🤒 First case of H5N5 avian flu detected in humans

The emergence of a new viral subtype in humans always represents a significant event for global epidemiological surveillance. In Washington State, the confirmation of an H5N5 virus infection in a hospitalized patient constitutes an unprecedented milestone. This strain, previously mainly observed in the animal kingdom, has crossed the species barrier, drawing researchers' attention to its possible implications. The focus is now on the properties of this pathogen and the actual conditions of its transmission.

This situation occurs during a period of intense avian flu circulation. For several years, different strains have been subject to enhanced monitoring due to their consequences on wildlife and livestock. The discovery of this human case, although isolated for now, highlights the usefulness of health surveillance systems. It encourages a thorough examination of the relationships between human activities, wildlife, and the emergence of infectious diseases.

The first human case of H5N5

The person affected by this infection is an elderly resident of Grays Harbor County with serious medical history. Their condition required hospitalization in early November, where medical tests initially identified an H5-type virus. Advanced genetic analyses conducted by health authorities subsequently led to the characterization of the H5N5 subtype, an occurrence never documented in humans. The patient kept several domestic poultry at home, forming an exposure scenario considered most likely.

The epidemiological investigation conducted by the Washington State Department of Health attempts to trace the precise transmission pathway. The patient's domestic poultry had been exposed to wild birds, which represent the natural reservoir of these viruses. Although this lead is favored, research continues to exclude any other origin and understand the exact conditions that allowed this cross-species transmission. This approach is essential to assess the threats of similar subsequent transmissions.

The official announcement of this case occurred on November 14, in accordance with usual protocols for reporting emerging infectious diseases. Health authorities, particularly the Centers for Disease Control and Prevention (CDC), indicate that the threat level for the general population is currently considered moderate. No other cases associated with this subtype have been reported at this stage, and no human-to-human spread has been observed, which represents an encouraging factor in assessing the situation.

A virus in the influenza ecosystem

The H5N5 virus belongs to the large family of type A influenza, defined by their two surface proteins: hemagglutinin (H) and neuraminidase (N). Its proximity to the H5N1 subtype, already well-identified and responsible for the majority of recent human infections, is evident. They share the same H5 protein, which largely determines their ability to infect cells. The distinction lies in the N5 protein, whose specific impact on viral behavior is not yet fully understood by scientists.

According to initial observations communicated by specialists like Richard Webby of St. Jude Hospital, cited by the Associated Press, H5N5 appears to have characteristics very similar to those of H5N1. The symptoms observed in the patient - including high fever and respiratory discomfort - are analogous to those caused by other severe avian flus. This resemblance indicates that established medical care protocols and prevention measures remain useful against this new pathogen.

The persistent circulation of these viruses within animal populations allows pathogens to exchange and combine their genetic material. As indicated by the World Organisation for Animal Health, this genetic diversity can lead to the emergence of new variants. The identification of H5N5 in humans thus serves as a signal regarding the permanent adaptive capacity of this type of virus. It justifies maintaining rigorous observation within animal reservoirs to predict possible modifications in their ability to transmit.