing and sneezing. Airborne transmission of influenza virus can occur over short distances, especially in crowded enclosed spaces. Hand contamination, direct inoculation of viruses, exposure to infected birds or viruses contaminated with materials or the environment are potential sources of infection.

When bird flu viruses circulate in an area, people involved in specific high-risk tasks, such as sampling sick birds, shooting and disposing of infected birds, eggs, garbage and cleaning contaminated areas, should be trained on how to protect themselves and the proper use of personal protective equipment. (PPE). Local health authorities should register the people involved in these tasks and closely monitor them for seven days after the last day of contact with the poultry or their environment.

Due to the constantly evolving nature of influenza viruses, the WHO continues to emphasize the importance of global surveillance to detect virological, epidemiological and clinical changes associated with circulating influenza viruses that may affect human (or animal) health and timely virus sharing for risk assessment.

All potential new influenza virus infections in humans need to be thoroughly investigated. All human infections caused by a new subtype of influenza must be reported under the International Health Regulations (IHR), and IHR States Parties must immediately notify the WHO of any laboratory-confirmed cases of recent human infection caused by a new influenza A subtype with the potential to cause a pandemic (see case definitions for diseases requiring IHR notification ). Evidence of disease is not required.

In the event of confirmed or suspected human infection, a thorough epidemiological investigation of the history of animal exposure, travel, and contact seeking should be conducted, even pending confirmatory laboratory results. Epidemiological research should include the early identification of unusual respiratory events that could signal the transmission of a new virus from person to person. Clinical samples collected from the time and place of the case should be tested and sent to the WHO Collaboration Center for further characterization.

Travelers to countries with known bird flu epidemics should avoid farms, contact with animals in live animal markets, entering areas where animals can be slaughtered, or contact with any areas that appear to be contaminated with animal feces. Passengers should also wash their hands frequently with soap and water. Travelers should follow good food safety and good food hygiene practices.

Based on currently available information, the WHO advises that no special checks be conducted for travelers at points of entry or restrictions on travel and / or trade with the Russian Federation.

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