What is the flu and what is a flu-like infection?
As reliably as every summer comes to an end, the flu season begins in the cold season. This infectious disease can affect the airways from the nose down to the bronchi. Influenza often affects larger population groups in the form of a flu epidemic. In Switzerland, for example, it usually drives between 100,000 and almost 300,000 people into medical treatment rooms every year. Several thousand of them have to be treated in hospital. And several hundred do not survive their flu infection. The risk of the disease leading to serious complications is particularly high in older people and the chronically ill.
But not everyone who moans “I’ve got the flu” with a cough and a sniffly nose has actually contracted influenza viruses. It is often a cold, which is also transmitted by viruses and can be quite stressful. However, they are different viruses from influenza and do not produce symptoms that can be as severe as those of influenza. While a cold usually only affects the respiratory tract, a “real” flu usually makes the whole body feel ill.
A cold (a flu-like infection) cannot develop into the flu. Conversely, a flu vaccination can only protect against influenza, but not against a flu-like infection.
Causes: How does the flu develop?
If you have the flu, you have probably inhaled infectious influenza viruses from another person. In addition to such a “droplet infection”, a “smear infection” or a “contact infection” can also be considered as a transmission route. In the case of a smear infection, you first touch an object that has flu pathogens on it, which you then transfer to your mouth or nose. In the case of a contact infection, you become infected by touching a sick person directly.
As soon as the flu viruses have entered the body, they begin their work: they attach themselves to the cells of the mucous membrane in the mouth and throat, penetrate them and multiply there. In order to defend itself, the organism reacts with inflammation – this inflammatory reaction produces the typical flu symptoms.
There are different influenza viruses; virologists divide them into two groups: Influenza A, with several subgroups, and Influenza B. Influenza A viruses cause bird flu and swine flu, among others.
Symptoms: How does the flu manifest itself?
The first signs of the flu usually appear suddenly and are clearly noticeable. Typical flu symptoms are:
- dry irritating cough
- Sore throat
- Fever (38.5 degrees or higher)
- Chills
- Headache
- Muscle and limb pain
In some cases, flu is accompanied by other symptoms. For example, vomiting, physical weakness, lack of appetite and dizziness.
However, it is also possible that the typical and less typical flu symptoms only occur in a mild form or are even absent. In such cases, it can be difficult to distinguish between influenza and a cold. Only a precise diagnosis can provide clarity.
Diagnosis: How can influenza be diagnosed?
If the clinical picture is unclear, your doctor can use a laboratory test to find out whether you have been infected with flu viruses. In order to obtain the necessary cell samples, a swab is usually taken from the nose or throat. A well-known analysis method for detecting influenza pathogens is the PCR test – you may remember it from the time when the PCR rapid test was mainly used to detect coronaviruses.
Another test method has a long English name, which is abbreviated to ELISA. The letter E stands for “enzymes”. These endogenous molecules can be used to detect whether the immune system has started to fight them. However, this is not a direct proof of the virus.
Prognosis: How does the flu progress?
After infection, it usually takes one to three days before the flu becomes noticeable. In some cases, the incubation period lasts four days.
If you are ill with influenza, it is highly likely that you will have recovered within a week. However, you should be aware that your flu can drag on for two weeks or even longer. Whether it heals with or without medication hardly changes the duration of the disease.
If you are infected with flu viruses, you can infect other people even if you do not (or not yet) feel ill. And once the last symptoms of the disease have subsided, there is still a risk of infection for about a week.
Flu becomes particularly dangerous when it opens the door to other illnesses. Unlike the common cold (a flu-like infection), influenza can lead to serious complications:
These diseases are either caused by the influenza viruses, or they are caused by bacteria as a result of influenza. In this case, we speak of a secondary bacterial infection (the first, primary infection was caused by the influenza viruses). The reasons why bacteria now also play a role are as follows: The viruses have damaged the mucous membranes of the respiratory tract to such an extent that bacteria have easy access here. In addition, the immune system is so busy or weakened by the virus defense that the body’s defenses against bacteria are often only effective to a limited extent.
In older people or flu sufferers with a weakened immune system, there is a risk of influenza becoming fatal. This is particularly the case if bronchitis or pneumonia develops as a secondary infection.
Treatment: How is influenza treated?
If you have been infected with flu viruses, your body does not accept the attack of the pathogens without doing anything: Your immune system defends itself by forming defense cells in the blood that produce antibodies. Their task is to target and destroy the intruders. Medical treatment is usually aimed more at alleviating the symptoms of the flu and preventing complications – for example with the help of antipyretic or anti-inflammatory medication.
However, your doctor may also give you a medication that specifically targets the activity and multiplication of the flu viruses. These antiviral drugs are called neuraminidase inhibitors. If possible, these flu remedies should be taken within 48 hours of the first flu symptoms appearing. The active ingredients can have side effects such as diarrhea, headaches and nausea. And they shorten the duration of the flu by one or two days at most.
Prevention: How do you prevent the flu?
If you want to avoid becoming infected with flu viruses, there are various measures you can take to protect yourself. You probably remember some of these measures from the time of the coronavirus pandemic: frequent and thorough hand washing, disinfecting surfaces, keeping your distance from potentially infectious people – and perhaps even a protective mask. Vaccination can also provide particularly effective protection. It should be given in good time – around October or November – because it takes around two weeks for the flu vaccination to take effect after the injection has been given. But you can also get vaccinated at the beginning of the year – some flu epidemics only spread in January and February.
Anyone who is otherwise healthy usually survives seasonal flu without any major problems. However, if you belong to a risk group, you should definitely follow the recommendations for prevention – otherwise influenza could lead to serious consequences. Risk groups are: Pregnant women, older people (over 65), patients with chronic diseases (e.g. cardiovascular diseases, diabetes, lung diseases) and people with a weakened immune system.
No one can know whether they themselves may be contagious and spread flu viruses – you can feel perfectly healthy and still have influenza pathogens in your body. A simple rule can therefore help to contain the spread of viruses (of all kinds): If you have to cough or sneeze, don’t put your hand over your mouth, but use the crook of your elbow.
Details of the treatments
