The winter season is in full swing and various respiratory viruses are going around. What happens if you get several such viruses at the same time, such as corona and flu?
There has been a flu epidemic in the Netherlands since mid-December. Flu is a respiratory infection, or an airway infection. Other viruses, such as the rhinovirus (the main cause of the common cold), the human metapneumovirus, the RS virus and the SARS-CoV-2 virus are also so-called respiratory viruses.
It is possible to become infected with several respiratory viruses at the same time. This is called a co-infection or double infection.
“It depends on which viruses are involved, but an infection with both the flu and the corona virus can certainly occur at the same time,” says Izabela Rodenhuis-Zybert. She is an experimental viro-immunologist at the Department of Medical Microbiology and Infection Prevention at the University Medical Center Groningen. Viral co-infections can also be associated with a bacterial or fungal infection.
Co-infections of respiratory viruses mainly occur in the autumn and winter months. This period is also called the respiratory season. These co-infections are most common in children up to five years old. “In this group, 10 to 30 percent of patients are confronted with a co-infection,” says Rodenhuis-Zybert.
Infection with more than two viruses is also possible
An infection with more than two viruses at the same time is also possible. In some cases, a person becomes infected with as many as three to four viruses at the same time. This happens especially in children. For example, they are exposed to many viruses at school and daycare.
We often see that one virus is dominant. This way we can indicate which virus is causing complaints at that time.
“Some of these viruses get them for the first time. As a result, children sometimes cannot clear a virus right away. Adults have often already built up some memory defenses,” says Corine Geurts van Kessel, medical microbiologist at the Viroscience department of Erasmus MC in Rotterdam. .
Nevertheless, especially in recent months, you see that several respiratory viruses are also emerging at the same time in adults, says Geurts van Kessel. “We often see that one virus is dominant. This way we can often indicate which virus is causing complaints at that moment. But sometimes this is difficult to determine. It is not always very black and white.”
Viruses can change quickly
In a co-infection of the same host cell, it is possible that different viruses will interact with each other. “Sometimes viruses are so similar that they can recombine with each other. In this way, viruses can change quickly,” says Geurts van Kessel. This can happen with different types of the influenza virus, but also between different types of viruses.
Rodenhuis-Zybert refers to one study where scientists looked at what happens if you infect a cell with influenza A (flu) and the RS virus at the same time. This experimental co-infection led to the creation of hitherto unknown hybrid particles.
These particles are contagious and can infect cells that influenza A itself cannot infect. How efficient this phenomenon is and whether it can also happen in a human is unknown.
Effects of co-infection are still unclear
It is still unclear what the effects of a co-infection could be for the infected person and on the course of the disease. Research results are sometimes contradictory. For example, a small study in mice and ferrets found that viral co-infections may contribute to the severity of the disease. Other small studies show that viral co-infections have no effect on the course of the disease.
A co-infection is not immediately alarming. It says more about the amount of viruses that are currently circulating.
“More research is needed to be able to say something about the clinical picture and course, the spread of the virus and the long-term effects on the immune system,” emphasizes Rodenhuis-Zybert.
Disease course does not have to change drastically
According to both experts, there is no reason to panic. Diagnostics are getting better and because more and more detailed attention is being paid to what happens during a virus infection, more and more is coming to light.
The course of the disease does not have to change drastically due to co-infection, especially if you are otherwise healthy. However, it can cause a longer recovery time in people with a reduced immune system.
“Co-infection occurs. It is not immediately alarming. It says more about the amount of viruses that are currently circulating,” says Geurts van Kessel. “It is not expected, for example, that influenza suddenly coincides with the corona virus and that you then get a kind of influenza corona. That chance is very small.”
