WHO warns of risks to humans from ongoing bird flu outbreaks in animals

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WHO warns of risks to humans from ongoing bird flu outbreaks in animals

WHO warns of risks to humans from ongoing bird flu outbreaks in animals.

On June 27, 2023, the National Coordinating Center of the International Health Regulations in Poland notified the World Health Organization of the abnormal death of cats in the country.

As of July 11, a total of 29 positive cases of A(H5N1) avian influenza were found in 47 samples including a captive caracal, accounting for 62% of the total samples.

WHO warns of risks to humans from ongoing bird flu outbreaks in animals

Infected cats exhibited severe symptoms, including respiratory problems, bloody diarrhea, neurologic symptoms, and complications such as pneumonia, leading to rapid disease progression and, in some cases, death.

Fourteen cats were reported to have been euthanized and 11 others died, the most recent on June 30.

Previously, there were reports of sporadic infection of cats with H5N1 avian influenza virus, but this outbreak in Poland is by far the one with the largest number of infected cats in a country and the widest spread.

The source of the virus that the infected cats were exposed to is not yet clear, and the epidemiological investigation is still in progress.

The source of the virus in Poland

Genome analysis of 19 viruses in this outbreak showed that these viruses all belonged to the H5 influenza 2.3.4.4b branch virus and were highly related to each other.

Furthermore, these viruses, which are similar to viruses of the influenza A(H5N1) 2.3.4.4b clade, have been circulating in wild birds and recently caused outbreaks in poultry in Poland.

The exact route by which cats become infected with the virus has yet to be determined and may include direct or indirect contact with infected poultry or its environment, consumption of infected poultry, or ingestion of virus-contaminated food.

Among the 25 cats with available information, 2 were outdoor cats, 18 were indoor cats that could enter the balcony, terrace or backyard, and 5 were indoor cats that could not enter the outdoor environment. Seven cats reportedly had access to wild birds.

Low risk of human infection

According to WHO’s risk assessment, to date, there have been no documented cases of human infection with avian influenza A(H5N1) virus from contact with infected cats.

As of July 12, 70 people who had been in contact with the confirmed cat had completed self-monitoring, and no one had reported symptoms of infection.

Poland has the capacity to detect human infection after contact with infected cats. Therefore, the general population has a low risk of infection from contact with infected cats, and cat owners and veterinarians, who have occupational contact with related animals, have a low to moderate risk of infection without proper protection.

At the regional level, the risk of human infection is low due to the intensification of animal surveillance activities for avian influenza in Europe since September 2022, and no human infections with feline A(H5N1) viruses have been reported so far , although domestic cats have been confirmed to be infected with A(H5N1) virus in Poland. However, risk assessments may change due to uncertainties surrounding the event, including the source of infection.

Epidemiological study of H5N1

Since the end of 2021, an unprecedented number of H5N1 outbreaks in poultry and wild birds have been reported globally. As of June 2023, the H5N1 influenza 2.3.4.4b clade virus has dominated Asia, Europe, the Americas, and Africa.

Infections are also increasing in non-avian species, including terrestrial wild (often scavengers) and marine mammals, and sporadically in farmed or captive mammalian species, possibly due to exposure to infected poultry and contaminated environments.

Since 2020, WHO has received a total of 12 reports of human infection with the A(H5N1) avian influenza 2.3.4.4b lineage virus, of which 4 were severe cases and 8 were mild or asymptomatic cases.

It is unclear whether the virus detected in mild or asymptomatic cases is due to infection or temporary nasal contamination.

Infection with the virus in humans can cause severe disease with a high mortality rate.

Most of the human cases identified to date have been associated with close contact with infected poultry and contaminated environments.

Public health response

Poland has adopted a series of public health response measures to deal with the outbreak, including providing cat owners with health self-assessment questionnaires and requiring them to conduct self-health monitoring, providing regular updates and information sharing, conducting epidemiological investigations to determine the source of the virus, publishing Precautions to protect cat owners and those exposed to suspected infected animals.

WHO is closely monitoring the situation and is working closely with the animal and public health sectors, regional bodies, FAO, OIE and other partner agencies in Poland and globally.

At the same time, the existing influenza A (H5N1) candidate vaccine virus (CVV) is evaluated through the Global Influenza Surveillance and Response System (GISRS) to ensure the development of a vaccine that can effectively prevent the outbreak.

WHO recommendations

Based on the available information on this outbreak, WHO currently does not recommend restricting travel or trade with Poland.

WHO calls on the world to continue to strengthen influenza surveillance and information sharing to detect and assess new influenza viruses that pose a threat to human health and curb their spread.

Patients who have been in contact with infected animals or who have confirmed infection should be registered with the local health department and be closely monitored for early detection of the virus and timely clinical management.

Public health and animal health departments should cooperate closely in information sharing, joint risk assessment and response to zoonotic influenza outbreaks, adhering to the “One Health” approach.

WHO, FAO and OIE issued a joint situation analysis and recommendations to countries on the ongoing avian influenza outbreak in animals and the risks it poses to human health.

At the same time, WHO and relevant agencies will continue to monitor the situation, provide prevention and control recommendations, and promote global cooperation to protect animals, humans, and the economy.