After the news of the death of a child from avian influenza A (H5N1) in Cambodia in February 2023, the WHO has published an update on the situation with recommendations and risk assessments. This statement also confirmed that a second case, a family contact of the first, has been reported. Investigations are underway to determine the exposure of the cases to the virus.
What does WHO know?
WHO reports that the first case was reported on 23rd February 2023 by the Cambodia International Health Regulations (IHR) National Focal Point (NFP), with a second case reported on 24th February 2023. These cases are the first to be reported from Cambodia since 2014.
The first case was an 11-year-old girl from Prey Veng province, who was receiving treatment for symptoms at a local hospital from 16th February. She was then admitted to the National Paediatric Hospital on 21st February with severe pneumonia. A sample collected that day tested positive for H5N1 at the National Institute of Public Health and confirmed positive by Institute Pasteur Cambodia, the National Influenza Centre. The child died on 22nd February 2023.
From this index case, 12 close contacts were identified, and samples collected and tested. Investigations confirmed the second case on 23rd February as the father of the child. He is asymptomatic and in isolation at the referral hospital. The other samples were negative.
Cambodia’s public health response
WHO states that a “joint animal-human health investigation” is underway in the province, with the intention of identifying the source and means of transmission. Furthermore, a “high-level government response” is being implemented to limit further spread.
WHO assesses the risk
WHO considers that, as the virus “continues to be detected in poultry populations”, additional human cases “can be expected”. Although the virus “does not infect humans easily” and human-to-human transmission “appears to be unusual”, there is a risk due to exposure to infected poultry or contaminated environments.
Public health measures at human and animal level have been implemented, and further “characterisation” of the virus is expected. However, “available epidemiological and virological evidence suggest that current A(H5) viruses” do not have the “ability of sustained transmission among humans”. Thus, the “likelihood of sustained human-to-human spread is low”.
“Based on available information so far, WHO assesses the risk to the general population posed by this virus to be low.”
Vaccines
Although vaccines against H5N1 have been developed for human use, they are “note widely available”. WHO, through the Global Influenza Surveillance and Response System (GISRS), will continue to monitor the virus’ evolution and recommends continued vaccine development for “pandemic preparedness purposes”.
Further advice
Acknowledging the widespread reports of circulation in birds, “sporadic” cases in humans, and the “constantly evolving nature” of this virus, WHO emphasises the importance of global surveillance. When avian influenza viruses are detected in a specific location, people who are engaged in “high-risk tasks”, such as those that involve interaction with sick or dead birds, should be “provided with and trained in the proper use of appropriate personal protective equipment”.
When a case is suspected or confirmed in humans, a history of exposure to animals and travel should be conducted alongside contact tracing. Although there is no widely available vaccine to protect humans against avian influenza, WHO recommends that all people who interact with birds should have a seasonal influenza vaccination to “reduce the potential risk of reassortment”.
Travellers to locations with known outbreaks of animal influenza should avoid areas such as live animal markets, places where animals are slaughtered, or farms. The usual sensible precautions are encouraged, including regular hand washing and good safety and hygiene practices. However, WHO is not advising the application of travel or trade restrictions at the moment.
For more on avian influenza vaccines and the challenges they present, join us at the World Vaccine Congress in Washington this April.
