Source: World Health Organization + www.flu.gov
What is flu?
Flu is a viral infection that affects mainly the nose, throat, bronchi and, occasionally, lungs. Infection usually lasts for about a week, and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive cough, sore throat and rhinitis.
The virus is transmitted easily from person to person via droplets and small particles produced when infected people cough or sneeze. Flu tends to spread rapidly in seasonal epidemics.
Most infected people recover within one to two weeks without requiring medical treatment. However, in the very young, the elderly, and those with other serious medical conditions, infection can lead to severe complications of the underlying condition, pneumonia and death.
Pandemic (H1N1) 2009 is a new Flu virus that has never circulated among humans before. After outbreaks in North America early in 2009, the virus spread rapidly around the world. Pandemic Flu is transmitted like seasonal Flu but people have virtually no immunity to it. Mitigating its effects is a public health priority.
Some groups are more likely to have complications from the seasonal flu. These include:
- those age 65 and older
- children younger than 2 years old
- people of any age who have chronic medical conditions (e.g. diabetes, asthma, congestive heart failure, lung disease)
Complications from the flu can include:
- bacterial pneumonia
- ear or sinus infections
- worsening of chronic medical conditions
Different types of flu
1. Flu (Seasonal)
- Flu is an acute viral infection that spreads easily from person to person.
- Flu circulates worldwide and can affect anybody in any age group.
- Flu causes annual epidemics that peak during winter in temperate regions.
- Flu is a serious public health problem that causes severe illnesses and deaths for higher risk populations.
- An epidemic can take an economic toll through lost workforce productivity, and strain health services.
- Vaccination is the most effective way to prevent infection.
Seasonal Flu is an acute viral infection caused by a Flu virus.
There are three types of seasonal Flu – A, B and C. Type A Flu viruses are further typed into subtypes according to different kinds and combinations of virus surface proteins. Among many subtypes of Flu A viruses, currently Flu A (H1N1) and A(H3N2) subtypes are circulating among humans. Flu viruses circulate in every part of the world. Type C Flu cases occur much less frequently than A and B. That is why only Flu A and B viruses are included in seasonal Flu vaccines.
Signs and symptoms
Seasonal Flu is characterized by a sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and runny nose. Most people recover from fever and other symptoms within a week without requiring medical attention. But Flu can cause severe illness or death in people at high risk (see below). The time from infection to illness, known as the incubation period, is about two days.
Flu Symptoms and Cold vs. Flu
- fever (usually high)
- tiredness (can be extreme)
- dry cough
- sore throat
- runny or stuffy nose
- muscle aches
These symptoms may occur, but are more likely in children than adults:
Note that these additional symptoms may also be a sign of the H1N1 flu.
Who is at risk?
Yearly Flu epidemics can seriously affect all age groups, but the highest risk of complications occur among children younger than age two, adults age 65 or older, and people of any age with certain medical conditions, such as chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes), or weakened immune systems.
Seasonal Flu spreads easily and can sweep through schools, nursing homes or businesses and towns. When an infected person coughs, infected droplets get into the air and another person can breath them in and be exposed. The virus can also be spread by hands infected with the virus. To prevent transmission, people should cover their mouth and nose with a tissue when coughing, and wash their hands regularly.
Antiviral drugs for Flu are available in some countries and effectively prevent and treat the illness. There are two classes of such medicines, 1) adamantanes (amantadine and remantadine), and 2) inhibitors of Flu neuraminidase (oseltamivir and zanamivir). Some Flu viruses develop resistance to the antiviral medicines, limiting the effectiveness of treatment. WHO monitors antiviral susceptibility in the circulating Flu viruses.