On November 23, health authorities addressed reports from the United States confirming the world’s first human case and fatality from the H5N5 avian influenza strain. H5N5 is typically an animal-to-animal virus and is not known to transmit from animals to humans. This incident marks the first documented case of H5N5 infection in a human.

According to the U.S. Centers for Disease Control, an investigation is underway. Initial findings indicate that the deceased was an elderly individual with underlying health conditions—factors that increase vulnerability to severe illness regardless of the pathogen involved. The person also had direct exposure to backyard poultry, a known risk factor. Close contacts are currently being monitored, and no additional infections have been detected.

Health officials noted that this is the first global report of H5N5 transmission to humans. There remains virtually no evidence of human-to-human transmission, similar to the behavior of the H5N1 strain. However, a virus crossing into humans suggests the possibility of viral adaptation.

Past reports of H5N5 transmission have been limited to animals, including poultry in Canada and seals in the United Kingdom, with no prior human cases. This first human infection suggests that avian influenza viruses can cross into humans when exposed to sick or dead birds without proper protection.

H5N5 and H5N1 differ in their N protein type, which exists in various subtypes. However, in terms of outbreak patterns, prevention measures, and treatment approaches, the two strains are similar. Clinical data on H5N5 in humans remain limited since no previous human infections have been recorded.

Because this case involved an elderly person with underlying conditions, experts caution that it is too early to determine how severe H5N5 infection would be in the general population—or in children—should transmission occur. Continuous monitoring is required.

Regarding H5N1, multiple sublineages exist, including those circulating in the United States in the past year, which were largely linked to livestock exposure and generally caused mild symptoms. One fatality was previously reported, also involving an elderly individual with chronic illnesses.

In Cambodia, certain H5N1 sublineages have shown higher severity. Recent reports confirmed another child’s death in Phnom Penh, with the case linked to exposure to sick or dead poultry. Authorities emphasize that avian influenza of any strain poses the greatest danger to high-risk groups, such as the elderly or those with chronic conditions.

Health officials also confirmed that Thailand has not reported any human infections to date. As colder weather increases the incidence of avian influenza and other respiratory diseases, extra caution is advised, especially for those working with poultry, wild birds, or open farms.

Any unexplained illness or death in animals should be reported immediately to local livestock authorities. Anyone who has had contact with poultry—or even mammals—should use protective gear including masks, gloves, or protective gowns when handling carcasses. Those who develop fever, cough, or respiratory symptoms within two weeks of such exposure should inform their healthcare providers of this history.

Seasonal influenza vaccination is also recommended, as it not only prevents typical flu illness but helps reduce the risk of genetic reassortment should influenza and avian viruses infect the same person, which could potentially create a more transmissible strain.

 

Source: www.thaihealth.or.th