The National Health Commission of China has confirmed that a 4-year-old boy in Henan Province, Central China, has been infected with the H3N8 strain of avian influenza. The patient had close contact with chickens and wild ducks raised by his family, developed a fever on April 5, and was hospitalized on April 10.
The National Health Commission of China stated that they believe the H3N8 avian influenza virus does not easily transmit to humans, and the risk of widespread outbreak is low. Close contacts of the 4-year-old boy have been tested for H3N8 and all results have been negative.
Ian Mackay, a virologist at the University of Queensland (Australia), said: “The first cases of illness need to be handled thoroughly and comprehensively, with testing of those who had contact with the patient to ensure the disease does not spread.” Mackay believes that the possibility of avian influenza virus transmission may continue to occur “as long as we live very close to virus-hosting animals.”
The rate of transmission from animals to humans is expected to increase as humans encroach further into the natural habitats of disease-carrying species. Recent studies suggest that climate change will increase the incidence of zoonotic diseases in humans.
Various strains of avian influenza have emerged in China, with some infrequent infections in humans, typically among those working with poultry. Last year, China reported the first case of human infection with the H10N3 strain of avian influenza.
China has faced several outbreaks of avian influenza in humans. (Photo: Getty Images).
Risk of Virus Mixing and Mutation
China has a large population of domesticated birds and wild birds, creating an ideal environment for avian viruses to mix and mutate. Increased surveillance of avian influenza in humans also means that more cases of infection are being detected, Reuters reported on April 26.
Previously, H3N8 had not been detected in humans, but this strain of influenza has infected birds, horses, dogs, and seals. Some studies have linked the 1889 influenza pandemic in Russia to the H3N8 virus strain, but this has never been proven.
From 2011 to 2012, a U.S. research team analyzed the H3N8 influenza virus strain associated with the deaths of seal pups in the New England area in 2011. They found that H3N8 originated from birds and had adapted to mammals, signaling a potential threat to humans and animals.
The research findings were published in July 2012 in mBio, the online journal of the American Society for Microbiology (ASM), indicating that mutations had occurred, making the influenza virus more transmissible and potentially causing severe illness.
In December 2011, scientists from the National Oceanic and Atmospheric Administration (NOAA) reported that an investigation into 162 dead seals found the H3N8 virus in all five samples studied. This was the first time this virus strain was associated with large-scale mortality in marine mammals.
Seals in the U.S. have also been victims of the H3N8 avian influenza virus. (Photo: SPL/BBC).
Severe Pneumonia and Skin Lesions
The study authors included scientists from NOAA, Columbia University, and several other organizations. Seals infected with H3N8 exhibited severe pneumonia and skin lesions, and most of them were under 6 months old.
H3N8 is commonly found in wild birds, but in 2005, researchers discovered that a strain of the virus had transmitted from horses to dogs. The disease in dogs is usually mild and not dangerous to humans.
Genetic and phylogenetic analyses of samples from seals showed that this virus is a subgroup of H3N8 avian influenza similar to the type that has infected North American waterfowl since 2002, but has adapted to mammals with mutations that make it more transmissible and pathogenic.
The research team found that the H3N8 virus in seals has the ability to bind to sialic acid receptors commonly found in the respiratory tracts of mammals. They concluded that the natural emergence of a pathogenic virus that can transmit between different mammal species poses a significant threat to wildlife and human health.
Anne Moscona, a professor of microbiology and pediatrics at Weill Cornell Medicine, who edited the report for mBio, stated that the H3N8 virus strain can transmit from one animal to another, and this characteristic makes it a potential threat to humans.
In 2017, the U.S. approved a vaccine for H3N2/H3N8 influenza for dogs after the H3N8 virus transmitted from horses to dogs. (Photo: Today’s Veterinary Business).
In 2009, the emergence of a new H1N1 virus strain (in birds, pigs, and humans) at the U.S.-Mexico border surprised global health experts. Prior to that, they had predicted that the next influenza pandemic would emerge from a country like Indonesia, where there were outbreaks of H5N1 avian influenza.
