CHP investigate case of Influenza A (H9) infection in 22-month-old girl

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21st February 2024 – (Hong Kong) The Centre for Health Protection (CHP) of the Department of Health (DH) has launched an investigation into a case of influenza A (H9) infection involving a 22-month-old girl. The patient exhibited symptoms of fever and cough with sputum since 15th February and sought medical advice at Union Hospital on 16th February. Hospitalisation was not required at that time. However, today, the Public Health Laboratory Services Branch of the CHP confirmed a positive test result for the influenza A (H9) virus in the patient’s clinical specimen. Further subtyping is still pending. The clinical diagnosis for the patient is avian influenza, and she is currently in stable condition. Arrangements have been made for her to receive further treatment in the isolation ward of Princess Margaret Hospital.

Preliminary investigations conducted by the CHP revealed that the patient had visited Zhongshan during the incubation period. However, she had no recent direct contact with poultry, consumed undercooked poultry, or had contact with other patients. One of her household contacts experienced a sore throat on 17th February but had taken medication, resulting in symptom relief. Other household contacts remain asymptomatic at present. Ongoing investigations are being conducted to gather more information.

The CHP will notify the health authority in Guangdong and the World Health Organisation about this case.

In Hong Kong, novel influenza A infections, including influenza A (H9), are classified as notifiable infectious diseases. Influenza A (H9N2) infection is a mild form of avian influenza. Since 1999, nine cases of influenza A (H9N2) have been reported, with the most recent case being an imported case in 2020. No deaths have been recorded thus far.

A spokesperson for the CHP emphasized the existence of a robust surveillance system in collaboration with public and private hospitals, practising doctors, and at boundary control points. Suspected cases are promptly referred to public hospitals for further investigation.