US Scientists Have Calculated The Number Of Coronavirus Particles In Asymptomatic And Regular Patients
Approximately 32 thousand asymptomatic carriers of SARS-CoV-2 and patients with an obvious form of coronavirus infection had approximately the same number of viral particles in their bodies. These conclusions were reached by American scientists, whose preliminary research results are available in the electronic scientific library medRxiv.
"Our observations show that at the peak of the epidemic, the concentration of viral particles in the body of both patients was equal. However, after the number of new infections began to decrease, it was somewhat less in asymptomatic patients. All this suggests that conventional RNA tests are well-suited for finding asymptomatic SARS-CoV-2 vectors and evaluating their number," the scientists write.
At the end of January, the head of the state health administration of China, Xiaowei MA, said that a new type of coronavirus (SARS-CoV-2) might be transmitted from person to person even before the first symptoms of the disease appear. Later, epidemiologists from many countries came to a similar conclusion.
Initially, the scientific community as a whole was skeptical of such statements. However, observations have confirmed that this is possible. For example, in June, doctors found that more than 40% of infections in one of the epicenters of COVID-19 in Italy occurred before the carriers showed symptoms of coronavirus infection.
Because of this, scientists are investigating in detail how asymptomatic transmission of the virus occurs. This is necessary to assess how often this happens and how dangerous it is. A group of doctors led by Professor Eric Lander of the Massachusetts Institute of Technology (USA) took a big step towards solving this problem. In the new work, they measured the typical concentration of viral particles in the body of asymptomatic patients.
This study was conducted among residents and employees of nursing homes in Massachusetts (USA). As a rule, residents of such institutions are most vulnerable to coronavirus infection due to age, chronic diseases, and the fact that they live relatively compactly.
Based on similar considerations, the state government in April-June of this year began mass testing for COVID-19 for all residents and employees of such nursing homes. Authorities continuously monitored possible SARS-CoV-2 outbreaks and its distribution pathways. These data were used by scientists to find out how often the infection occurred without symptoms and how it was tolerated by patients.
In total, more than 15% of the elderly residents of boarding houses, about 2,650 people, and 620 of their employees (4%) were carriers of the coronavirus. The infection was asymptomatic among 70% and 92% of them, respectively. The concentration of viral particles in both groups was approximately the same. Over time, it changed in a similar scenario for representatives of all age groups.
Interestingly, these indicators began to diverge at the end of May, when the COVID-19 outbreak in Massachusetts went down. Scientists do not yet know what this is related to. However, they suggest that the reason for this was that in most symptomatic patients, the virus was found at the moment when the concentration of SARS-CoV-2 particles reached a peak.
All this, according to Lander and his colleagues, suggests that both types of virus carriers are equally dangerous to others during the peak of the epidemic. This should be taken into account when assessing the rate of spread of the coronavirus and when planning measures for further control of COVID-19.
It's worth noting that the article of scientists was not reviewed by independent experts and not checked by the editors of scientific journals, as is usually the case in such cases. Therefore, conclusions from it and similar articles should be treated with caution.