#19,124
After going a couple of months without any reports, last week Hong Kong's CHP announced 2 new H9N2 cases on the Mainland, and this morning has announced 3 more.
First last weeks announcement:
Followed by today's:
As is typical, we only get the barebones details from the CHP reports. The WHO Western Pacific Regional Office (WPRO) has published slightly more information in their latest 2 weekly reports, but are also somewhat lacking in details.
For the first 2 cases:
Human infection with avian influenza A(H9N2) virus
From 27 March to 9 April 2026, two new cases of human infection with avian influenza A(H9N2) virus were reported to WHO in the Western Pacific Region.
The first case was a male child under five years of age from Guangdong Province, China, who was hospitalized with bronchopneumonia and severe pneumonia and was laboratory-confirmed with influenza A(H9N2) on 4 February 2026.
He had no direct contact with live poultry but may have had indirect exposure through a family member working at a poultry farm. He recovered and was discharged on 12 February.
The second case was a 63-year-old male from Guangxi Province with underlying conditions. Following contact with sick poultry in late January, he developed symptoms on 5 February 2026 and was laboratory-confirmed with influenza A(H9N2) on 11 February. He recovered and was discharged on 17 February.
The three cases reported today were described as:
Human infection with avian influenza A(H9N2) virus
From 10 to 16 April 2026, three new cases of human infection with avian influenza A(H9N2) virus were reported to WHO in the Western Pacific Region. All three cases were children under 10 years of age from China.
The first case is a male with comorbidities from Guangdong Province, with symptom onset on 23 February 2026. He was hospitalised with severe pneumonia on 23 February and was discharged on 25 March.
The second case is a female from Yunnan Province, with symptom onset on 3 March; the third case is a male from Jiangxi Province, with symptom onset on 20 March. Both cases developed mild symptoms only and did not require hospitalisations.
The first and second cases had exposure to poultry, whereas no clear direct poultry exposure was identified for the third case. However, environmental samples from live poultry stalls in the market routinely visited by the family member of the third case tested positive for H9.
No additional cases were reported from close contacts of the cases. Since December 2015, a total of 162 cases of human infection with avian influenza A(H9N2), including two deaths (both with underlying conditions), have been reported to WHO in the Western Pacific Region. Of these, 159 were reported from China, two were from Cambodia, and one was from Viet Nam.
What we can piece together from the combined reports is that:
- 4 of the 5 cases were in young children, while 1 was in a 63 y.o. man.
- 2 were characterized as having `severe' pneumonia, 1 other was hospitalized (M, 63) but no details were offered, while 2 others developed mild symptoms and were not hospitalized
- 3 of the 5 cases reportedly had direct contact with sick poultry, while 2 did not
- Both cases without poultry contact may have had indirect contact via family members who worked with poultry, or visited a LBM (Live Bird Market)
While we've seen cases with no reported direct contact to poultry before, it is a bit unusual to have two cases where `indirect exposure' via a family member is mentioned as a possibility.
H9N2 is typically described as being a mild infection, but here 3 of the 5 were hospitalized, with two cited as having `severe pneumonia'. While there may have been comorbidities that impacted these patients, none were mentioned.
We've seen increasing concerns from Chinese scientists that H9N2 is evolving, and is acquiring mammalian adaptations (see EM&I: Enhanced Replication of a Contemporary Avian Influenza A H9N2 Virus in Human Respiratory Organoids). The authors wrote:
In summary, we demonstrated that a recent H9N2 virus is more adapted to humans, and is able to replicate to high titres in both upper and lower human respiratory tract which may confer higher person-to-person transmissibility and virulence.
Last October, in China CDC Weekly: Epidemiological and Genetic Characterization of Three H9N2 Viruses Causing Human Infections, we looked at a local CDC investigation into 3 pediatric cases which were reported last April from Changsha City, Hunan Province, China.
Their report found a number of indicators of increased mammalian adaptation within the virus, including an enhanced ability to infect upper respiratory (α2,6-sialic acid) tract receptors, and a number of HA protein mutations, including; H191N, A198V, Q226L, and Q234L.
