There is a lack of information about the difference between influenza—‘real’ flu—and the common cold. Most people struggle to distinguish between these two diseases, and this often leads to irritation and the perpetuation of myths.

This was the key finding from a recent international study conducted in Austria, Belgium, and Croatia under the supervision of Kathryn Hoffmann, MD, MPH, an associate professor and lecturer in the division of general and family medicine at the Medical University of Vienna. Similar misconceptions were found in all three countries.

“Influenza and the common cold are completely different things,” says Hoffmann. “The clearly delineated influenza viruses cause a potentially serious illness. The common cold, on the other hand, is caused by hundreds of different infectious viruses. In the vast majority of cases, the progression and symptoms of the illness are much more benign. Contrary to popular belief, the common cold can never turn into real flu.”

It is easy to distinguish between the two diseases, particularly in the early stages. Influenza comes on suddenly with limb pain and fever in people who, a few hours earlier, felt absolutely fine. By contrast, a common cold usually starts with a sore throat, a blocked nose, and a cough, and comes on more gradually. Body temperature rises much more gradually.

“Our study shows that, if fever is one of the symptoms, people immediately think of ‘real’ flu,” says Hoffmann.

This is also the reason why many people who have been vaccinated against flu and still develop fever and flu-like symptoms, believe that the vaccine doesn’t work.

“They become skeptical of vaccinations, even though they are only suffering from a common cold—which, unfortunately, you can still get, even though you have had the flu jab,” Hoffmann explains.

It is therefore always advisable to be vaccinated against seasonal influenza, which, in serious cases, can prove lethal. A study carried out for the Vienna region in 2013, under the supervision of Theresia Popow-Kraupp, MD, a professor of virology at the Medical University of Vienna, revealed that, in Vienna alone, around 300 people die during a seasonal flu outbreak as a consequence of the illness, which can often last 2 or 3 weeks.

However, even though one can protect oneself from influenza by having the vaccination (the relevant seasonal vaccine is between 60% and 95% reliable), one has no protection against infectious common cold viruses.

“At some point the viral threshold that our immune system can withstand is exceeded, and then we develop a cold,” Hoffmann explains. “However, we can raise this threshold by healthy lifestyle habits that strengthen the immune system or by scrupulous hand hygiene.”

Even the term ‘cold’ is not really accurate. It is not yet clear whether one is more likely to succumb to a virus, if one gets cold. Whatever the case, the critical factor is contact with the viral pathogens.

In contrast to ‘real’ flu, however, people usually recover from a common cold in about 5 days, so long as they rest and look after themselves.


  1. Mayrhuber EA, Peersman W, van de Kraats N, et al. “With fever it’s the real flu I would say”: laypersons’ perception of common cold and influenza and their differences; a qualitative study in Austria, Belgium, and Croatia. BMC Infect Dis. 2018;18(1):647; doi: 10.1186/s12879-018-3568-9.

Featured image: Microphotograph of the H1N1 influenza virus. Photo courtesy US Centers for Disease Control and Prevention.