Sat Nov 09 17:30:00 UTC 2024: ## Novel H5N1 Reassortment Virus Sparks Concerns in Cambodia

**Phnom Penh, Cambodia -** Cambodia has witnessed a concerning surge in H5N1 avian influenza cases in humans, with a total of 16 cases reported between February 2023 and August 2024. While the initial cases were attributed to the A/H5 clade 2.3.2.1c virus, a new strain, a reassortant virus, has emerged, causing an additional 14 cases and three deaths since October 2023.

The reassortment event is a result of mixing genetic material from the 2.3.2.1c clade, prevalent in Southeast Asia, with the 2.3.4.4b clade, which has spread globally. This novel strain has led to a direct poultry-to-human transmission, with no evidence of human-to-human spread reported so far.

A team from the Pasteur Institute in Cambodia, in a preprint published on November 5, analyzed the genetic makeup of the reassortant virus, highlighting the need for enhanced surveillance. The study found that the virus responsible for the recent surge in cases is closely related to a strain detected in poultry and wild birds in Vietnam and Laos.

While the exact origins of this reassortment remain unclear, researchers believe the high-density poultry farming, wild bird migration, and cross-border poultry trade in the region have played a role. Notably, the 2.3.2.1c clade is no longer circulating in poultry in Cambodia, replaced by the novel reassortant virus.

The reassortant virus exhibits certain mutations associated with enhanced capacity for mammalian infection, raising concerns about its potential zoonotic risk. The presence of the PB2 627K mutation, linked to increased mammalian adaptation and airborne transmission in ferrets, further underlines the need for close monitoring of this strain.

Dr. Jurre Y. Siegers, the lead author of the preprint, emphasizes the importance of sustained surveillance of avian influenza in poultry and wild birds, especially in Southeast Asia. Alongside this, awareness programs aimed at reducing human exposure to infected poultry and promoting safe handling practices are crucial to mitigate the risk of further spread.

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