Introduction

photo of woman blowing her nose (PantherMedia / subbotina) People often talk about having the flu (influenza) when they come down with a cold. Yet the two illnesses progress in very different ways and also typically have different signs and symptoms.

Colds are much more common than the flu. They also start quite slowly, while the viruses that cause the flu strike quickly and cause more severe symptoms, even in people who are otherwise quite healthy. The flu makes you feel very ill very quickly. A cold does not usually cause any serious harm, and is over within a week with or without treatment. It is a good idea to see a doctor if you have the flu, and it may take some time before you fully recover.

Cold and flu treatments mainly aim to relieve symptoms. The only medicines available that fight directly against the flu viruses can at most reduce the time someone is ill. But a number of things can be done to avoid infection in the first place.

Symptoms

Many symptoms of “real” flu – also called influenza - are similar to those of a common cold. They might include fever, headache, joint pain, and a stuffy or runny nose. But flu usually affects the entire body, and not just the airways. It typically starts quite suddenly with very intense symptoms. These usually improve a lot within one week. You might have a cough or feel exhausted for longer, though.

Flu symptoms include:

  • Fever: When your body temperature rises to between 38 and 40 degrees Celsius (100 to 104 Fahrenheit), or even higher
  • Muscle and joint pain throughout the entire body (myalgia and arthralgia)
  • Headache
  • Severe fatigue and general feeling of being very ill
  • Dry cough
  • Stuffy and/or runny nose
  • Loss of appetite
  • Extreme tiredness

Babies or young children may also have stomach and bowel trouble like nausea or vomiting.

If you think you might have the flu, it is a good idea to go to the doctor. This is especially important if someone already has diseases that increase the risk of developing complications – such as a chronic lung disease or diabetes. Contact with people at a higher risk also makes it more important to see a doctor.

Causes

Flu is caused by viruses. Viruses are microscopically small – even smaller than bacteria. They multiply very quickly after they have entered the body. The body’s immune system needs some time to learn how to produce antibodies to fight the viral infection.

There are hundreds of flu viruses, belonging to different groups. The influenza A and influenza B viruses are the most dangerous for humans. If you are infected with a particular virus, you will also develop immunity against that virus.

Effects

Sinusitis (an inflammation of the sinus cavities) is one very common complication of the flu. Here the cavities surrounding the nose fill with an infectious fluid. Common sinusitis symptoms include headaches and a stuffy nose.

In babies and young children, respiratory infections often lead to a middle ear infection (acute otitis media).

In rare cases, a flu can become more serious and lead to complications like pneumonia. The chances of this happening are especially high in people with a weakened immune system, including babies and toddlers, people with lung diseases or immune system problems, and people over the age of 65.

Prevention

Flu and cold viruses are spread by droplet infection: when someone who is infected coughs or sneezes, droplets containing the viruses are released into the air. Viruses can also spread when you blow your nose, ending up on the used tissue and your hands. These viruses can then pass to other people or objects. They can also be easily transmitted from person to person wherever a lot of people touch the same object, like doorknobs or handrails in a subway car or bus. And cold and flu viruses are more likely to spread if people shake hands or hug each other.

The most effective thing you can do to protect yourself and others from these viruses is stop them spreading. For example, by washing your hands frequently and throwing away used tissues.

Even after the symptoms have gone away, you may remain contagious for up to one week. So it is a good idea to avoid contact with others during this period and to work from home if possible.

A flu vaccination can also help protect you from flu viruses.

Research summaries

Treatment

Many people turn to home remedies like chicken broth or herbal teas to relieve flu symptoms. Getting plenty to drink is also considered to be important. But there is no scientific proof that any of these things helps speed up recovery. So there is no good reason to use any of these remedies or drink more fluids if it does not feel right.

A number of freely available products like vitamin supplements or inhalation devices are marketed for the treatment of colds, flus and coughs. But there is no compelling evidence that they are effective against the flu. Painkillers such as acetaminophen (paracetamol), acetylsalicylic acid (ASA, the drug in medicines like Aspirin) and ibuprofen can relieve pain and lower fever. But children and teenagers should not take ASA because in rare cases this drug can cause a serious brain condition in these age groups.

In addition to these over-the-counter products, special flu medication is also available. The most common of these in Germany is oseltamivir (trade name: Tamiflu). Oseltamivir is prescription-only and needs to be taken within two days after the flu starts. If symptoms have already persisted for a longer time, this medication will not have any effect on the course of the flu. Some research suggests that oseltamivir could reduce the period of illness by up to one day. But it often causes nausea and vomiting.

It is not clear whether it helps to prevent complications. Some people think that antibiotics will help in the treatment of flu. But antibiotics can only fight bacteria, not viruses. So antibiotics only help if you have a bacterial infection of the airways as well as a viral infection. Unless there are signs of bacterial infection, there is no point in taking antibiotics.

Research summaries

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