SYLLABUS
GS-2: Issues relating to the development and management of Social Sector/Services relating to Health.
Context: Recently, a resident of the United States has died from H5N5 avian influenza, marking the first documented human infection and fatality from this subtype virus.
More on the News
- H5N5 is normally found in wild birds, and it often spreads to domestic poultry, but it has never infected a human before this case.
- Health authorities confirmed that the H5N5 strain is different from the widely circulating H5N1 strain responsible for poultry outbreaks.
- Officials stated that the risk to the general public remains low and there is no sign of human-to-human transmission.
- Public health experts advise poultry owners to separate domestic birds from wild birds to reduce infection risk and to use protective gear while handling poultry or cleaning coops.
H5N5 Bird Flu
- Bird flu (avian influenza) is an infection from a type of influenza (flu) virus that usually spreads in birds and other animals. Sometimes, humans can get bird flu from infected animals.
- The H5N5 Bird Flu is classified as a highly pathogenic avian influenza strain, and it can cause severe disease in poultry.
- Bird flu viruses are classified as either “high pathogenicity” or “low pathogenicity” based on the severity of symptoms they cause in poultry.
- Influenza viruses are categorised based on two surface proteins called haemagglutinin and neuraminidase. H5N1 and H5N5 share the H5 subtype but differ in the neuraminidase subtype.
Symptoms of H5N5 Avian Influenza in Humans
- Although the recent case is the first documented human infection, the symptoms observed are consistent with severe avian influenza. Reported and likely symptoms include:
- High fever
- Severe respiratory distress, including shortness of breath
- Cough (often persistent and worsening)
- Fatigue and weakness
- Headache and muscle pain
- Confusion or altered mental status (noted in the U.S. case)
- Pneumonia, which may rapidly progress
- Gastrointestinal symptoms (less common, but possible in avian flu infections)
- Rapid clinical deterioration, especially in older adults or those with underlying health conditions
- These symptoms resemble those caused by other highly pathogenic avian influenza viruses such as H5N1, but the severity depends on age, immunity, and comorbidities.
Key Distinctions between H5N1 and H5N5
| Feature | H5N1 | H5N5 |
| Neuraminidase (N) Protein | N1 subtype | N5 subtype |
| Hemagglutinin (H) Protein | H5 subtype (same as H5N5) | H5 subtype (same as H5N1) |
| Genetic Origin | A long-circulating and widespread genetic lineage that has caused global outbreaks in animals since 2020. | It is often a novel reassortant virus, meaning it likely formed when an H5N1 virus exchanged genetic segments with another influenza virus type in a co-infected host, such as a duck. |
| Disease Severity in Animals | Highly pathogenic, causing high mortality in poultry and affecting a wide range of mammals. | Also highly pathogenic in birds. The overall pattern of illness and symptoms in birds and livestock is expected to be similar to H5N1. |
| Human Cases | Has caused numerous human infections globally since the late 1990s, with a high mortality rate in early cases. Many recent cases in the U.S. linked to dairy farms have been mild. | Human cases are much rarer. The first human case and death was recently recorded in the U.S. in November 2025. |