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.
According to the National Institutes of Health, between 5% and 20% of Americans get the flu each year. More than 200,000 people are hospitalized and 36,000 die annually because of flu in the United States.
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You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on flu
Here are some key points about influenza. More detail and supporting information is in the main article.
- Flu shares many symptoms with the common cold.
- Although the majority of flu cases are not serious, some people may experience severe complications.
- Antibiotics cannot be used to treat flu.
- People who have flu should try to avoid contact with other people to prevent spreading the virus.
- Approximately 5-20% of the US population will develop flu.
- Around the world, experts estimate that between one quarter to one half of a million people die each year as a result of flu.
- Experts agree that the best way to prevent flu is to get vaccinated each year.
- The flu vaccine is not suitable for certain groups of people, such as those who have a severe allergy to chicken eggs.
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 (note that these are not common heavy cold symptoms):
- high temperature
- cold sweats, shivers
- 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.
Seasonal patterns of influenza and upper airway infection were found to be linked to a higher incidence of narcolepsy, researchers from Stanford University School of Medicine reported in Annals of Neurology (August 2011 issue). Narcolepsy is a neurological disease characterized by excessive sleepiness and sleep attacks at inappropriate moments, such as during work.
Treatments for 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:
If you have flu, recommendations include staying at home, getting lots of rest and ensuring you drink plenty of liquids
- 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
Recent developments on flu from MNT news
When we are ill with a virus infection, it is because the virus has entered cells in our body and taken over their machinery to make copies of itself. Finding ways to disrupt this process is important for antiviral drug development. Now, a new study reveals how the flu virus relies on a protein in the host cell to help it complete its mission.
A new study may explain why flu appears to hit men harder than women. Researchers who tested various forms of the female sex hormone estrogen - which is also present in men - on nasal cells from men and women, found the compounds reduced virus replication in the female but not the male cells.
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.
On the next page, we look at how flu can be prevented and the different types of flu.