Influenza (avian and other zoonotic influenza)

Data and numbers

• Bird flu, swine flu, and other types of influenza viruses can infect humans.
• Direct contact (through handling, slaughtering, slaughtering or processing) or indirect contact (in an environment contaminated with body fluids of infected animals) with infected animals represents a risk for human infection.
• Exposure to animal influenza viruses can cause infection and illness in humans (ranging from mild flu-like symptoms or eye inflammation to severe acute respiratory illness and/or death). The severity of the disease depends on the virus causing the infection and the characteristics of the infected person.
• Currently circulating zoonotic influenza viruses have not shown sustained human-to-human transmission.
• Because influenza viruses have natural hosts in waterfowl, their eradication is impossible. Zoonotic influenza infections will continue to occur. To minimize public health risks, quality surveillance of animals and humans, thorough investigation of every human infection, and risk-based pandemic planning are essential.

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common opinion

There are four types of influenza viruses: A, B, C and D. According to current information, influenza A and B viruses circulate in humans and cause seasonal epidemics of the disease in humans, but only influenza A viruses can cause pandemics. Influenza A viruses are found in many animal species. The emergence of influenza A viruses capable of infecting humans and sustaining human-to-human transmission could lead to an influenza pandemic.

Influenza A viruses are divided into subtypes based on the combination of proteins on the surface of the virus. When animal influenza viruses infect their host species, they are named: avian influenza viruses, swine influenza viruses, equine influenza viruses, canine influenza viruses, etc. These animal influenza viruses, unlike human influenza viruses, do not spread easily between humans or from person to person.

Wild waterfowl are the primary natural hosts for most influenza A virus subtypes. Outbreaks of avian influenza in poultry can have direct and serious consequences for the agricultural sector.

pandemic potential

There will be epidemics in the future, but it is difficult to predict when, where and how they will spread. They can have important health, economic and social impacts. An influenza pandemic occurs when an influenza virus emerges with the ability to cause sustained human-to-human transmission and the population has little or no immunity to the virus. As travel increases around the world, epidemics can spread quickly.

It is unclear whether currently circulating avian, swine, and other influenza viruses will cause future pandemics. However, the wide variety of zoonotic influenza viruses that cause human infection requires enhanced surveillance of animal and human populations, thorough investigation of each zoonotic infection, and planning for pandemic preparedness.

Human signs and symptoms

Exposure to avian influenza viruses can cause infection and illness in humans, ranging from mild flu-like symptoms or eye inflammation to severe acute respiratory illness and/or death. The severity of the disease depends on the virus causing the infection and the characteristics of the infected person. Gastrointestinal and neurological symptoms have been rarely reported. Human infections with subtypes A(H5) and A(H7N9) are associated with higher mortality than seasonal influenza infections.

Epidemiology of human infections

Although rare, human infection with avian and other zoonotic influenza viruses has been reported sporadically. There is a risk of infection in humans through direct or indirect contact with infected animals. Currently circulating zoonotic influenza viruses have not shown sustained human-to-human transmission.

In terms of avian influenza virus, the main risk factor for human infection appears to be contact with infected poultry, either live or dead, or contaminated environments, such as live poultry markets. Other risk factors include slaughtering, plucking and handling the carcasses of infected poultry, and preparing poultry for consumption, especially in households. There is no evidence that A(H5), A(H7N9), or other avian influenza viruses can be transmitted to humans through properly prepared and cooked poultry or eggs. Some human cases of influenza A (H5N1) have been linked to the consumption of dishes made with the raw blood of contaminated birds.

In 1997, human infection with the A(H5N1) virus was reported during a poultry outbreak in the Hong Kong Special Administrative Region of China. Since 2003, this virus has spread in bird populations from Asia to Europe and Africa, and to the Americas in 2021, and has become an epidemic in poultry populations in many countries. The outbreak has resulted in millions of poultry infections, hundreds of human cases, and many deaths. Human cases have been reported mainly in Asian countries, but there have also been reports in Africa, the Americas, and Europe.

