Influenza, or flu, is a respiratory illness caused by a virus. Flu is highly contagious and is normally spread by the coughs and sneezes of an infected person. Although unpleasant, flu is rarely life-threatening.
You can also catch flu by touching an infected person, for instance, 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.
In this article, we explain the symptoms of flu, how it is treated, how it differs from a cold, and the best ways to prevent flu occurring.
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.
Woman with flu
Flu can be uncomfortable, but it is rarely life-threatening.
Confusing flu with a bad cold is common. Flu and cold symptoms may both include a runny/blocked nose, sore throat, and cough.
To help you tell them apart, below are some symptoms of flu that are different from a heavy cold:
cold sweats and shivers
aching joints and limbs
fatigue, feeling exhausted
There may also be gastrointestinal symptoms, such as nausea, vomiting, and diarrhea; these are much more common among children than adults.
Normally, symptoms linger for about 1 week. However, the feeling of tiredness and gloom can continue for several weeks.
It is worth noting that not every person with flu will have all of the symptoms; for instance, it is possible to have flu without fever.
Early symptoms of flu
Often, fatigue is one of the earliest signs of flu and cold. With flu, the fatigue is often more extreme. Other early symptoms can include cough, sore throat, fever, body ache, chills, and gastrointestinal changes.
As flu is caused by a virus, antibiotics cannot help, unless the flu has led to another illness caused by bacteria. Antivirals, such as oseltamivir (Tamiflu) and zanamivir (Relenza), may be prescribed in some circumstances.
Painkillers can alleviate some of the symptoms, such as headache and body pains.
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
eat if possible
It is a good idea for people that live alone to tell a relative, friend, or neighbor that they have flu and make sure someone can check in on them.
When to see a doctor
A doctor only needs to be informed if:
the individual is frail or elderly
their temperature remains high after 4-5 days
the individual feels seriously ill
they become short of breath and/or develop chest pain
If worried, a phone call to the doctor may be a better solution than making an appointment.
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:
adults over 65
babies or young children
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 develop sinus problems and ear infections.