Goodbye tracking: why Uruguay is changing its strategy on close contacts

MONTEVIDEO.- The Ministry of Public Health (MSP) of Uruguay he told him “Farewell” to monitoring the epidemiological thread of Covid-19. The comprehensive contact tracing strategy of those who test positive for the novel coronavirus -and that the country had as a flag for over a year- now it was limited only to “big outbreaks” or to those that break out in prisons, retirement homes and other sensitive areas.

the the tetris system (test, follow-up and isolation) operated with relative success until december and, with ups and downs, he was on his feet until mid-March. But the strong community transmission of the virus led the health authority to modify the surveillance strategy. And the numbers reflect it.

The MSP had published an epidemiological report which revealed that as of April 10, Uruguay had a cumulative of 141,380 positive cases of Covid-19. In 47% of these cases, it was not known how they got the infection (either because there was no evidence of an epidemiological link or because the case had not been investigated). The data update, ten days later, shows that the cumulative positives stood at 167,033 and ignorance of the epidemiological thread reaches 55% of cases. That is: in the past ten days there have been 25,653 new positives and in 99% of them there is no information on how the virus was contracted. The sources of the health portfolio explained at The country that “due to the increased hiring of new trackers, case-by-case surveillance becomes unsustainable and the strategy followed by countries with high community transmission has been adopted.” In fact, some Montevideo trackers have gone inside to track specific outbreaks and have abandoned their old practice of calling the positives one by one and bringing the group of contacts together.

Biologist Matías Arim – one of the few Uruguayans with a post-doctorate in population dynamics and the study of epidemics – considers that “The abandonment of follow-up, due to greater saturation, is a serious strategic error.” Because? “It’s a way of letting the disease unfold in its maximum expression, instead of containing a part of it, however small it may be.”

Uruguay is one of the countries in the region with the greatest testing capacity. According to information published by the Chair of Infectious Diseases of the University of the Republic, with figures updated to April 17, Uruguay had 462,300 per million inhabitants, less than Chile and Panama .

“This enormous testing capacity, combined with monitoring, is helping to slow the epidemic. However, the test alone is of little use in diagnosing the specific case and in having some prediction of how much of the population will enter the ITC and the number of deaths, ”says Arim.

Insistence

The group of scientists advising the government (GACH) had insisted that it was necessary to lower the level of infections so that they did not exceed, on average, 200 positive cases per day. This is the threshold from which GACH understood that the epidemic would be under control, with community transmission at a second level of risk (today it is ranked fourth on the scale of the World Organization for health) and with the tetris strategy.

The MSP, for its part, has been able to maintain a certain level of monitoring up to figures of more than 200 cases per day, in particular after the incorporation of technology watch, the forms of which are filled in by the user himself.

There were countries that did not even attempt the strategy of containing the virus through testing, monitoring and isolation. In fact, in the international epidemiological literature, there is a discussion of whether Covid-19 is controllable. The flu is an example used in this debate: except when you get sick from it at home, who knows if you caught the flu on the bus or on your aunt’s birthday?

When the pandemic had just set in, it was clear to the MSP that travelers were more likely to have been infected than locals. Doctors, because of their high exposure, were more likely to be infected than a construction worker. And a prisoner, in an overcrowded cell, was more exposed than a rural worker in the middle of the field. When community transmission is very high, on the other hand, the chances of being infected are more homogeneous and the possibility of containment becomes less feasible.

In this direction, the current chances of knowing that a person has been infected in the workplace and not on a bus are very low. In addition, it becomes more difficult to detect that those who go to work and are asymptomatic are positive.

The Finnish company UPM is carrying out control tests on nearly 3,000 workers who build and operate the new pulp mill. They are daily and random. Thanks to this strategy and the size of its workforce, the analyzes serve as a mini-sample of what might be happening in the general population. When workers returned to work after tourism week, the company tested all of its staff and found 23 positive cases. Any of them were asymptomatic and would have gone unnoticed without this filter.

UPM now has 88 officials who pass through the Covid-19 infection. Many of them had previously had symptoms and were therefore diagnosed. But there have been 30 cases that learned of the contagion through testing at the pulp mill access and the results are known 95 minutes later. None of them would have known and this reflects the high level of community transmission. All of Uruguay’s departments are in the red zone, the highest level of epidemiological risk across Harvard University.

Last March, when the epidemic entered the maximum level of community transmission, the number of newly infected with Covid-19 increased by 80%. This growth has been such that the Ministry of Public Health ordered, at the end of this month, a test change: to replace the use of PCR tests with antigens.

The cost of these new tests is lower, but especially given the increase in the prevalence of the virus in the community, the predictive value of this type of test is better, the results of which are known in 40 minutes. (They are similar to pregnancy tests, although they are done with a pre-sample). The bet, however, has not been fully established. According to MSP data seen by El País, over the past week 114,399 tests were performed in Uruguayan laboratories and only 28% were for antigens.

Of course: when positive diagnostic test results are analyzed, the relationship is maintained (of the 23,215 positive cases last week, 29% were diagnosed with antigens).

The data are not less if one takes into account that the sensitivity of the test for asymptomatic cases is approximately 50%. This low sensitivity led the ministry to modify this week, on a proposal from the Chair of Infectious Diseases, the quarantine time between cohabitants who give negative results to the first tests.

Anyone living with a confirmed positive case should be tested for antigen as soon as possible.. If the result is positive, follow the same steps as any other confirmed (isolation for ten days or more depending on the clinical course).

If the result is negative, it is quarantined and another antigen test should be done between the fifth and seventh day after the last exposure. If the test is negative again, the attending clinician may find it necessary to perform a PCR test and will then remain in quarantine. Before this change, after a second negative antigen test, the partner was “released”.

The Country / GDA

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