Health and Me

Itisha Arya

Bird Flu In US: How Is The New H5N5 Strain Different From H5N1?

h5n5 and h5n1 bird flu strain

As bird flu continues to trouble several countries, health officials in the United States have reported the first known human case of the H5N5 subtype of avian influenza. The Washington State Department of Health announced on November 14, 2025, that the virus was found in a resident of Grays Harbor County. 

The patient, an older adult with existing medical issues, is currently in the hospital. Authorities noted that the individual kept poultry at home that had contact with wild birds, which is believed to be the likely source of the infection, though the investigation is still underway. Since H5N5 is newly identified in humans, many are asking whether it differs from the earlier <span>H5N1 strain</span>.

H5N1 is a highly pathogenic form of avian influenza that mainly affects birds but can also infect mammals, including humans. It can lead to severe illness in people and has a high fatality rate, though it rarely spreads from one person to another, as per the <span>World Health Organization</span>. The virus has moved across continents in wild and farmed birds and has recently been found in dairy cattle and several other mammals.

<h2>What Is The New <span rel="noindex">H5N5 Strain</span>?</h2>

The “new” H5N1 strain refers to the 2.3.4.4b clade of highly pathogenic avian influenza (HPAI), which has caused a widespread animal outbreak since appearing in 2020. This version is a newer genetic branch of H5N1 and has swept through wild birds, poultry farms and an increasing range of mammals, including dairy herds in the United States. At present, the patient infected in the U.S. has been diagnosed with the newer H5N5 subtype.

<h2><span rel="noindex">How Is H5N5 Different From H5N1</span>?</h2>

According to the <span>CDC</span>, both H5N5 and H5N1 fall under the <span>avian influenza family</span>, with the main distinction being the type of neuraminidase (N) protein on the virus surface. H5N5 contains the N5 protein, while H5N1 carries the N1 protein. Although this genetic change can influence viral features, their overall pattern of illness and symptoms is expected to be much the same, particularly in birds and livestock.

The genetic structure is the only difference, with H5N1 strain containing a subtype of influenza A with a segmented genome while the other has a new reassortant virus formed from several subtypes, possibly including H5N1, as per National Institute of Health.

<h2>Is A Vaccine Available For The H5N1 Bird Flu Strain?</h2>

Vaccines for bird flu do exist, but they are not intended for general public use and are not easily available for everyday protection. Some vaccines have been created and stored for possible deployment in people at higher risk, such as poultry workers and farm staff, and they are also used in animals like chickens to help manage outbreaks. The United States and several other countries have stockpiled H5N1-specific vaccines that could be rolled out if the threat to humans grows. A few nations, including Finland, are already offering them to certain high-risk groups. At the moment, there is no advice for the wider public to take a bird flu vaccine, as there is no sustained human-to-human spread and no mass-market human vaccine in use.

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As bird flu continues to trouble several countries, health officials in the United States have reported the first known human case of the H5N5 subtype of avian influenza. The Washington State Department of Health announced on November 14, 2025, that the virus was found in a resident of Grays Harbor County. The patient, an older adult with existing medical issues, is currently in the hospital. Authorities noted that the individual kept poultry at home that had contact with wild birds, which is believed to be the likely source of the infection, though the investigation is still underway. Since H5N5 is newly identified in humans, many are asking whether it differs from the earlier H5N1 strain.What Is the H5N1 Strain?H5N1 is a highly pathogenic form of avian influenza that mainly affects birds but can also infect mammals, including humans. It can lead to severe illness in people and has a high fatality rate, though it rarely spreads from one person to another, as per the World Health Organization. The virus has moved across continents in wild and farmed birds and has recently been found in dairy cattle and several other mammals.What Is The New H5N5 Strain?The “new” H5N1 strain refers to the 2.3.4.4b clade of highly pathogenic avian influenza (HPAI), which has caused a widespread animal outbreak since appearing in 2020. This version is a newer genetic branch of H5N1 and has swept through wild birds, poultry farms and an increasing range of mammals, including dairy herds in the United States. At present, the patient infected in the U.S. has been diagnosed with the newer H5N5 subtype.How Is H5N5 Different From H5N1?According to the CDC, both H5N5 and H5N1 fall under the avian influenza family, with the main distinction being the type of neuraminidase (N) protein on the virus surface. H5N5 contains the N5 protein, while H5N1 carries the N1 protein. Although this genetic change can influence viral features, their overall pattern of illness and symptoms is expected to be much the same, particularly in birds and livestock.The genetic structure is the only difference, with H5N1 strain containing a subtype of influenza A with a segmented genome while the other has a new reassortant virus formed from several subtypes, possibly including H5N1, as per National Institute of Health.Is A Vaccine Available For The H5N1 Bird Flu Strain?Vaccines for bird flu do exist, but they are not intended for general public use and are not easily available for everyday protection. Some vaccines have been created and stored for possible deployment in people at higher risk, such as poultry workers and farm staff, and they are also used in animals like chickens to help manage outbreaks. The United States and several other countries have stockpiled H5N1-specific vaccines that could be rolled out if the threat to humans grows. A few nations, including Finland, are already offering them to certain high-risk groups. At the moment, there is no advice for the wider public to take a bird flu vaccine, as there is no sustained human-to-human spread and no mass-market human vaccine in use.