Bird flu, or avian flu, is an infectious viral illness that affects mainly birds.
Most bird flu viruses don't affect humans, but some strains — particularly H5N1 and H7N9 — can in rare cases cause serious infections in people.
Bird flu is transmitted to humans through direct or indirect exposure to live or dead birds infected with the virus, such as by working with poultry (farming) or consuming raw or undercooked meat, blood, or eggs.

Bird Flu Symptoms

According to the World Health Organization (WHO), the bird flu viruses H5N1 and H7N9 produce symptoms 2 to 3 days and 2 to 8 days after exposure, respectively.
In some cases, the viruses cause only conjunctivitis (pink eye), but they most often cause flu-like symptoms, including:
  • Fever greater than 100.4 degrees F (38 degrees C)
  • Cough
  • Sore throat
  • Diarrhea
  • Vomiting
  • Abdominal pain
  • Chest pain
  • Bleeding from the nose and gums
  • Headache
In many cases, the virus spreads to the lower respiratory tract, causing pneumonia, which can result in:
  • Difficulty breathing
  • Hoarse voice
  • Crackling sound while inhaling
  • Mucus or blood in cough
Bird flu may also cause other infections and complications, such as:
  • Hypoxemia (low blood oxygen)
  • Respiratory failure
  • Multiple organ dysfunction and failure
  • Sepsis (blood infection)
  • Secondary bacterial and fungal infections, especially bacterial pneumonia

Bird Flu Treatment

Bird flu in humans is typically treated with one of a few antiviral medications, including Tamiflu (oseltamivir), peramivir, and zanamivir, which reduce the viruses' ability to replicate.
Oseltamivir is in pill form, whereas peramivir is an intravenous (IV) medication, and zanamivir is inhaled as a powder.
However, some strains of the viruses H5N1 and H7N9 have shown resistance to antiviral drugs, according to the Centers for Disease Control and Prevention (CDC).
In 2007, the CDC approved a vaccine for H5N1. But this vaccine is not commercially available to the public, and is instead being stockpiled by the CDC to be used in the event of a national bird flu emergency.
In May 2015, researchers at Kansas State University announced the development of H5N1 and H7N9 vaccines for birds, according to the Journal of Virology.

Bird Flu Outbreaks

Bird flu virus H5N1 first infected humans in 1997 during a poultry outbreak in China, and became widespread in 2003 and 2004.
In total, it has caused more than 700 infections across 15 countries, with a mortality rate of about 60 percent, according to the CDC.
Indonesia, Vietnam, and Egypt have had the highest numbers of human H5N1 infections, and the United States has had none.
In 2014, Canada reported the first human infection of H5N1 in the Americas, which occurred in a person who recently returned from China.
Bird flu virus H7N9 first infected three people in China in 2013, according to the WHO.
Of the now 571 laboratory-confirmed human cases of H7N9, 568 cases occurred within China, one occurred in a Chinese traveler to Malaysia, and two occurred in people in Canada who had just returned from China.
Although the United States has not had any human cases of H7N9 or H5N1, it has had a few other types of bird flu infections in humans.
For instance, in 2002, a person culling poultry in Virginia developed a H7N2 infection. In 2003, a man in New York also contracted the H7N2 virus.