Influenza

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.
A person 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 the influenza virus can spread before a person even knows they are infected.

Symptoms

Confusing flu with a bad common cold is common. Flu and common cold symptoms may both include a runny/blocked nose, sore throat, and cough.
below are some symptoms of flu that are different from a heavy common cold:

• high temperature
• cold sweats and shivers
• headache
• 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.

Treatment

As flu is caused by a virus, antibiotics cannot help, unless the flu has led to another illness caused by bacteria. Antivirals, may be prescribed in some circumstances.
Painkillers can alleviate some of the symptoms, such as headache and body pains. It is important to compare different products, and only take them under the advice of a medical professional.
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

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.

Risks

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
• 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 develop sinus problems and ear infections.

Prevention

In the United States, 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, globally, 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 - where a large number of people in one country are infected - can last several weeks. 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.

References:
https://www.medicalnewstoday.com/articles/15107.php