Mexico’s September human bird flu case confirmed as H5N2

A human avian influenza case reported in Mexico in late September has been confirmed as H5N2, making it the country’s second known human infection with this subtype and the second reported worldwide, according to health officials.

The case was initially classified only as avian influenza A(H5) when it was announced on September 30. The Pan American Health Organization (PAHO) said further laboratory analysis has now confirmed the virus as H5N2.

Mexican health officials reported that the patient was a 23-year-old woman from Mexico City who had no recent travel history. PAHO said she began experiencing respiratory symptoms on September 14, including cough and runny nose, which progressed to fever, painful swallowing, chest pain, and hemoptysis, or coughing up blood.

A sample collected on September 29 tested positive for unsubtypeable influenza A, and influenza A(H5) was confirmed by RT-PCR the following day. She was treated with oseltamivir and discharged from the hospital on October 11.

Health authorities noted the presence of several birds in the courtyard of the patient’s building, including a poultry bird and pigeons, along with bird droppings found in multiple areas, such as a poorly sealed cistern supplying water to the apartments. A dog also lived in the home. Samples taken from the animals tested positive for influenza A(H5).

Mexico has reported two previous human avian influenza infections. The country’s first occurred in 2024 and involved H5N2, which was also the world’s first reported human case of this subtype and resulted in the death of a 59-year-old man in the neighboring State of Mexico.

A second case was reported in April 2025, when a 3-year-old girl from a rural community in northern Mexico died after developing severe complications linked to H5N1 avian influenza, the country’s first reported human infection with that subtype.

The confirmation of Mexico’s latest H5N2 case follows the first reported human infection with H5N5 worldwide, identified in the United States. The Washington State Department of Health said an older adult with underlying health conditions died after being hospitalized since early November.