#18,794
Overnight the WHO published their June 2025 update on novel influenza (covers May 28th-July 1st), which adds 10 human H5N1 cases, 3 human H9N2 infections, and a 6th H10N3 case in China.
Although the H9 and H10 cases were previously reported (see WHO WPRO Reports 6th H10N3 Case & 3 Additional H9N2 Cases In China), as were 8 H5N1 cases from Cambodia last month, there are 2 previously unannounced H5N1 cases in today's report (Bangladesh & India).
Given the cutoff date of July 1st, Cambodia's latest case was not included. First, the summary, then we'll dig into some specifics on last month's cases.
Influenza at the human-animal interface
Summary and risk assessment, from 28 May to 1 July 20251
• New human cases : From 28 May to 1 July 2025, based on reporting date, the detection of influenza A(H5N1) in nine humans, influenza A(H9N2) in three humans and influenza A(H10N3) in one human were reported officially. Additionally, one human case of infection with an influenza A(H5N1) virus was detected.
• Circulation of influenza viruses with zoonotic potential in animals: High pathogenicity avian influenza (HPAI) events in poultry and non-poultry continue to be reported to the World Organisation for Animal Health (WOAH).3 The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemic potential.4
• Risk assessment: Sustained human to human transmission has not been reported from these events. Based on information available at the time of the risk assessment, the overall public health risk from currently known influenza viruses circulating at the human-animal interface has not changed remains low. The occurrence of sustained human-to-human transmission of these viruses is currently considered unlikely. Although human infections with viruses of animal origin are infrequent, they are not unexpected at the human-animal interface.
• IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005).6 This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin (HA) gene (or protein) is not a mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human population. Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.
A little over 5 weeks ago, in the May 2025 WHO Summary, we learned of 2 previously undisclosed H5 cases (clade 2.3.2.1a ) from Bangladesh; both collected from young children in Khulna Division last spring.
Today's update provides a third case, this time from Chittagong division (> 250 Km to the east).
On 31 May 2025, Bangladesh notified WHO of one confirmed human case of avian influenza A(H5) in a child in Chittagong division detected through hospital-based surveillance. The patient was admitted to hospital on 21 May with diarrhea, fever and mild respiratory symptoms and a respiratory sample was collected on admission.
On 28 May, the IEDCR confirmed infection with avian influenza A(H5) through RT-PCR. The N-type was later confirmed as N1. The patient has recovered, and exposure to backyard poultry was reported prior to symptom onset. No further cases were detected among the contacts of the case.
This is the 11th human infection with influenza A(H5N1) notified to WHO from Bangladesh since the first case was reported in the Dhaka division in 2008 and the third confirmed case in 2025.
The second new case (from India) remains somewhat of a mystery. Not only is the report quite brief, the location provided (Khulna State) is a bit confusing, as Khulna is located in Bangladesh, not India.
A(H5N1), India
A human infection with an H5 clade 2.3.2.1a A(H5N1) virus was detected in a sample collected from a man in Khulna state in May 2025, who subsequently died. Genetic sequence data are available in GISAID (EPI_ISL_19893416; submission date 4 June 2025; ICMR-National Institute of Virology; Influenza).
Today's report provides a more extensive review of the 8 cases reported by Cambodia last month:
Brief updates on the H9 and H10 cases are also included:
Since the last risk assessment of 27 May 2025, three human cases of infection with A(H9N2) influenza viruses were notified to WHO from China on 9 June 2025. The cases were detected in Henan, Hunan and Sichuan provinces. Two infections were detected in adults who were also hospitalized. The cases had symptom onset in May 2025 and have recovered. All cases had a known history of exposure to poultry prior to the onset of symptoms. No further cases were detected among contacts of these cases and there was no epidemiological link between the cases.
On 9 June 2025, China notified the WHO of one confirmed case of human infection with avian influenza A(H10N3) virus in an adult from Shaanxi Province, with a history of asthma. Symptom onset occurred on 21 April, and the patient was admitted to hospital with pneumonia on 25 April. At the time of reporting, that patient was under treatment and improving.
According to the epidemiological investigation, a history of exposure to backyard poultry in Inner Mongolia was reported. The patient is a farmer and raises chickens and sheep. Environmental samples did not test positive for influenza A(H10) viruses. All close contacts tested negative for influenza A and remained asymptomatic during the monitoring period.
Since 2021, China has notified WHO of a total of six confirmed human cases of avian influenza A(H10N3) virus infection.
In addition to these case updates, the WHO once again implores member nations to abide by the 2005 IHR regulations which require prompt notification of the WHO of all human infections caused by novel flu subtypes.
According to a report 2 years ago (see Lancet Preprint: National Surveillance for Novel Diseases - A Systematic Analysis of 195 Countries) many member nations still lack the capability to fully investigate cases, while others simply choose not to for economic, societal, or political reasons.
For a multitude of reasons, the cases that do get reported are almost certainly just the tip of a much larger iceberg. And as this report illustrates, there is more than just H5N1 percolating in the wild.
