It is estimated the contribution of asymptomatic carriers in the spread of the coronavirus
North American scientists have built a model of the transmission of the new coronavirus taking into account the asymptomatic carriers. It turned out that without accounting for and control of this category of infected to fight off the infection is unlikely to succeed. The study is published in the journal Proceedings of the National Academy of Sciences.
Since COVID-19 worldwide was introduced unprecedented restrictions on movement and measures of social distancing. The consequences for the economy of many countries was very serious. In addition, in some places there were social protests led by the measures limiting personal liberty.
While there is still no clear answer how effective was the quarantine measures, and what should be the optimal strategy to limit the spread of the virus through the next wave.
Scientists from the U.S. and Canada in the new model estimated on the basis of the latest data the contribution presentano and asymptomatic transmission and came to the conclusion that even the isolation of all persons with symptoms of the disease may not be sufficient to suppress outbreaks of the disease, because concealed carriers are responsible for more than 50 percent of transfer cases.
The first simulation was conducted with such detail. The entire population was divided into nine categories: susceptible, incubation period, presentatie, asymptomatic, symptomatic with mild or severe disease, recovered and dead, and for five age groups. The number of daily contacts was determined by the matrix of contacts made separately for each age group.
According to the simulation results, in order to keep the incidence of COVID-19 less than one percent of the population, and this is the goal of epidemiologists, need to was discovered and isolated at least one third of asymptomatic carriers, the proportion of which is from a 17.9 to 30.8 per cent of all infected.
Even if the minimum value is 17.9 percent, according to scientists, the share of asymptomatic carriers accounting for 3.4 percent of all transmission of infection, while the share of preasymptotic 48 per cent.
"Empirical studies have shown that people can be the most contagious during presentano phase, which is an unusual characteristic for respiratory infections," write the authors.
The researchers concluded that to effectively combat coronavirus infection and prevent the risk of her return to the national regime of restrictions and isolation of infected must be supplemented with control measures, contact tracing and testing of individuals without signs of disease.
To stop the spread of coronavirus, according to the authors, it is necessary to expand the program of mass testing, as well as to introduce a system of monitoring all contacts with patients, irrespective of symptoms.
Scientists believe that these programmes and systems should be available this fall, when the background of the wave of seasonal flu in the Northern hemisphere coronavirus, first, aktiviziruyutsya, and secondly, it will be difficult to unequivocally identify without testing these two similar in symptoms.