How dangerous is H3N8 bird flu to humans?

China's National Health Commission has just confirmed that a 4-year-old boy from Henan province, central China, has been infected with the H3N8 strain of bird flu. The patient had close contact with chickens and mallards raised by his family, then had a fever on April 5 and was hospitalized on April 10.

The National Health Commission of China stated that they believe that the H3N8 avian influenza virus is not yet capable of infecting humans easily, and the risk of the disease spreading on a large scale is low. Close contacts of the 4-year-old boy were tested for H3N8 and all tested negative.

Mr. Ian Mackay, a virologist at the University of Queensland (Australia), said: 'The first cases of the disease need to be treated thoroughly and comprehensively with testing of those who have been in contact with the patient to make sure. make sure the disease doesn't spread'. Mr Mackay said that bird flu virus transmission could continue to happen "while we live very close to the virus hosts".

The rate of animal-to-human transmission is predicted to increase as humans encroach further into the natural habitats of disease-carrying species. Recent studies suggest that climate change will increase the odds of humans contracting animal diseases.

Various strains of avian influenza have emerged in China, and some have sporadically infect humans, often those who work with poultry. Last year, China reported its first human case of H10N3 bird flu.

China has faced several outbreaks of avian influenza in humans.

Risk of viruses mixing and mutating

China has many species of domestic and wild birds in large numbers, creating an ideal environment for avian viruses to mix and mutate. Increased surveillance of human bird flu also means more infections are 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. Several studies have linked the 1889 flu pandemic in Russia to the H3N8 virus strain, but this has never been proven.

From 2011 to 2012, a US research team analyzed the H3N8 influenza virus strain that was associated with the deaths of seal cubs in the New England area in 2011. They found that H3N8 originated in poultry. , birds and have adapted to mammals, signaling a possible threat to humans and animals.

The results of the study, published in July 2012 in mBio, the online journal of the American Society for Microbiology (ASM), found that a mutation has occurred that makes the flu virus more contagious and can cause illness. heavy.

In December 2011, scientists from the US National Oceanic and Atmospheric Administration (NOAA) announced that an investigation of 162 dead seals had detected the H3N8 virus in all 5 samples. studied. For the first time, this virus strain is associated with large-scale mortality in marine mammals.

Seals in the US have also been victims of the H3N8 bird flu virus.

Severe pneumonia, skin damage

The study authors include scientists from NOAA, Columbia University, and several other institutions. Seals infected with H3N8 developed severe pneumonia and skin lesions, and most of them were under 6 months of age.

H3N8 is commonly found in wild birds, but in 2005, researchers discovered that a strain of the virus had spread from horses to dogs. Diseases in dogs are usually mild and pose no danger to humans.

Genetic and phylogenetic analysis of seal samples revealed that the virus is a subtype of avian influenza H3N8 similar to that which has infected North American waterfowl since 2002, but has adapted to animals. mammals with mutations that make it more contagious and disease-causing.

The team found that the H3N8 virus in seals has the ability to bind to sialic acid receptors commonly found in the mammalian respiratory tract. They concluded that it was the natural occurrence of a disease-causing virus that could be transmitted between mammalian species, and that a species could infect multiple influenza subtypes. This is considered a significant threat to wildlife and human health.

Anne Moscona, a professor of microbiology and pediatrics at Weill Cornell Medical College who edited the report for mBio, said that the H3N8 virus strain can be transmitted from one animal to another, and the characteristics are This makes it a potential threat to humans.

In 2017, the US licensed the H3N2/H3N8 flu vaccine for dogs after the H3N8 virus was transmitted from horses to dogs.

In 2009, the emergence of a new strain of virus H1N1 (in birds, pigs and humans) at the US-Mexico border surprised global health experts. Before that, they predicted the next flu pandemic would emerge from a country like Indonesia - where the H5N1 bird flu was found.