Bird flu, or avian flu, is an infectious form of influenza that spreads among birds and in rare cases can affect humans. There are 4 strains that have caused concern in recent years:
H5N1 (since 1997)
H7N9 (since 2013)
H5N6 (since 2014)
H5N8 (since 2016)
Symptoms include a very high temperature, aching muscles, headache or a cough or shortness of breath. For medical advice, contact the NHS.