The pandemic of the disease caused by the coronavirus 2019, covid-19, and caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a global health crisis. In total, more than 564 million cases have been detected. 6.4 million have died and recovered, according to data from the World Health Organization (WHO), or about 536 million. In Spain, the figures speak of 13 million cases and almost 110,000 deaths.
Despite the development of vaccines and antivirals approved by the respective agencies, SARS-CoV-2 continues to spread around the world, with the frequent appearance of new viral variants.
The WHO said a week ago that a rise in covid-19 cases was expected in Europe this summer and urged governments to monitor the spread, with cases having tripled in the past month.
The European Center for Disease Prevention and Detection (ECDC) recognizes four variants of interest, i.e. those that indicate a significant impact on transmissibility, severity and/or immunity likely to have a impact on the epidemiological situation in the region.
“As countries in the European region lift the social measures that were previously in place, the virus will be transmitted at high levels during the summer,” said WHO Regional Director for Europe, Belgian Hans Kluge – . “This virus will not go away just because countries stop looking for it. It’s still spreading, it’s still changing and it’s still taking lives.”
With the BA.5 subvariant of Omicron, one of four declared to be of concern by the WHO, milder but more contagious, spreading across the continent, the 53 countries of the WHO European region are currently registering just under 500,000 daily cases, according to data from the organization. This represents approximately 150,000 daily cases at the end of May.
And to that we must add a problem: the flu (or influenza). The WHO estimates that around 1 billion people worldwide are infected with seasonal flu each year.
Of these, between 0.3 and 0.5% have a severe case of influenza. In total, there are between 290,000 and 650,000 annual deaths from influenza. So what if we are infected with influenza and SARS-CoV-2 at the same time?
The reality is that the two viruses are similar in several ways. They are airborne and highly contagious pathogens. Both flu and covid, but from what we know so far, the virus responsible for the latter spreads more easily. At the same time, covid can cause more severe illness than the flu in some people, and those who have tested positive may take longer to develop symptoms and remain contagious for longer periods of time. Despite this, it is not possible to differentiate the two viruses simply by paying attention to the symptoms because some of them are identical: fever, cough, fatigue, sore throat… They also belong to different virus families. : SARS-CoV-2 has the family Coronaviridae, while influenza belongs to the family Orthomyxoviridae.
To date, several clinical studies have reported co-infection of SARS-CoV-2 with other viruses, including human immunodeficiency virus (HIV), hepatitis B and C viruses, and influenza. These latter cases, in particular, were frequent at the start of the pandemic, before the application of masks and social distancing. A meta-analysis of studies published on the first 4 months of the pandemic showed viral co-infection with SARS and influenza in 3% of hospitalized covid patients.
Now, a New York University team, led by Benjamin Tenoever, has studied the interaction between SARS-CoV-2 and the influenza virus both in cells and in animal models, using the occurrence in mice. The animals received the 2 viruses simultaneously and were examined on days 1, 3, 5, 7 and 14 after infection. At the same time, two other groups of mice were inoculated with the viruses in different ways: one was infected first with the SARS-CoV-2 virus and three days later with influenza, and the other group in reverse order. Both groups were checked 1, 3 and 5 days after the second infection. Test results showed that the concurrent infection and the one in which SARS-CoV-2 went first, produced no changes. However, Tenoever’s team found that the flu virus interferes with the ability of SARS-CoV-2 to replicate in the lungs, even more than a week after the flu virus is no longer in the lungs. the body.
The data suggest that there are certain factors (intrinsic or induced by the influenza virus) that could limit the growth of SARS-CoV-2, but it is not yet clear whether this effect plays a role in the severity. of the disease.
“The research is important because the human population now has 2 circulating respiratory RNA viruses with high pandemic potential: SARS-CoV-2 and influenza,” note the authors in the study published in the “Journal of Virology”. Since both viruses infect the respiratory tract and can cause significant morbidity and mortality, it is imperative that we also understand the consequences of co-infection. Still, the results suggest that co-infection with SARS-CoV-2 and influenza A virus does not pose an imminent threat to humanity. This study could be used as an example of how an immune response to something unrelated can provide protection against SARS-CoV-2. »
The new studies aim to delve, as Benjamin Tenoever’s team progresses, into analyzes in humans that reflect the variety of age, gender, and also consider different diseases that negatively influence SARS- CoV-2. For our good.