El Mundo (Spain): asymptomatic carriers of coronavirus infect other people as well as those who have obvious symptoms

The virus, the media has no symptoms, is much harder to detect and therefore to deter its spread more difficult. Although many scientists are virtually unanimous in the view that asymptomatic patients may spread the SARS-CoV-2, there are still doubts about the impact of the “bessimptomnogo” on the scale of the pandemic. According to a recent study conducted in the Italian municipality (urban community) In these patients play an important role in the transmission of the novel coronavirus. Within a few weeks of quarantine to the study authors, scientists, University of Padova and Imperial College London, surveyed the majority of residents of the commune In. They published the results of their study in the journal Nature.

In this small municipality in the region of Venice is home to about 3,200 people. It was there that February 21 was the first recorded death from covid-19 in Italy. As a result of 14 days was introduced a state of isolation. During this period, scientists were able to take the tests almost all the inhabitants of the commune In (first in 86%, as a result, 72%) and with maximum accuracy to determine how the virus spread: in the early days of the infected was 2.6 percent of the population. Two weeks later it dropped to 1.2% (29 people). The study authors emphasize that a combination of tests, isolation of infected and regime isolation really helped stop the outbreak.

In addition, they note that approximately 40% of those infected do not have symptoms, and this rate was almost unchanged during the period. This figure corresponds to the models previously developed in Hong Kong, Singapore and China, according to which 30 to 60% of all infected have no visible symptoms. “Despite invisible and ubiquitous spread of the disease, it can be controlled,” — says Professor, Department of molecular medicine of the University of Padua and the faculty of biological Sciences, Imperial College, the main co-author in the journal Nature Crisanti Andrea (Andrea Crisanti). “Our research proves that if you do the tests to all citizens regardless of whether they have symptoms or not, it is possible to successfully contain the spread of the disease and maintain control.”

However, none of the children under 10 years of coronavirus was not detected despite the fact that many of them lived in families where there are infected. “Still many questions concerning transmission of the virus SARS-CoV-2 remain open. For example, what is the role of children and the impact on the chain of infection have asymptomatic carriers,” adds Dr. Dorigatti Ilaria (Ilaria Dorigatti) from Imperial College London. “It is extremely important to find answers to these questions, to use appropriate control strategies and, thus, to prevent the spread of coronavirus”.

Without clear criteria

Most health authorities have understated in their reports, the risk of transmitting the virus to asymptomatic patients, prompting criticism from the scientific community. A few weeks ago technical lead in responding to the pandemic, the world health organization (who) Maria van Kerkhove (Maria Van Kerkhove) stated that asymptomatic patients are “very rare” become sources of infection. The next day she had to clarify what she meant: it referred to “a misunderstanding” and explained that “we are working to gather information” on this topic. Similarly, when a few days ago, a Spanish epidemiologist Simon Fernando (Fernando Simón) asked about the outbreaks of disease that appeared in Spain in recent weeks, he said that 60% of those infected in the country is the asymptomatic patients who “practically do not contribute to the” transmission of the virus.

However, according to the Italian study, viral load, i.e. total number of viral particles in the human body, in asymptomatic patients the same as all other patients. Therefore, asymptomatic carriers and those who have no obvious symptoms, can greatly contribute to the spread of covid-19. Especially when because of lack of symptoms infected do not observe precautions, not knowing that they are carriers of the virus.

“If the viral load of patients with symptoms and without them comparable, so even asymptomatic carriers of the virus may contribute to its spread. We confirmed this by restoring the chain of infection and track all contacts of infected in the commune In. However, we do not yet know fully how strong is the impact of the symptoms. We know that when a person coughs or sneezes, the air gets considerably more virus particles. But at the same time, patients with symptoms more likely to limit the number of their contacts than people who have no symptoms,” explains Dorigatti.

The results of this analysis from the very beginning served as a basis for developing community measures in the area of Venice, where all who came in contact with an infected could pass the test for the coronavirus. “Research proves that early detection of infected and timely isolation of patients with symptoms and without them can prevent infection and keep the epidemic at an early stage,” says Crisanti. “Today, this is particularly important given the risk of new infections and the second wave of the epidemic”.