In 2013, China reported the first human infection with the H7N9 avian influenza virus. The virus spread among poultry across the country, causing more than 1,500 human cases and many deaths between 2013 and 2019. Since 2019, no further human cases have been reported to WHO. Since 2014, sporadic cases of human infection with avian influenza A (H5N6) have almost exclusively occurred in China. Other avian influenza viruses have also caused sporadic infections in humans.

In terms of swine influenza virus, risk factors include being close to infected pigs or visiting venues where these animals are shown. Sporadic human infection with swine influenza viruses of subtypes A(H1) and A(H3) has also been detected.

diagnosis

Diagnosis of human infections requires laboratory testing, which must be performed in laboratories capable of safely handling and confirming zoonotic infections.

Collect appropriate samples from suspected human cases in dedicated reference laboratories to rapidly and accurately identify and characterize the virus and/or its isolates. This is critical for appropriate response measures.

treat

If a person is suspected of being infected with zoonotic influenza, health authorities should be notified and the case provided with appropriate clinical management, including testing, triage, clinical assessment to classify disease severity, assessment of risk factors for severe disease, and Isolation and treatment (e.g., antiviral medications and supportive care). People with the flu must receive appropriate treatment to prevent severe illness and death.

prevention

Influenza viruses cannot be eradicated and zoonotic infections will continue to occur. To minimize public health risks, quality surveillance of animal and human populations, thorough investigation of every human infection, and risk-based pandemic planning are essential. Public health and animal health authorities should cooperate and share information when investigating human zoonotic influenza cases.

The public should limit contact with animals as much as possible in areas known to be affected by animal influenza viruses, such as farms and establishments where live animals may be sold or slaughtered, and avoid contact with any surfaces that may be contaminated with animal feces. Children, the elderly, pregnant and postpartum women (under 6 weeks old), or those who are immunocompromised should not collect eggs or assist in the slaughter of animals or food preparation.

The public should strictly avoid contact with sick or dead animals, including wild birds, and report dead animals or contact local veterinarians or wildlife authorities to request their removal.

Everyone should practice hand hygiene, preferably with soap and running water (especially if the hands are soiled) or with a hydroalcoholic gel, and in all cases wash as frequently and thoroughly as possible. Especially before and after contact with the animal and its environment.

Everyone should practice good food safety habits: separate raw meat from cooked or ready-to-eat foods, avoid soiling and washing hands, cook food thoroughly, and handle and store meat correctly.

People traveling to or living in countries with known outbreaks of avian influenza should avoid poultry farms, live poultry markets, and areas where animals may be slaughtered if possible. Poultry and contact with any surface contaminated by birds or other animals. Travelers returning from affected areas should notify local health services if they develop respiratory symptoms suspected of being infected with a zoonotic influenza virus.

WHO’s response

WHO continues to monitor avian and other zoonotic influenza viruses through its Global Influenza Surveillance and Response System (GISRS). WHO collaborates with the World Organization for Animal Health (WHOA) and the Food and Agriculture Organization of the United Nations (FAO) to monitor human-animal interfaces, assess associated risks and coordinate responses to zoonotic influenza outbreaks and other public health threats .

Twice a year, WHO consults with experts from WHO collaborating centres, key regulatory laboratories and other partners to review data generated by the Global Influenza Surveillance and Response System and animal health partners on influenza viruses with pandemic potential , and consider whether new vaccine virus candidates are needed to protect against pandemics.

WHO provides guidance based on risk assessments to develop and adapt surveillance, preparedness and response strategies for seasonal, zoonotic and pandemic influenza, and communicates risk assessment results and recommendations to Member States in a timely manner to improve preparedness. and responses at national and global levels. The WHO Pandemic Influenza Preparedness Framework takes a global approach to responding to the next influenza pandemic.