The flu would multiply by 2.5 on average the rate of transmission of Covid-19 during the period of common circulation of the two viruses.
- Previous studies have shown that influenza will lead to higher production of the receptors that are used by the coronavirus to attach to human respiratory cells.
- To decrease the effects of influenza on coronavirus transmission, the study authors advocate for influenza vaccination as additional protection against Covid-19.
The upcoming arrival of winter and the flu has scientists wondering as the coronavirus pandemic continues to hit populations. In an attempt to predict the consequences of this collusion of the two viruses, scientists from the Max Planck Institute for Infection Biology in Berlin and the Institut Pasteur in Paris used a mathematical model to study the first months of the coronavirus pandemic in Europe. It has shown that the decrease in Covid-19 cases in the spring is not only linked to the measures taken to contain it but also to the end of the flu season.
The flu would facilitate infection with Covid-19
Previous studies have shown that influenza will lead to higher production of the receptors that are used by the coronavirus to attach to human respiratory cells. Based on this principle, the resumption of the flu season which will accompany the first days of cold should multiply by 2.5 the transmission of coronavirus, according to the researchers’ calculation tools.
To achieve this result, they developed a mathematical model of coronavirus transmission and mortality to understand the influence of the flu season on the pandemic. The spread of the coronavirus during the first half of 2020 in four European countries, Belgium, Norway, Italy and Spain was thus modelled. Several parameters were then integrated such as the time of infection, the duration of transmission or the measures taken to slow the spread, such as social distancing or confinement. The results of this study were the subject of a pre-publication on September 9 on medRxiv, which still needs to be reviewed by other researchers before being published in a peer-reviewed journal. “These estimates align with previous research”, told Matthieu Domenech de Cellès of the Max Planck Institute and lead author of the study, to Reuters.
Using mathematical modeling, the researchers tested different hypotheses about the effects of influenza on the pandemic. The results show that during a period of co-circulation of the two viruses, the flu can multiply the transmission rate of the coronavirus by 2 or even 2.5. Comparing their model with data on daily deaths in the four countries allowed them to demonstrate that their model is consistent with observed mortality.
Soon the twindemic
To decrease the effects of influenza on coronavirus transmission, the study authors advocate for influenza vaccination as additional protection against Covid-19. “In Italy, higher rates of flu vaccination have been associated with lower rates of death from Covid-19adds Matthieu Domenech de Cellès to Reuters. Additionally, a US study of nearly 11,700 people tested for Covid-19 found that those who had flu shots were less likely to test positive..”
Vaccination against influenza would relieve hospitals and contain the potential effect of influenza on the transmission of the coronavirus. “Before the next ‘twindemic’ (the simultaneous circulation of the coronavirus and the flu, editor’s note), our results suggest the need to increase vaccination against the flu”, says the researcher. In France, several voices are raised to make this vaccination compulsory. The Academy of Medicine wishes “make influenza vaccination compulsory for all caregivers and social workers in contact with vulnerable people, in particular in nursing homes, institutions, hospitals and nurseries”, according to his press release dated May 13.
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