Global Summary of Human Cases of H5N1 Bird Flu from August 2025 to June 2026

Overview

There are many different subtypes of avian influenza (bird flu) viruses; A(H5N1) viruses have accounted for most human cases reported globally since 1997. This report focuses on human cases of H5N1 bird flu reported internationally since August 4, 2025, when CDC last published a summary of human infections with avian influenza A(H5N1) viruses (H5N1 bird flu) reported internationally.

Since August 2025, there have been an additional 12 cases of H5N1 bird flu reported internationally. These A(H5N1) virus infections occurred in three countries: Bangladesh, Cambodia, and India. As of June 10, 2026, 1,022 cases have now been reported worldwide since 1997. Most A(H5N1) virus infections in other countries have been associated with a different clade (i.e., genetic grouping) of A(H5N1) viruses than cases reported in the United States, and generally have a high mortality rate. International cases have mostly occurred after direct or close exposure to infected sick or dead poultry.

Five subtypes of bird flu viruses are known to have infected people. These are called A(H5), A(H6), A(H7), A(H9), and A(H10) viruses. Among these, A(H5), A(H7) and A(H9) viruses have caused the most human infections.

Summary of H5N1 bird flu human cases

Bangladesh

Three human bird flu cases with A(H5N1) virus infection (clade 2.3.2.1a) were reported to have occurred in Bangladesh since August 2025. The first infection was reported in mid-August 2025, in a child whose family purchased chickens from a local market before the child got sick. The second case, reported in February of 2026, was fatal. This case was in a child who had been exposed to sick poultry. Bangladesh reported a third H5N1 bird flu case in a child in April 2026. Investigations found the child had been exposed to household poultry.

Cambodia

Cambodia has reported eight human infections with A(H5N1) viruses since CDC's August 2025 summary. Four of these cases occurred in 2025, and four in 2026. All the infections happened after exposure to sick or dead domestic birds directly, or to their environments. Among the viruses for which that information is available, the cases were associated with clade 2.3.2.1e viruses. This clade is similar to viruses that have circulated in Cambodia since 2023.

2025 human H5N1 bird flu cases

• Child - Symptom onset: July
• Child - Symptom onset: September
• Child - Symptom onset: October
• Adult - Symptom onset and death: November

2026 human H5N1 bird flu cases

• Adult - Symptom onset: February
• Adult - Symptom onset: March
• Child - Symptom onset: March
• Adult - Symptom onset and death: April

India

India has reported one human case of H5N1 bird flu since CDC's August 2025 summary. This infection occurred in a child in March. Genetic sequencing indicated that the virus associated with this infection was clade 2.3.2.1a. This is closely related to viruses previously reported by India and Bangladesh in 2025. Backyard poultry in the village with two isolated poultry deaths suggests a possible environmental exposure.

Conclusion

While rare, these H5N1 bird flu cases in humans underscore the need for strong systems to monitor and prepare for influenza, including robust surveillance and testing, to understand which influenza viruses are circulating and their effect on human health. This is critical for pandemic preparedness and for protecting Americans at home and abroad.