Avian Flu Diary: Cambodia Reports 7th H5N1 Case of 2024

#18,171

Cambodia's MOH reports their 7th human H5N1 infection for 2024 - and the 2nd one in past two days - with the discovery that a 5 y.o. girl living in the same household as Saturday's case (who is reportedly mildly symptomatic) has tested positive for the virus.

While we don't have word on the exact clade of these two most recent H5N1 cases, they are very likely the older 2.3.2.1c clade of H5N1, which predates the emergence of clade 2.3.4.4b and has been identified in 10 of the last 11 cases in Cambodia.

The (translated) statement from the MOH follows, after which I'll have a bit more.

(translation)

Kingdom of Cambodia
Nation Religion King
That way
Ministry of Health
Press Release

Cases of bird flu in 5-year-old girls

The Ministry of Health would like to inform the public that there is another case of bird flu in 5-year-old girls and was confirmed positive for H5N1 bird flu virus (H5N1) from the National Institute of Public Health on July 7, 2024, living in Po village, Preah Bat Choan Chum commune, Kirivong district, Takeo province. The girl had a fever and was the cousin of a positive 3-year-old boy on July 5, 2024 and lived in the same house. At present, the patient's condition is mild and he is receiving intensive care by doctors. According to the interrogation, about 10 days ago, there was a dead chicken in the village and at home, the patient brought food to eat, the girl touched the dead chicken.

The National and Sub-National Emergency Response Team of the Ministry of Health has been cooperating with the working groups of the Ministry of Agriculture, Forestry and Fisheries and the Ministry of Environment, local authorities at all levels to actively investigate the outbreak of bird flu and respond. According to technical methods and protocols, continue to search for sources of transmission in both animals and humans, and continue to search for suspected cases and exposure to prevent transmission to others in the community, and distribute Tamu to close contacts. And conduct health education campaigns for the people in the above-mentioned villages.

The Ministry of Health would like to remind all people to always pay attention to bird flu because H5N1 bird flu continues to threaten the health of our people and also would like to inform you if you have a fever, cough. Sneezing or shortness of breath and a history of contact with sick or dead chickens during the 14 days before the onset of symptoms, do not go to crowded places or towns and seek consultation and advice.

Get medical check-ups at your nearest health facility on time.

Transmission: H5N1 bird flu is a flu virus that is usually transmitted from sick birds to other birds, but can sometimes be transmitted from birds to humans through close contact with sick or dead birds. Avian influenza in humans is a serious disease that requires timely hospitalization. Although it is not easily transmitted from person to person, if it can metabolize it can be as contagious as the seasonal flu.

Preventive measures: Wash your hands often with soap and water before eating and after contact with birds. Keep children away from birds and birds away from home. Do not eat sick or dead birds and all birds. Made for eating, must be cooked well.

The Ministry of Health will continue to inform the public about information related to public health issues through the Telegram Channel and the official Facebook page of the Ministry of Health, as well as the official Facebook page of the Department of Infectious Diseases and the website www.cdcmoh.gov.kh.

For more information, please contact the Ministry of Health Hotline 115 for free.

While Cambodia has an excellent reputation for reporting and investigating cases or clusters, it takes a bit of luck for these cases to be detected. Mild or moderate cases are more likely to go unrecognized, since the best chance for detection comes when a patient is hospitalized.

Of the 13 H5N1 cases reported by Cambodia over the past 18 months, only 3 have been in adults and all of them survived. Among the 10 children infected - while several had mild symptoms -half (n=5) died.

Younger people (< 40) seem to be more susceptible to H5 infections while the opposite appears true for H7N9 (see H7N9: The Riddle Of The Ages). This affinity for the H5N1 virus to infect younger patients has evoked a number of theories, but has never been adequately explained.

One possibility we've explored, however, is that your first flu exposure may affect your future response to novel flu viruses (see Science: Protection Against Novel Flu Subtypes Via Childhood HA Imprinting).

Up until relatively recently, we thought of influenza viruses as being grouped primarily by HA subtype; H1, H3, H5, H7, etc.

But, as the chart below illustrates, the 18 known subtypes are divided into two basic groups; Group 1 and Group 2.

Some studies suggest that the first HA group you are exposed to may affect your ability to fight infection by viruses from the other group. A few past blogs include:

Science: Protection Against Novel Flu Subtypes Via Childhood HA Imprinting

PLoS Path.: Childhood Immune Imprinting to Influenza A
Nature Comms: Middle-Aged Individuals May Be in a Perpetual State of H3N2 Flu Virus Susceptibility

This childhood imprinting may help to explain why (HA Group 2) H7N9 cases in China skewed heavily to those > 50, while (HA Group 1) H5N1 cases generally affected those under the age of 40 (see chart below).

Regardless of the actual reasons behind it, this track record of H5N1 hitting children particularly hard has long been a concern. Past performance may not predict future results, of course, since different clades or genotypes of H5Nx might produce vastly different results.