The latest research has been focused on the fundamental role of 'superspreaders' in the spread of the virus.
Several studies have pointed to the enormous incidence of this type of infected person in the spread of the virus, who, due to their greater contagiousness, are capable of infecting a large number of people.
In fact, a study by the Center for the Mathematical Modelling of Infectious Diseases in the United Kingdom has concluded that around 80% of the secondary infections of coronavirus are produced by a tiny fraction of those infected: the 'superspreaders', who account for only 10% of the total.
Moreover, a study carried out by the University of Santiago de Compostela has warned that this type of infected people could be the main drivers of the pandemic, even more than the new strains of coronavirus that have proven to be more contagious.
For this reason, research focused on this type of coronavirus patient profile has been intensified. The goal is to learn more about the disease in order to facilitate diagnosis and find effective measures to curb its rapid spread.
A recent study by researchers at Tulane University, Harvard University, MIT and Massachusetts General Hospital (USA) has established the three factors that trigger the likelihood of becoming a superspreader:
These three factors correlate with the propensity to exhale more respiratory droplets, which are the main spreaders of SARS-CoV-2, the virus that causes COVID-19, and trigger the possibility of turning the individual into a superspreader, capable of causing at least eight infections of the disease.
After analyzing data from an observational study of 194 healthy individuals and an experimental study of non-human primates with coronavirus, the researchers found that the amount of aerosol particles exhaled varied greatly among subjects.
Older people, with higher body mass indexes (BMI) and with an increasing degree of COVID-19 infection, had three times the number of exhaled respiratory droplets than the other study groups.
In the study with humans, the researchers found that 18% of the subjects accounted for 80% of the exhaled particles in the group, reflecting a distribution of exhaled aerosol particles that follows the 20/80 rule observed in other infectious epidemics.
This rule confirms the theory held in other studies noted above: 20% of coronavirus-infected individuals are responsible for 80% of transmissions.
For their part, the study on non-human primates was useful to establish a correlation between the increase in aerosols expelled and the degree of infection.
The researchers observed that as the infection progressed, the viral particles became smaller and thus more likely to be easily expelled when coughing, talking or breathing. At the height of infection, these droplets can reach the size of a single micron.
Although the study published in the journal 'Proceedings of the National Academy of Sciences' (PNAS) has highlighted the pivotal role of superspreaders in the pandemic, the researchers wanted to warn that anyone is prone to spread the virus.
"While our results show that the young and healthy tend to generate far fewer droplets than the older and less healthy, they also show that any of us, when infected with COVID-19, can be at risk of producing a large number of respiratory droplets," concludes David Edwards, Professor of Biomedical Engineering at Harvard University.