Objective To analyze the clinical manifestations of a severe child case of H9N2 Avian influenza virus infection in Nanning and epidemiological features of disease, to explore its possible source of infection, transmission route and risk factor and to provide a scientific basis for early identification, clinical treatment and formulation of prevention and control strategies for H9N2 avian influenza in the future.
Methods A retrospective analysis was conducted on the clinical data of a severe child case of H9N2 Avian influenza virus infection admitted to a hospital in Guangxi Zhuang Autonomous Region on February 4, 2024. An epidemiological investigation was conducted, bronchoalveolar lavage fluid from the child and throat swabs from close contacts were collected for genetic sequence analysis. The throat swabs from personnel in the live poultry market and external environment samples were collected for testing.
Results The pediatric patient had a history of contact with live poultry three days ago prior to onset, with an acute onset on February 1. The patient initially presented with a cough and fever. It progressed to severe pneumonia on February 4, with chest imaging showing partial pulmonary consolidation, atelectasis and pleural effusion. The case tested positive for Mycoplasma pneumoniae immunoglobulin M on February 6. The H9N2 Influenza A virus was tested in the bronchoalveolar lavage fluid sample on February 6 and the patient was isolated and treated. The case tested positive for the Influenza B virus on February 13. The case was discharged on February 20. No other contacts were found to be infected with H9N2 Avian influenza virus after the onset of the case. The samples collected from the pediatric patient´s home external environment tested negative of H9N2 Influenza A virus, while the mixed samples collected from chickens and live poultry stores both tested positive of H9N2 Influenza A virus. It was deficient in serological data on the H9N2 Influenza A virus among the population in live poultry markets.
Conclusion Children under 5 years old with mixed infection of Mycoplasma pneumoniae who are infected with H9N2 Avian influenza virus have a high risk of developing severe symptoms. Clinical doctors should be alert to the possibility of avian influenza when receiving patients with a history of contact with live poultry, timely targeted symptomatic supportive treatment is crucial and relevant departments need to strengthen the monitoring of Avian influenza virus in the poultry market environment.


(date of manuscript submission 2025-01-24)