Recently, highly pathogenic (H5N1) avian influenza (AI) has been spreading among migratory birds, chickens, ducks, and cattle in the United States. In this context, the first reported case of a patient infected with this virus has died. Fears of a pandemic in the U.S. are expected to increase.
The U.S. Department of Health announced on the 6th (local time) that a patient who had been hospitalized in Louisiana with H5N1 had died.
The patient, an elderly individual over 65 years old, had underlying health conditions. After being exposed to backyard chickens and wild birds last month, the person became infected with the virus and was in danger due to severe respiratory illness. The U.S. Department of Health reported that no additional infection cases were found among those who had contact with the deceased.
As the H5N1 virus spreads from poultry and wild birds to humans in the United States, fears are growing. The H5N1 virus is a variant of the Type A influenza virus, which carries the highest risk of human infection. It received the name H5N1 because the proteins hemagglutinin (HA) and neuraminidase (NA) on its surface are of subtypes 5 and 1, respectively. HA plays a key role in allowing the virus to attach to human respiratory cells, while NA enables the virus to escape after replication.
So far, a total of 67 cases of human infection with H5N1 have been recorded in the United States, of which all but one case occurred during the past year. Since 2003, more than 450 lives have been lost worldwide, but this is the first death in the U.S. caused by this virus.
Analysis of the viral genetic sequence from the deceased individual revealed that it was a different type of virus than the H5N1 currently circulating among U.S. cattle. The cattle virus is genotype B3.13, but the virus that infected the deceased was a D1.1 genotype virus circulating among wild birds. This is of the same type as the infecting virus that left a Canadian teenager in critical condition last November.
Experts express particular concern about this D1.1 virus. Richard Webby, director of the World Health Organization (WHO) Center for Animal Influenza Ecology Research at St. Jude Children's Research Hospital, noted, "The D1.1 virus has a different neuraminidase gene than the virus from cattle, and such changes could induce mutations in hemagglutinin."
Webby further stated, "I have been studying the lineage of this virus for 25 years, and it is the most dangerous form we have seen to date. It is not surprising that this virus caused a severe infection."
Scientists analyzed that if both proteins responsible for creating H5N1 undergo mutations, the avian influenza virus could bind to and invade human lung cells. If the H5N1 virus acquires the ability to easily infect humans through genetic mutation, it could lead to a second pandemic.
Researchers at St. Jude Children's Research Hospital, which has been conducting a bird droppings analysis project for 40 years with support from the National Institutes of Health (NIH), recently discovered D1.1 in a flock of waterfowl over the past two months. They report it as a recombinant virus that emerged after two viruses simultaneously infected the same animal and exchanged genetic material. The researchers also confirmed that the D1.1 genotype virus is linked to the migratory pathway that runs from central Canada down to the Gulf of Mexico along the Mississippi River.