H5N1 is not the only version of avian flu we have to worry about. On March 17, veterinarians reported that a highly pathogenic strain of H7N9 bird flu, a different strain from the H5N1 flu that has been circulating in cows and poultry since last year, was recently detected in a Mississippi poultry farm.

On March 17, the World Organization for Animal Health (OIE) released its report on the H7N9 outbreak, based on data provided to it by the U.S. Department of Agriculture and local authorities. This is the first outbreak of H7N9 in poultry observed in the United States in nearly a decade.

Highly pathogenic avian influenza (HPAI) viruses are a serious public health concern. These viruses spread rapidly among wild birds and poultry, often causing widespread deaths (which is why they are called highly pathogenic). They can also spread to other animal species, including humans. The fear is that one such strain will pick up the wrong combination of mutations that will allow it to spread widely and cause severe disease in humans - the perfect recipe for a deadly pandemic.

The best-known subtype of HPAI circulating today is H5N1. Since early 2024, H5N1 has been causing outbreaks in cows across the country, sometimes crossing into other mammals such as cats and humans. But other types of HPAI are always spreading, including H7N9.

This particular subtype of bird flu was first detected in China in 2013. One of the reasons why H7N9 is of concern is its deadly danger when spread to humans. According to the World Health Organization, most reported cases of H7N9 in humans have resulted in severe illness. Of the 1,568 cases of H7N9 documented globally since 2013, 616 people have died - a 39% fatality rate.

The last known U.S. outbreak of H7N9 in poultry occurred in 2017. But in early March, it made an unwelcome return to a farm in Knoxby, Mississippi. The virus was detected in a flock of nearly 50,000 commercial broiler chickens, according to the WHO. Genetic testing confirming the identity of the strain was completed late last week.

"The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS), in conjunction with state animal and wildlife health officials, are conducting a comprehensive epidemiological investigation and enhanced surveillance in response to the discovery," the WOZW said of the outbreak.

As is standard procedure to contain these highly contagious infections, the population of exposed chickens on the farm is being destroyed. So it is possible that this outbreak will remain an isolated case. But the overall threat of avian influenza is growing. According to the organisation's latest situation report, published last month, there have already been more outbreaks of HPAI strains in poultry globally in the first 5 months of the current seasonal wave (which started in October 2024) than there were total outbreaks in the entire previous season (October 2023 to September 2024).

These outbreaks have contributed in large part to the sharp rise in the price of eggs, although it is already beginning to decline, according to the USDA (US Department of Agriculture).

However, it is uncertain going forward how effective health officials will be in containing H5N1 and other strains of avian flu in the US. | BGNES