The influenza virus occurs in humans, swine, wild and domestic birds and horses. Recent outbreaks in Asia have demonstrated that cats, both domestic and wild, can also become infected with the influenza virus. The influenza virus has many subtypes and certain subtypes can cause disease epidemics in people or animals. These subtypes may be different from year to year and there is some evidence that the subtypes recombine in animals, which may serve as a source of infection for people. Some subtypes may pass from animals to humans but may not pass easily between humans. Other subtypes may spread very quickly in the human population. It is not likely that the equine subtypes cause human disease.

The disease is similar in humans and animals and is characterized by the rapid onset of fever, muscle pain and cough. Birds may not show signs. Particularly virulent strains can cause more severe disease.

Prevention

• Practice personal hygiene such as covering the mouth when coughing and hand washing to reduce spread.
• Annual vaccination, especially for those with preexisting lung problems, is recommended.