Bird flu, or avian influenza, is a viral infection primarily spread among birds. The most common strain is H5N1, which poses a significant threat to birds but rarely spreads to humans. However, a major outbreak occurred in 2014, with limited human-to-human transmission observed among individuals with close contact, such as a mother caring for her sick infant.

Migrating waterfowl, particularly wild ducks, are natural carriers of bird flu viruses. Scientists believe that the infection can spread from wild birds to domestic poultry.

Symptoms of Bird Flu

Bird flu symptoms in humans can vary but often start with flu-like symptoms, including fever, cough, sore throat, and muscle aches. The condition may worsen to include:

• Gut problems: Nausea, abdominal pain, diarrhea, and vomiting.
• Breathing problems: Shortness of breath, severe respiratory distress or failure, pneumonia, and other respiratory diseases.
• Brain or nervous system changes: Changes in behavior, thinking, or organ function. In severe cases, seizures may occur.

In 2005, researchers in Vietnam reported that the virus could infect the brains and digestive tracts of humans, as seen in two fatal cases in children. This indicates that bird flu can manifest differently from typical flu.

Scientists have identified over a dozen strains of bird flu, with H5N1 being particularly deadly to humans, causing 456 deaths since 2003 according to the World Health Organization.

How Do Humans Get Bird Flu?

Humans can contract bird flu through close contact with infected birds or their droppings. During the 2014 outbreak, people got infected by cleaning or plucking infected birds, inhaling aerosolized materials in live bird markets, or swimming in contaminated water. Handling fighting cocks has also led to infections. However, eating fully cooked chicken or eggs does not transmit the virus.

There have been rare cases of human-to-human transmission, often involving close personal contact. For instance, in 2006, bird flu spread within a family in Indonesia, resulting in seven deaths. The exact transmission method remains unclear, but shared contact with infected birds and genetic susceptibility are likely factors.

Bird Flu in the U.S.

Various bird flu strains occasionally appear in U.S. poultry. When detected, affected flocks are culled to prevent spread. In 2004, an H5N2 outbreak occurred in Texas but was eradicated without human infections.

Types of Bird Flu

Avian influenza A viruses are categorized into:

• Highly pathogenic avian influenza (HPAI): Causes severe illness and high mortality in chickens.
• Low pathogenicity avian influenza (LPAI): Causes milder illness and lower mortality in chickens but can still spread rapidly and cause serious illness in humans.

Viruses evolve over time, leading to different strains. Human infections, though rare, are most often from H5, H7, and H9 strains, with occasional cases from H10N8, H10N7, and H6N8.

Bird Flu Vaccine

A vaccine to prevent human infection with H5N1 was approved by the FDA in 2007 but is not commercially available. The U.S. government has stockpiled the vaccine for potential distribution by public health officials.

Treatment for Bird Flu

Flu drugs such as oseltamivir (Tamiflu), peramivir (Rapivab), and zanamivir (Relenza) may help treat bird flu in humans. These medications are most effective when administered soon after symptoms appear, although more research is needed to confirm their efficacy.