While the world is still battling to control coronavirus infections nearly two years after the pandemic began, one study indicates that it may be possible for societies to keep Covid-19 cases low and levels controlled over the long term with strategic use. diagnostic testing, contact tracking, and policies to isolate the infected.
These strategies would partially compensate for the events of local spread of the virus, and only moderate restrictions would be needed, the authors propose. On that balance, daily new cases would stabilize at about ten infections per million people or less.
For reference, in Brazil, the moving average of new cases in seven days registered last Thursday was 71 cases per million inhabitants. In the same week, the country had a moving average of 438 deaths a day, the lowest in 11 months.
The research used mathematical modeling to simulate the long-term results of Covid-19 numbers based on different parameters. The study was conducted by a team of researchers from the Max Planck Institute for Dynamics and Self-Organization (Germany) and published in the journal Science Advances on Friday (8).
The stability of the number of infections can be impaired, however, if restrictions are reduced or if cases increase significantly. When mitigation measures are insufficient, contagions can exceed the limits of the local capacity to test, trace and isolate. When this happens, health authorities are no longer able to track contacts and discover chains of infection efficiently, and therefore controlling the spread of the virus becomes more difficult.
In this case, the researchers concluded that a four-week lockdown can restore control of the virus without the need for repeated lockdowns.
“In our scenario, a lockdown lasting four weeks is enough to achieve the stable regimen. However, if it is suspended too soon (before the four weeks are up), the number of cases will rise again shortly thereafter”.
The research further indicates that repeated lockdowns are not necessary to maintain control over the spread of the coronavirus if a moderate reduction in person-to-person contacts is maintained while the numbers are within testing, screening and isolation capabilities.
The authors argue that this control strategy, which aims to keep Covid-19 numbers below the capacity threshold for testing, screening, and isolation, is better than a strategy that focuses on keeping numbers below the capacity threshold. of hospital care. According to them, the model they propose would require fewer contact restrictions (in the long run), have a shorter lockdown duration, and cost fewer lives.
In addition, the long-term strategy to keep Covid-19 levels low, without imposing as many restrictions on people-to-people contact, would have benefits for public health, psychological well-being and the economy, the authors say.
“This strategy reduces cumulative cases (and fatalities) four times more than strategies that just prevent hospital collapse. In the long run, immunization, large-scale testing and international coordination will further facilitate control,” says the article.
The research was completed in December 2020, when coronavirus vaccination campaigns around the world were just beginning. Researchers say the proposed strategy is independent of the availability of vaccines or a cure. Still, according to them, vaccination campaigns should facilitate the success of this strategy to contain new waves of contagion.
Model
To explore the long-term strategies societies can use to keep coronavirus infections at low levels, the researchers modeled the spread of the virus in different scenarios. They used an epidemic model called SEIR that divides the population into four compartments: susceptible, exposed, infectious and recovered.
The model took into account both infected individuals who were quarantined and those who did not isolate themselves, and followed a framework in which individuals with symptoms have a preference to test themselves, their close contacts are also tested, and a random screening of asymptomatic individuals is made in the general population.
When the researchers simulated vaccination scenarios for the European Union, they found that the decline in the number of cases of the disease could be achieved several weeks in advance if daily new cases were kept below the threshold of testing, screening and isolation capacity.
Test – Tracking – Isolation
In the proposed strategy, people are tested – and quarantined if the test is positive – through three mechanisms: first, people with symptoms of Covid-19 would report their case or be identified through surveillance, with a preference for a test .
Second, random testing would be done on asymptomatic people in the general population. Third, all close contacts of people who test positive on these two mechanisms would also be tested.
Contact tracing of people who have tested positive for coronavirus is intended to break the chain of transmission, because people eventually infected can quickly begin self-isolation.
In countries where contact tracing is done, health teams contact individuals diagnosed with Covid-19 and ask questions about where the person has been and with whom they have had contact. The teams then call these contacts to advise them on symptoms of the disease, where to get tested, and other measures to prevent transmission of the virus.
Quick tests to fight the pandemic
Several countries are betting on the wide availability of diagnostic tests and using contact tracking systems for those infected to control the spread of Sars-CoV-2.
Rapid antigen tests have helped to reduce the spread of the coronavirus across Europe. United Kingdom, France and Germany are some of the countries where these tests are easily found, in many cases free of charge.
In Germany, since March of this year, rapid tests have been available to the population free of charge, financed by taxpayers’ money. People who are not vaccinated could find the tests in different parts of cities to use them as proof that they do not have the disease and thus access various establishments, such as cinemas, gyms, schools, cultural events and indoor areas of restaurants.
However, from this Monday (11), most Germans will have to pay for the tests. The decision, by the German government and the governments of the country’s 16 states, aims to encourage vaccination. Rapid tests will still be free for children under the age of 12, who cannot yet receive the vaccine, and for people who cannot be vaccinated for medical reasons. PCR tests, when requested by doctors, will remain free to all.