Corona or flu? Why we are particularly susceptible to viruses now
Cough, sore throat, runny nose: With the low temperatures, colds and the flu are also on the rise. But why is that? And how can you tell if you have a cold, the flu or coronavirus? The most important questions and answers:
26.11.2025, 07:18
26.11.2025, 10:43
SDA
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- The symptoms of flu and a cold are similar. However, they are caused by different viruses.
- And how can you tell whether you have a cold, flu or coronavirus?
- Below you will find the most important questions and answers.
Is the flu epidemic about to start?
Yes, the start of the flu epidemic is imminent. In Switzerland, the number of visits to the doctor for flu-like illnesses rose sharply last week, according to figures from the Federal Office of Public Health (FOPH) on November 19, 2025.
Around 5500 people visited a doctor due to a sudden onset of high fever, cough or sore throat - almost 90 percent more than in the previous week. The number of laboratory-confirmed flu cases has also risen by around 30 percent. However, at 137 cases, it is still at a relatively low level, as the FOPH emphasizes in its assessment of the situation. According to the FOPH, wastewater monitoring also shows an increase in influenza viruses in several regions. "Overall, the epidemiological indicators suggest that the start of the flu epidemic is imminent", according to the FOPH's assessment
Difference between flu and a cold?
The symptoms of flu and a cold are similar. However, they are caused by different viruses. The flu is caused by influenza viruses. In contrast, colds or flu-like infections, as they are technically known, are triggered by a variety of viruses. The main trigger for colds is the rhinovirus.
The flu is more dangerous than a cold. Unlike other viral colds, it can lead to numerous complications, especially in chronically ill people, pregnant women and the elderly, as the Federal Office of Public Health (FOPH) explains on its website. In Switzerland, several hundred people die from the flu every year.
However, you do not become immune to the common cold. On average, young children catch between three and thirteen colds a year, depending on the source. Adults are also affected two to three times a year. However, the average adult does not catch the flu every year.
And what about corona?
Corona is the term used to describe an infection with the SARS-CoV-2 virus. According to the FOPH, the coronavirus load in wastewater has been decreasing again in most regions since peaking in September. Currently, it is mainly the XFG variant, nicknamed "Frankenstein", that is detected in wastewater. In a report published in June, the World Health Organization (WHO) assessed the health risks of this variant as low.
How do I recognize what I have?
Recognizing the differences is difficult. There are no clear symptoms where you can tell for sure whether it is one or the other. Typically, people with the real flu usually feel ill from one moment to the next. This usually includes a sudden high fever. With corona, on the other hand, there is often a loss of taste and smell. In contrast, cold symptoms increase slowly.
Another distinguishing feature is muscle and joint pain all over the body, which only affects patients with the flu. Headaches are also typical of flu patients. People with a cold, on the other hand, usually suffer from milder symptoms. Muscle pain rarely occurs with colds. While a cough tends to occur towards the end of the course of a cold, people with flu also struggle with a dry, irritating cough right at the beginning of the illness.
Why do waves of flu and colds occur in winter?
Both colds and flu are triggered by viral infections and not by the cold. Researchers from the "Common Cold Unit" at Harvard Hospital in Salisbury (UK) proved this back in the 1950s. In various experiments at the time, they deliberately infected volunteers with cold viruses. Some of the study participants were exposed to draughts or had to wear wet socks. It turned out that only those who were actually infected with the virus developed cold symptoms - but not those who were merely exposed to the cold.
The cold indirectly contributes to making us more susceptible to illness. Firstly, people spend more time indoors in winter, where pathogens can be transmitted more easily.
Secondly, cold air is dry. This makes the protective lipid layer of viruses harder, making them more robust. In addition, the winter air also dries out the mucous membranes in the nose and throat. Without a protective layer of mucus, viruses can infect the cells more easily.
