The study on the prevalence of coronavirus led by the University of Tartu reveals that every 40th adult in Estonia is infectious. About one fifth of the adult population has developed coronavirus antibodies. The large proportion of asymptomatic virus carriers and the underestimation of exposure to the infected makes the situation even more complicated.
From 11 to 22 March, 2,386 random-sampled adults were tested and in 2,252 of them, also the number of coronavirus antibodies was analysed. The results showed that 102 people (4.1%) gave a positive PCR test. 41 of them (40%) had recovered from the disease and were no longer infectious. However, 61 people (60%) who tested positive were still infectious. Therefore, it can be estimated that an average of 26,500 people (2.5%) of the adult population may be carrying and spreading the virus.
According to the head of the study, Professor of Family Medicine at the University of Tartu Ruth Kalda, the most concerning aspect of such an extensive spread of the virus is the fact that nearly half of the infectious PCR-positives do not have any symptoms. “This means that they are not aware of their infection and therefore do not know that they should isolate themselves. Since there are more people infected than ever before, one may be exposed to the virus anywhere. The best way to prevent the spread of the virus is to avoid close contacts,” Kalda explained.
The study on coronavirus antibodies conducted in the framework of the prevalence study revealed that antibodies have developed in an estimated average of 229,000 adults, i.e. 21% of the adult population. Half of them have developed antibodies by suffering from the disease, and half by vaccination. During the past month, the number of people with antibodies has increased the most by those who have received the first vaccine dose.
Although a large number of people who have developed coronavirus antibodies have got them by suffering from the disease either knowingly or not, Kalda says that it is yet unknown how long the protective bodies thus formed will last. “To achieve longer-lasting virus protection and the security of society as a whole, the widespread vaccination of the population will give the most reliable result. Therefore, the current guidelines also recommend vaccinating those who have suffered from Covid-19 with one dose one week to six months after recovery,” Kalda explained.
Level of caution is increasing, but many still do not change behaviour after close contact
The behavioural study confirms that the extensive spread of the virus and stricter movement restrictions have had their effect. More people avoid physical meetings and social gatherings even in small groups, observe the safe distance rule and refrain from travelling beyond county boundaries. This can be seen among the younger and older adults alike.
One in ten adults is believed to have been in close contact with an infected person. Compared to the study wave conducted a month ago, there has been a slight decrease in the number of those who continue their daily activities after close contact, but still about one fifth of people do. “Including those who change very little in their everyday activities after close contact, we can see that about half of people are not bothered by a probable close contact. This provides very favourable conditions for the virus to continue spreading,” said Kalda.
The study on the prevalence of coronavirus is carried out by a broad-based research group of the University of Tartu in cooperation with Synlab Eesti, Medicum and Kantar Emor.
For more information about the study, see the University of Tartu web page.
Further information: Ruth Kalda, Head of the Institute of Family Medicine and Public Health, Professor of Family Medicine, 5698 5599, ruth.kalda [ät] ut.ee