Overview / History

The influenza A(H3N8) strain does not cause severe disease in birds. It has previously been detected in birds in China, and other strains of A(H3N8) are known to circulate in horses (equine) and dogs (canine). Despite large outbreaks since the 1960s, the equine form is not known to be transmissible to humans.

The first identified human case of influenza A(H3N8) occurred in April 2022 in Henan Province, China. A 4-year-old boy developed fever, cough and shortness of breath. His condition worsened, leading to hospitalisation five days after symptom onset with severe pneumonia and respiratory failure. He was treated with antiviral medication. Since then, at least two other cases have been reported, both in China, with one being fatal. The fatality involved an individual with underlying health conditions who had been exposed to poultry and wild birds before falling ill.

Mode of spread

Animals

Transmission

Humans typically contract avian flu through contact with birds. However, some human infections have occurred without known direct contact with birds.

Symptoms

Similar to other bird flu strains, H3N8 symptoms resemble those of ordinary flu. From the few known cases, symptoms reported have included fever, cough and shortness of breath. The symptoms can progress, leading to severe pneumonia and respiratory failure.

Diagnosis

Highly specialised testing of respiratory samples is required to diagnose H3N8. Clinical signs and history of contact with poultry or travel to an affected area may indicate bird flu infection.

Treatment

It is unclear whether H3N8 can be effectively treated with antiviral medications like Tamiflu and Relenza. One of the cases has documented antiviral therapy during hospitalisation.

Vaccination

There are no vaccines for humans against H3N8. However, equine vaccines are available.

Prevention

To reduce the risk of infection, avoid contact with birds and other animals and their environment:

• Do not go to live animal markets, poultry farms or pig farms.
• Do not handle any birds, even if they appear healthy. Prevent children from doing so.
• Avoid touching any surfaces that may be contaminated by bird droppings. Do not swim in any body of water that is used by birds.

Always maintain high levels of personal hygiene:

• Frequent hand washing is very important, particularly before and after food preparation and before eating.
• Cook all poultry and poultry products thoroughly, including eggs.

Consider getting the influenza vaccine. While it does not protect against bird flu, it reduces the risk of a "co-infection" with human influenza.

Risk to travellers

Travellers who avoid live poultry markets and direct contact with birds are at very low risk.