Influenza, or flu, is a respiratory illness caused by a virus. Flu is highly contagious and is usually spread by the coughs and sneezes of an infected person.
You can also catch flu by touching an infected person (e.g. shaking hands). Adults are contagious 1-2 days 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.
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.
It is estimated that 250,000-500,000 people die each year as a result of flu. In industrialized countries, the majority of deaths occur among people over the age of 65.
A flu epidemic, when a large number of people in one country are infected with flu, can last several weeks.
Contents of this article:
Fast facts on flu
Here are some key points about flu. More detail and supporting information is in the main article.
- Antibiotics cannot be used to treat flu
- Approximately 5-20 percent of Americans will develop 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.
Below are some flu symptoms that are different from heavy cold symptoms:
- High temperature
- Cold sweats, shivers
- Aching joints and limbs
- Fatigue, feeling exhausted
- Gastro-intestinal symptoms, such as nausea, vomiting, and diarrhea (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 in very young children, in the elderly, and for individuals with other longstanding illness that can undermine their immune system.
The risk of experiencing severe flu complications is higher for certain people:
- Over 65s
- Babies or young children
- Pregnant women
- Individuals with heart or cardiovascular disease
- Those with chest problems, such as asthma or bronchitis
- Individuals with kidney disease
- People with diabetes
- People taking steroids
- Individuals undergoing treatment for cancer
- Those with longstanding diseases that reduce immune system function
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, by researchers from Stanford University School of Medicine. Narcolepsy is a neurological disease characterized by excessive sleepiness and sleep attacks at inappropriate moments, such as during work.
Treatments for flu
Recommendations include staying at home, getting lots of rest, and drinking plenty of liquids
As flu is caused by a virus, antibiotics cannot help, unless the flu has led to another illness caused by bacteria. Some of the symptoms, such as headache and body pains may be alleviated by painkillers.
Some painkillers, such as aspirin, should not be given to children under 12.
Individuals with flu should:
- Stay at home
- Avoid contact with other people where possible
- Keep warm and rest
- Consume plenty of liquids
- Avoid alcohol
- Stop smoking
- Eat if possible
- People that live alone should tell a relative, friend, or neighbor that they have flu and make sure someone can check in on them
Should people with flu tell their doctor?
A doctor should only be informed if the individual is frail or elderly, if their temperature remains high after 4-5 days, if symptoms worsen, or if the individual feels seriously ill, becomes short of breath, and/or develops chest pain.
If worried, a phone call to the doctor may be a better solution than making an appointment.
Health experts and government agencies throughout the world say that the single best way to protect oneself from catching flu is to get vaccinated 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 anyone older than 6 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 cause illness.
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. Protection begins about 2 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.
An infant whose mother was given a flu jab while pregnant is 50 percent less likely to be hospitalized for flu than other infants whose mothers were not given the shot while pregnant, according to researchers from Wake Forest Baptist Medical Center.
The flu vaccine is not suitable for some people
Certain individuals should check with their doctor before deciding to have the flu vaccine:
- Individuals with a severe allergy to chicken eggs
- Individuals who have had a severe reaction to a flu vaccination in the past
- Individuals who developed Guillain-Barré Syndrome within 6 weeks of receiving a flu vaccine
- Children under 6 months old
- Individuals experiencing a fever with a moderate-to-severe illness should wait until they recover before being vaccinated
Types of flu viruses
Three types of flu viruses exist - influenza A, influenza B, and influenza C. Types A and B viruses cause seasonal epidemics which hit the U.S. and Europe virtually every winter. The type C influenza virus causes mild respiratory illness and is not responsible for epidemics.