What to know about the first human case of H5N2 bird flu

Should we be concerned about a new strain of bird flu?

Recently, the World Health Organization announced the first confirmed case of the H5N2 type of bird flu in a 59-year-old man from Mexico who passed away in April. This development has increased concerns about the potential spread of bird flu among humans, especially because the man had no known contact with poultry or other animals, according to the WHO.

It’s important to note that H5N2 is a distinct strain from the H5N1 bird flu virus that has been affecting dairy cow herds in the United States. The H5N1 virus has caused mild infections in three farm workers.

So, what exactly is H5N2, and does it pose a significant health risk to humans?

H5N2 is classified as one of many avian influenza viruses. While it is a cause for concern, it is not yet clear whether it poses a significant health risk to humans. Further research and monitoring are needed to determine its potential for human-to-human transmission and its overall impact on public health.

As scientists and health officials continue to investigate and monitor the situation, it is crucial for individuals to stay informed and take necessary precautions to minimize their risk of exposure to bird flu viruses.
According to Dr. Troy Sutton, an assistant professor of veterinary and biomedical sciences at Penn State, it is not surprising to find exposure to the H5 virus in Mexico. H5 viruses have been present in poultry and wild birds in Mexico since the mid-1990s. However, unlike other avian influenza strains like H1 and H3 viruses that have caused outbreaks in humans, H5 viruses rarely infect humans.

These viruses are categorized based on two types of proteins on their surfaces: hemagglutinin (H) and neuraminidase (N). The H protein allows the virus to infect cells, while the N protein helps the virus spread. There are many possible combinations of H and N proteins.

H5N2 belongs to the H5 family of bird flu viruses, which primarily infect wild birds. According to the Centers for Disease Control and Prevention, there are a total of nine known subtypes of H5 viruses.
H5N1, which was discovered in dairy cows in the U.S. in March, also belongs to this family. It is commonly associated with highly contagious strains of H5 viruses known as the “Goose Guangdong lineage” that have caused numerous outbreaks in poultry over the past 20 years and sporadic infections in humans, explained Sutton.

According to the CDC, H5N1 has infected individuals in 23 countries since 1997, resulting in severe pneumonia and a 50% fatality rate.

Sutton described the H5N2 and H5N1 viruses as separate lineages with their own distinct history and impact on disease.

Should people be worried?

The patient in Mexico had been bedridden for several weeks before experiencing symptoms.

On April 17, the individual developed fever, nausea, diarrhea, shortness of breath, and general discomfort, as reported by the WHO. A week later, on April 24, they were admitted to the hospital and passed away on the same day.
According to Sutton, it is worth noting that the man had multiple pre-existing medical conditions, which likely worsened his infection.

Sutton explained, “The person may have already been quite sick. This changes the situation a bit more compared to, let’s say, a healthy farm worker getting infected.”

The World Health Organization (WHO) confirmed that no other cases were reported during their investigation. Out of the 17 individuals who had contact with the patient at the hospital where he passed away, only one reported having a runny nose.

However, experts are still unsure of how the man contracted the virus since he had no exposure to poultry or other animals. If he was infected by another human, it suggests that there may be additional unidentified cases.

“It is concerning that a new subtype of the virus has infected a human,” Sutton expressed.
According to Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota, human-to-human transmission is unlikely in the case of the H5N2 virus. He believes that both individuals likely contracted the virus from the same source.

Osterholm explains that the H5N2 virus is classified as a low pathogenic virus, which means it is less likely to cause severe illness. He distinguishes between high pathogenic and low pathogenic viruses, noting that the former has genetic changes that make it more likely to cause serious illness. On the other hand, the low pathogenic virus can easily infect various animal species without causing noticeable symptoms.

One of the main concerns for scientists is whether the H5N2 virus has undergone any mutations that have made it more transmissible to humans. Dr. Paul Offit, an infectious disease expert and the director of the Vaccine Education Center at Children’s Hospital of Philadelphia, highlights this as a key question among experts.
According to experts, H5 viruses have difficulty infecting humans because they target different cell receptors in birds compared to humans. This is why people usually become infected with H5 viruses through direct contact with birds and poultry, rather than from other humans. H5N1, although it can cause infections in humans, has never caused widespread human-to-human transmission. Regarding the H5N2 virus, experts believe that the fact that it is different from H5N1 does not necessarily make it more likely to cause a pandemic. If the virus cannot replicate well in the upper respiratory tract, it will not easily spread from human to human. Further genetic sequencing of the H5N2 virus is still needed to determine whether it poses a risk to humans.
“It is difficult to make definitive conclusions without having that information,” the editor explained.

According to Osterholm, the H5N1 virus is the primary concern that requires intense attention.

The U.S. Department of Agriculture reported that the H5N1 virus has rapidly spread among dairy cows, infecting 84 herds in nine states. This raises concerns about the potential for the virus to mutate and infect humans.

This article was initially published on NBCNews.com.

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