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A recent study by researchers from the Max Planck Institute for Infection Biology, the Pasteur Institute, and the International Center for Infection Research (CIRI) indicates that the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is impaired for the flu. . Virus infection during the initial period of the 2019 coronavirus epidemic (COVID-19) in Europe. The study is currently available at medRxiv * Server prepress.
Since its emergence in December 2019 in China, the highly prevalent SARS-CoV-2 virus has infected more than 27.99 million people worldwide and killed 906,122 people. Due to the lack of curative interventions or adequate vaccines, many preventative measures have been taken to address the epidemic, such as nationwide closures in more than 100 countries.
With regard to potential risk factors, several studies have shown that the elderly, men, and people with comorbidities (cardiovascular and / or lung disease, diabetes, kidney disease, and cancer) are more likely to develop a severe form of COVID- 19, which is associated with a higher mortality rate. .
Potential drivers of SARS-CoV-2 transmission in Belgium, Italy, Norway and Spain. A: A timeline for the Agility Index, which is a nationwide aggregate measure of the number and severity of non-pharmaceutical control measures implemented by governments. The dashed vertical line indicates the beginning of the national blockade. B: A schedule of influenza occurrence, calculated as the product of the occurrence of influenza-like illnesses and the breakdown of samples positive for any influenza virus. The vertical dashed lines define the period of interference between SARS-CoV-2 and influenza, which was defined as the period between the assumed start date of SARS-CoV-2 community transmission and 6 weeks after the peak. of the influenza pandemic. In each country, the time series presented as covariates, which modulate the SARS-CoV-2 transmission rate, were incorporated into the model. In B, the y-axis values differ for each plate.
The study hypothesis
With regard to seasonal viral infection in the human respiratory system, evidence indicates that the interaction between circulating pathogens during a pandemic or epidemic can be beneficial or unfavorable in terms of virus spread or disease severity. For example, infection caused by influenza virus has been shown to prevent secondary infection caused by respiratory syncytial virus in rodents. On the contrary, there is evidence to suggest that respiratory influenza infection may increase the expression of angiotensin-converting enzyme 2 (ACE2), a receptor in the respiratory epithelium that interacts with the SARS-CoV-2 protein and facilitates the entry of the virus. In human cells.
Given significant past experience on the impact of existing pathogens on spreading to the pandemic, the scientists in the current study hypothesized that the common influenza virus may have influenced the spread of SARS-CoV-2 in Europe during the initial phase of the Covid. -19 pandemic.
study design
Scientists have developed a population-based random model for the transmission of SARS-CoV-2 and COVID-19-related deaths. Assuming that death occurred in 1% of all infections, the scientists combined a representative distribution of virus generation time, the duration between onset of symptoms, and death in their model. It also incorporated the stringency index, which is a measure of the number of control measures (lockdowns, workplace / school closures, travel restrictions, etc.) that governments have taken during the pandemic and their stringency. They evaluated the effect of the severity index on the spread of the virus. The effect of influenza infection on the prevalence of SARS-CoV-2 was evaluated by incorporating a time series analysis of the incidence of influenza in the model. Information on influenza cases in four European countries, including Belgium, Italy, Norway, and Spain, was obtained from the World Health Organization.
![Potential drivers of SARS-CoV-2 transmission in Belgium, Italy, Norway and Spain. A: A timeline for the Agility Index, which is a nationwide aggregate measure of the number and severity of non-pharmaceutical control measures implemented by governments. The dashed vertical line indicates the start of the national blockade [16]. B: Chronology of influenza incidence, calculated as the product of the incidence of influenza-like illness and the breakdown of samples positive for any influenza virus (see also Figure S1 for a chronology of the last two variables). The vertical dotted lines define the period of interference between SARS-CoV-2 and influenza, defined as the period between the suspected start date of community transmission of SARS-CoV-2 and 6 weeks after the peak of a pandemic of influenza. [46]. In each country, the time series presented were incorporated as covariates, which modulated the SARS-CoV-2 transmission rate in our model (see Methods). In B, the y-axis values differ for each plate.](https://news.google.com/image.axd?picture=2020%2f9%2f%402020.09.07.20189779v1.jpg "Potential drivers of SARS-CoV-2 transmission in Belgium, Italy, Norway and Spain. A: A timeline for the Agility Index, which is a nationwide aggregate measure of the number and severity of non-pharmaceutical control measures implemented by governments. The dashed vertical line indicates the start of the national blockade [16]. B: Chronology of influenza incidence, calculated as the product of the incidence of influenza-like illness and the breakdown of samples positive for any influenza virus (see also Figure S1 for a chronology of the two last variables). The vertical dashed lines define the period of interference between SARS-CoV-2 and influenza, defined as the period between the assumed start date of community transmission of SARS-CoV-2 and 6 weeks after the peak of a pandemic of influenza. [46]. In each country, the time series presented were incorporated as covariates, which modulated the SARS-CoV-2 transmission rate in our model (see Methods). In B, the y-axis values differ for each plate.")
Data on presumptive influenza (A) and influenza virus (B) syndromic data for Belgium, Italy, Norway and Spain. In A, the red bars represent the number of samples positive for any influenza virus and the gray bars that are negative.
Important notes
Scientists have consistently observed that there is a 2- to 2.5-fold increase in transmission of SARS-CoV-2 during the period that the influenza virus and SARS-CoV-2 have been present together. Regarding control measures, they found that the strict implementation of control measures was associated with less transmission of the virus.
Based on descriptive statistical analysis of the model data, the scientists believe that their model effectively predicted the morbidity and mortality associated with SARS-CoV-2 during the study period.
Predictions given by the study model
Based on the data from the model, the scientists predicted that people who had recently had an influenza infection were more likely to develop SARS infection. This prediction was justified by observations from previous studies that showed increased transmissibility or susceptibility in people infected with the influenza virus and SARS-CoV-2.
Studies investigating the frequency of co-diagnosis of influenza polymerase chain reaction (PCR) and SARS-CoV-2 infection showed significantly variable results according to the prediction made in the current study. These discrepancies in study results may be due to differences in incubation times for influenza virus (~ 1 day) and SARS-CoV-2 (approximately 5.7 days). By the time SARS-CoV-2 reaches the level of detection in the body, the influenza virus may not be present due to the short incubation period.
Another prediction they made is that people who received the flu vaccine were less likely to have SARS-CoV-2 infection. This prediction is in line with the results of the previous study showing that influenza vaccination is associated with lower rates of SARS-CoV-2 infection and deaths associated with COVID-19.
Although the effect of influenza infection on the transmission of SARS-CoV-2 is clearly evident, the current study was conducted without controlling for a major confounder, age, which is known to affect influenza infection and SARS- CoV-2.
According to the scientists, this could be a potential limitation of the study. Scientists also believe that, in addition to the influenza virus, the effect of other respiratory viruses should also be tested for more comprehensive monitoring.
With regard to control measures, the scientists believe that the effect they observed may be specific to Europe, where the number and intensity of control measures increased gradually during the epidemic.
*Important note
medRxiv It publishes preliminary scientific reports that have not been peer-reviewed and therefore should not be considered conclusive, directing clinical practice / health-related behavior, nor treated as static information.
