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People who have the symptoms most frequently associated with covid-19 (fever, cough, or shortness of breath) are not the ones with the most positive diagnoses. By contrast, the highest proportion of positive tests occurred among people who never manifested any symptoms or had contact with suspected or confirmed cases of covid-19, according to the latest study report. Pandemic diaries, an initiative of the Public Health Institute of the University of Porto (ISPUP) and the Institute of Engineering, Technology and Systems and Computer Science (INESC TEC), which has the support of the PUBLIC.
“For each symptomatic case, there will be four, five or perhaps more cases of infection that do not present symptoms,” concludes Henrique Barros, president of ISPUP, a public health specialist and epidemiologist, in a reading of the results of the surveys carried out on a sample. (dynamic and not representative of the population) of 11,125 individuals. Of these, 8,613 people reported that they had never had personal contact with suspected or confirmed cases of covid-19, nor developed any symptoms. Still, if they had a higher perception of risk or because they used public transport more, for example, 187 decided to take the SARS-CoV-2 test and almost half (48.7%) were infected.
“It is true that the test can be falsely positive and even with a higher frequency than desired in ‘real life’ conditions that differ from ideal laboratory situations,” begins Henrique Barros’s emphasis. For the epidemiologist, however, the most plausible lesson from these numbers is that the number of infected people among the Portuguese population is much higher than the confirmed cases. “Official figures are based on symptomatic cases, and are now beginning to be ‘contaminated’ by asymptomatic cases due to detection. [nos lares de idosos e nas creches, por exemplo]. But it is obvious that we cannot examine the entire population ”, he contextualizes.
Still, the epidemiologist argues that the country should be more liberal in conducting these screening and diagnostic tests. “At first, we were much more critical and selective with the tests, based on what we knew about the coronavirus and the availability of the tests, which was lower, but it is important that we are now much more liberal. If we do more tests, we will find more positive people and this will contribute to “better maintain” the transmission chains, “he defends.
Even so, Henrique Barros does not believe that when the health authorities begin to Testing the immunity of the population through serological tests that detect the presence of antivirus, which should happen in the coming days, we can find high levels of immunity. “I don’t think what can happen here happened in New York, in the United States or in some cities in Lombardy, in Italy, where the contact chains were brutal and, therefore, the proportion of people infected without symptoms is very high . I would risk saying that we will be below 2% nationwide, ”he anticipates, admitting that the values may be slightly higher in cities such as Lisbon, Porto and Gaia, where there are many confirmed cases.
Symptom overvaluation
Among the more than 11,000 respondents, 2,512 people reported having symptoms such as cough, fever, and shortness of breath and / or contact with people suspected or infected with the coronavirus. Despite this, only 282 were for the diagnostic test. At a more microscopic level, among the 295 people who added recognized risk cases to their contacts, only 73 did a test. Why “One reason is that, in the initial phase, having symptoms was not enough to be able to be tested. It was necessary to have the call link epidemiological If the person had not left the country or had been with someone who had come from Italy, they would order him to take ben-u-ron and stay home, “remembers the ISPUP president.
On the other hand (in clear contrast to the 48.7% of positive cases detected among asymptomatic people without any known contact with infected people), among the 282 people who had symptoms or “risky” contacts, the proportion of positive results was less than Expected: 37% for those who had symptoms and contacts, 21% for those who only had symptoms, and finally 32.5% for those who had contact with suspected or confirmed cases of covid-19.
Possible explanations? There is also a risk of “false negatives,” but it was not because “when the symptomatic person was tested, they had passed the stage where they were excreting the virus.” But Henrique Barros admits that many people have overestimated the symptoms that led to the test. “As far as they’re concerned, people may be evaluating any cough that, perhaps, is worthless. The feeling of shortness of breath is also subjective: anxiety causes shortness of breath. Fever is more difficult to assess subjectively, but it can also have a psychogenic component, “adds the public health specialist, to conclude that” the perception of individual risk may not be a good advisor in these cases. “
Less educated people try more
The study Pandemic diaries It also allowed detecting social gradients among people who decide to be tested for coronavirus infection. Among the 469 respondents who carried out at least one infection test, in a proportion of 4.2%, slightly higher than the 3.1% described so far for the total Portuguese population –, there are more women than men, especially in the so-called “middle ages”. On the other hand, there were more people looking to take the exam among the less educated. Among doctorate holders, the proportion of those who took the test was 2.5%, compared to 4.1% of those with a secondary education or less.
“The more educated, the more people are at home in telecommuting and the less risk they feel. We already knew from previous samples that people who perceive more risk do more tests and that There is a clear relationship between leaving home and the fear of being infected, “emphasizes Henrique Barros, to reinforce that” people who traditionally have less differentiated professions and a lower level of formal education tend to be more afraid, probably because they feel that they won’t have the literacy to really measure the risk. ”
On the other hand, and as expected, it evaluates more those who have professions related to health and social support. The good news here is that “the frequency of positive tests was significantly less” among these professionals. “This shows that, even in situations of higher risk exposure, knowledge and the application of preventive measures lead to a lower risk of contracting the infection,” the study concludes.
