It is known that viral infections can “overlap” one another: different viruses can infect one person at the same time. This can often have a bad effect on the course and prognosis of the disease. In 2020, the seasonal surge in the incidence of SARS and influenza in the northern hemisphere promises to coincide with the second wave of COVID-19. Let’s figure out if there is a risk of complications with this combination of viruses.
Coronaviruses and concurrent infection
SARS outbreaks that cause seasonal coronaviruses often coincide with or precede influenza epidemics. Common coronaviruses during the cold season infect humans simultaneously with other respiratory viruses in 11-41% of cases. Scientists fear that such an overlap may be characteristic of the new SARS-CoV-2 coronavirus.
SARS и MERS
Scientists have investigated parallel infection (coinfection, mixed infection) with coronaviruses and other pathogens during previous outbreaks caused by the “close relatives” of SARS-CoV-2, the pathogen COVID-19. During an outbreak of Severe Acute Respiratory Syndrome (SARS) in Hong Kong, scientists discovered coinfection: coexisted with coronavirus metapneumovirus… In the outbreak of Middle East respiratory syndrome caused by the MERS-CoV coronavirus, there was described mixed infection with influenza A. But on both occasions, the researchers were unable to determine how this affects the severity of the disease.
SARS-CoV-2 and other viruses
Co-infection is possible
The new coronavirus SARS-CoV-2 can also coexist with other respiratory viruses in the human body, in the same cells. A study that was conducted in China, showed that influenza A virus coexisted with the new coronavirus in 10% of cases, influenza B virus – in 5%, respiratory syncytial virus – in 3%. Viruses were identified in 85 people who died from COVID-19.
Similar data received scientists from Iran: COVID-19 is often accompanied by infection with influenza viruses, parainfluenza, adenoviruses. In children, they found coinfection only with metapneumovirus. However, in both cases, the researchers did not give an answer as to whether the course of the disease became worse due to the “cohabitation” of viruses.
Coinfection can affect the severity of the disease
Small scientific work Chinese researchers showed that patients with COVID-19 and its “mix” with the flu died with approximately the same probability. But other studies have led scientists to conclude that coinfection can worsen the course of the disease. According to data obtained in Wuhan, those infected with the new coronavirus and influenza B virus simultaneously have the disease flowed heavier than average in COVID-19 patients and with COVID-19 coinfection with influenza A.
In September 2020 on the website for preprints medrxiv.org appeared a study by British scientists in which they described a sample of more than 19 thousand patients with flu-like symptoms. In 58 cases, patients were concurrently infected SARS–CoV-2 and flu. The authors concluded that with the flu, the risk of infection SARS–CoV-2 drops by 58%, which may indicate competition between viruses. But in patients with confection, the risk of death was 2.27 times higher than with normal COVID-19. Scientists have suggested that synergy (increased effect) between the two viruses is possible.
Little data, but prevention is needed
Thus, today’s scientific evidence suggests that co-infection is possible. It can lead to worse illness and an increased risk of death. A large number of gaps remain in science: the studies cited were mostly small, they did not take into account whether patients were vaccinated against influenza, in addition, some of their data are not consistent with each other.
Considering that simultaneous infection CODID-19 and influenza can lead to serious consequences, this year the prevention of influenza, primarily vaccination, is of particular importance. Brazilian scientists showedthat patients who have been vaccinated against the flu are less likely to develop severe symptoms COVID-19 requiring treatment in the intensive care unit. You can find out more about the need for a flu shot this year in our resource.