What is Flu? What is Influenza? What are the Symptoms of Flu?

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Main Category: Flu / Cold / SARS
Also Included In: Respiratory / Asthma;  Infectious Diseases / Bacteria / Viruses
Article Date: 03 Mar 2009 - 0:00 PDT

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Influenza, or flu, is a respiratory illness that is caused by a virus. Flu is highly contagious and is usually spread by the coughs and sneezes of a person who is infected. You can also catch flu from an infected person if you touch them (e.g. shaking hands). Adults are contagious one day before getting symptoms and up to 7 days after becoming ill. This means that you can spread the influenza virus before you even know you are infected. A flu epidemic, when a large number of people in one country are infected with flu, can last several weeks.

What are the symptoms of flu?

It is common to confuse flu with a bad cold. Flu and cold symptoms may include a runny/blocked nose, sore throat, and cough. Here are some symptoms which a person with flu will have. These are not common heavy cold symptoms:

• high temperature
• cold sweats, shivers
• headache
• aching joints, aching limbs
• fatigue, feeling utterly exhausted
• gastro-intestinal symptoms, such as nausea, vomiting, and diarrhea, are much more common among children than adults

These symptoms may linger for about a week. The feeling of tiredness and gloom can continue for several weeks.

How serious is flu?

In the majority of cases flu is not serious - it is just unpleasant. For some people, however, there can be severe complications. This is more likely if you are elderly or have some other longstanding illness that can undermine your immune system. Your risk of experiencing severe flu complications is higher if:

• you are over 65
• you are a baby or a very young child
• you are pregnant
• you have some kind of heart or cardiovascular disease
• you have a chest problem, such as asthma or bronchitis
• you have a kidney disease
• you suffer from diabetes
• you are taking steroids
• you are undergoing treatment for cancer
• you have any longstanding disease that can significantly lower your immune system

Some of the complications caused by influenza may include bacterial pneumonia, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. Children may get sinus problems and ear infections.

What should I do if I have flu?

As flu is caused by a virus, antibiotics won't do any good, unless the flu has led to another illness. Some of the symptoms, such as headache and body pains may be alleviated if you take a painkiller. Some painkillers, such as aspirin, should not be given to children under 12 (Department of Health, United Kingdom). If you have flu you should:

• stay at home
• try to avoid contact with other people
• keep warm and rest
• make sure you consume plenty of liquids
• don't consume alcohol
• if you are a smoker stop smoking or cut your consumption down as much as you can
• try to get some food down (eat what you can)
• if you live alone, tell a relative, friend or neighbor that you have flu. Make sure someone can check in on you and do your shopping

If I have flu should I tell my doctor?

According The Department of Health, UK, you should only contact your doctor if you are frail or elderly, your temperature remains high after four to five days, your symptoms worsen, you think you are seriously ill, you become short of breath, and/or you develop chest pain. A phone call to your doctor if you are worried may be a better solution than making an appointment.

Flu in the USA

In the United States approximately 5% to 20% of the population gets flu, according to the Centers of Disease Control and Prevention (CDC). Over 200,000 people are hospitalized from flu complications each year, and about 36,000 people are estimated to die as a result of flu.

Flu in the world

According to the World Health Organization (WHO), in annual influenza epidemics 5% to 15% of the world's population become ill with upper respiratory tract infections. Hospitalization and deaths mainly occur in high-risk groups. It is estimated that between one quarter to one half of a million people die each year as a result of flu. In industrialized countries the majority of deaths as a result of flu occur among people over the age of 65 years.

How to prevent flu

Health experts and government agencies throughout the world say that the single best way to protect yourself from catching flu is to get vaccination every year. There are two types of vaccinations, the flu shot and the nasal-spray flu vaccine. The flu shot is administered with a needle, usually in the arm - it is approved for people older than six months, including healthy people and those with chronic medical conditions. The nasal-spray flu vaccine is a vaccine made with live, weakened flu viruses that do not make you ill.

A flu vaccine will contain three influenza viruses - One A (H3N2) virus, one A (H1N2) virus, and one B virus. As viruses adapt and change, so do those contained within the vaccines - what is included in them is based on international surveillance and scientists' calculations about which virus types and strains will circulate in a given year. You are protected about two weeks after receiving the vaccination.

Annual flu vaccinations should start in September or as soon as the vaccine is on hand and continue throughout the flu season, into January, and beyond. This is because the timing and duration of influenza seasons are never the same. Flu outbreaks usually peak at around January, but they can happen as early as October.

The flu vaccine is not suitable for some people

You should check with your doctor before deciding to have the flu vaccine if:

• you have a severe allergy to chicken eggs
• you have had a severe reaction to a flu vaccination
• you developed Guillain-Barré Syndrome within six weeks of receiving a flu vaccine
• you are less than six months old
• you have a fever with a moderate-to-severe illness. You should wait till you recover before being vaccinated

There are three types of flu viruses

Three types of flu viruses exist - infuenza A, influenza B and influenza C. Types A and B viruses cause seasonal epidemics which hit the USA and Europe virtually every winter. The type C influenza virus causes mild respiratory illness and is not responsible for epidemics.

Two proteins on the surface of influenza A viruses divide it into subtypes - the hemagglutinin (H) and the neuraminidase (N). 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes are known to exist. The current subtypes of influenza A viruses found in people are A (H1N1) and A (H3N2).

There are no B virus subtypes, but there are different influenza B virus strains.

Sources - Department of Health (UK), CDC, NIH, WHO.

Written by Christian Nordqvist
Original article date: 18th October 2004
Article updated: 3rd March 2009

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