Influenza: the disease
Influenza (commonly referred to as "flu") is a contagious viral infection that affects mainly the upper respiratory organs (nose, throat, bronchi and, occasionally, lungs).
The virus is transmitted easily from person to person via respiratory droplets produced when people cough, sneeze or spit. Close contact (less than 1 metre) is usually needed to get infected. People usually recover after a few days of what can be severe illness, but it can cause complications, including deaths especially in certain risk groups including pregnant women. Symptoms inlcude high fever, body aches, headache and severe malaise, cough, sore throat and runny nose.
Influenza tends to spread rapidly in seasonal epidemics. These flu epidemics occur yearly during autumn and winter in temperate regions and affect ~5% of adults and ~20% of children each year.
Types of influenza viruses
There are different types of flu viruses that infect different animals. Very occasionally, these animal flu viruses cause infections in humans, but as these viruses are adapted to a different species, they do not usually spread from person-to-person.
Avian Influenza or Bird Flu: Avian influenza is an infectious disease of birds caused by the A(H5N1) virus. Concern about H5N1 is that it could change to be able to pass from person-to-person and cause a pandemic. For more information see the Avian Influenza pages.
Pandemic Influenza 2009 is an animal influenza virus that emerged in the Americas in early 2009. With an ability to spread from person-to-person, the virus spread globally causing mild to severe illness. Hospitalization and deaths have occurred as a result of illness associated with this virus. For more information, see the Pandemic Influenza page.
An influenza pandemic
Pandemic influenza is a global outbreak of new human influenza. It appears to be infrequent and unpredictable, with three pandemics having occurred in the past 100 years — in 1918, 1957 and 1968. In June 2009, WHO declared an H1N1 pandemic as the virus had spread to more than 70 countries and territories. On 10 August 2010, the WHO declared that the H1N1 pandemic is over as the virus is now behaving as a seasonal influenza virus. UNICEF's response to the H1N1 pandemic is covered under pandemic influenza.