The Hong Kong Centre for Health Protection (CHP) is investigating a locally acquired case of human infection with influenza A (H9) in a two-year-old boy. The child, a resident of Sha Tin District, remains in stable condition at Princess Margaret Hospital after testing positive for the virus following exposure to a live poultry stall at a local market.
How does influenza A (H9) transmit to humans?
Human infection with influenza A (H9) typically occurs through direct contact with infected poultry or contaminated environments. According to the CHP, the two-year-old patient visited Wo Che Market in early June, where he touched surfaces near a shop selling live chickens. While the child’s household does not keep poultry and he did not consume undercooked meat, the investigation identified the market visit as the primary point of exposure. The Food and Environmental Hygiene Department (FEHD) has since collected environmental samples from the market to assess the viral presence.
The World Health Organization (WHO) has recorded over 160 human cases of influenza A (H9) globally over the last decade. Most cases present with mild respiratory symptoms rather than severe illness.
What is the current risk of human-to-human transmission?
Public health authorities maintain that the risk of sustained human-to-human transmission remains low. The WHO risk assessment indicates that the influenza A (H9) virus has not acquired the necessary biological traits to spread efficiently between people. In this specific case, the patient’s six household contacts remain asymptomatic, and the staff at the poultry shop have also shown no signs of illness, according to the CHP.
Comparing H9 to other avian influenza strains
While H9 infections are generally characterized by mild clinical outcomes, they are monitored closely due to their relationship with other avian viruses. Unlike highly pathogenic strains that often cause severe mortality in both birds and humans, H9 is considered low pathogenic. Health experts monitor these cases to ensure the virus does not undergo reassortment—a process where the virus swaps genetic material with human influenza strains, potentially increasing its pandemic potential.
Avoid direct contact with live poultry or bird droppings when visiting wet markets. Always practice thorough hand hygiene after touching surfaces in areas where live animals are kept.
What steps are health officials taking next?
The CHP is currently conducting whole genome sequencing on the virus sample to track any mutations that might alter its behavior. By comparing the genetic profile of this case with previous reports, researchers aim to determine the exact origin of the strain. The investigation remains ongoing, with officials continuing to monitor the patient’s contacts and the environment at the affected market to prevent further transmission.
Frequently Asked Questions
- Can I catch H9 from eating chicken? No, the virus is not transmitted through the consumption of properly cooked poultry.
- What are the symptoms of H9? Most reported cases present with mild symptoms, such as fever and diarrhea.
- Is there a vaccine for H9? Currently, there is no widely available human vaccine for this specific strain, as public health efforts focus on preventing exposure.
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