#17,719
On Sunday the Cambodian MOH Reported A Human H5N1 Case - the third to be reported in that country in 2023 (see previous cases) - after a lull in reporting of nearly a decade. This first case (a 50-year old man) was followed a day later by reports on the infection and death of a 2-year-old girl in an adjacent province.
Both cases reported contact with sick or dying chickens, and in one case dead chickens were said to have been distributed to neighbors and friends for consumption.
As we saw in Preprint: A Timely Survey of Knowledge, Attitudes, and Practices Related to Avian Influenza (H5N1) in Rural, Cambodia - despite a long history of H5N1 outbreaks - sick or dead chickens are often consumed by locals.
We learned on Wednesday that these two latest cases stemmed from clade 2.3.2.1c - an older lineage of avian flu which predates our current clade 2.3.4.4b epizootic - but one that has been linked to fatal human infections in the past.
This is the same H5 clade isolated from a Nurse who returned to Alberta, Canada from a trip to China (see Alberta Canada Reports Fatal (Imported) H5N1 Infection) in late 2013, and similar to one that killed a captive tiger in Jiangsu Province - also in 2013 - with both cases exhibiting unusual neurological symptomology.
So far, Cambodia has not reported any additional cases, although media reports indicate that surveillance is ongoing. Late yesterday the U.S. CDC published the following statement.
Cambodia: Two Fatal Human Influenza A/H5N1 (Bird Flu) Virus Infections
October 12, 2023 – Two fatal human infections with highly pathogenic avian influenza (HPAI) A H5N1 (bird flu) virus have been reported by Cambodia. These are the third and fourth human infections with HPAI H5N1 bird flu reported by Cambodia this year. The infected patients lived in two different provinces, and both infections likely resulted from exposure to infected poultry. Recent die-offs in poultry caused by H5N1 bird flu have been reported in parts of Cambodia, so sporadic H5N1 bird flu human infections are not surprising. An investigation to try to confirm the source of the infections and detect any additional cases is ongoing.
These two fatal infections in Cambodia were in a child and an adult, both of whom had exposure to poultry prior to their illness. The infections were identified through influenza surveillance and alert systems. One patient presented with severe symptoms at an influenza sentinel surveillance hospital, and the other patient’s death at a hospital triggered an alert to the local rapid response team. Close contacts of both patients, including potentially exposed health care workers, are being monitored closely. At this time, there is no indication that these two human infections with H5N1 pose a threat to the U.S. public.
Genetic sequencing of patient specimens by the Institut Pasteur du Cambodge (IPC) and the Cambodian National Institute of Public Health (NIPH) has identified these viruses as being H5 clade 2.3.2.1c, which has circulated in Cambodia among birds/poultry for many years. These viruses have resulted in rare sporadic human infections in the past, including two cases in Cambodia in February 2023. This H5 clade 2.3.2.1c virus in Cambodia is different from the H5 virus that has caused wild bird and poultry outbreaks in the United States.
The U.S. CDC is working closely with the Ministry of Health’s Cambodia Communicable Disease Control (C-CDC) Department, the National Institute of Public Health in Cambodia, the Ministry of Agriculture, Forestry and Fisheries, IPC, the World Health Organization, FAO, and the Wildlife Conservation Society of Cambodia to respond to these cases. We will provide updates as new information becomes available.
This resurgence of clade 2.3.2.1c is obviously a concern, but it is too soon to know if this is a temporary blip, or a worrisome trend. Given its presence in local poultry, detection of additional human infections would not be unexpected.
As we've seen the past few years with clade 2.3.4.4b, the `right' reassortment or antigenic changes can breathe new life into an existing lineage.
Whether that has happened with clade 2.3.2.1c remains to be seen. But this is a reminder that while we are watching one threat (H5N1 clade 2.3.4.4b), we could always get blindsided by something unexpected (e.g. H5N6, H10N3, H3N8, etc.) coming from out of left field.
Much in the way we were hit by an unexpected pandemic H1N1 swine-origin virus in 2009, and a novel coronavirus in 2020.
