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Asymptomatic cases of COVID-19 addressed in Cuba’s strategy to reduce the risk of infection

CUba covid pcrOver the past six months, the country has worked tirelessly to contain the COVID-19 epidemic. Our scientists, health authorities, and government have spared no effort to stop a highly contagious disease, that proliferates and kills if any precautionary measure is overlooked. The SARS-COV-2 virus is spread by contact with droplets that are expelled from the mouth and nose of an infected individual – including those exhibiting no symptoms – when coughing, speaking, or simply breathing.

Precisely to share information and raise risk perception, Granma spoke with Dr. Vivian Kourí Cardellá, first deputy director of the Pedro Kourí Institute of Tropical Medicine (IPK), to learn more about the impact of the large number of asymptomatic cases of the disease.

“An asymptomatic person is defined as someone infected with a pathogenic agent, who does not present manifestations of the disease. When a diagnostic test is administered, the result is positive and the individual can transmit the infection to others,” she explained.

Dr. Kourí, a microbiologist specializing in virology, added that in the case of SARS-COV-2, contagion is determined through a PCR test in real time, using a nasopharyngeal exudate sample.

“It is important to differentiate between asymptomatic and pre-symptomatic individuals. It may be that the patient is tested at an early stage and subsequently develops the disease. Such cases are not considered asymptomatic, since this group includes only those who never show any type of symptom,” she stated.

The scientific literature reports that this phenomenon occurs in 40% to 70% of cases confirmed, especially if health authorities are conducting population studies to detect outbreaks or local transmission events in a given area.

This is, in fact, the strategy Cuba has implemented since the appearance of the first imported cases, March 11th, with immediate hospitalization of the sick, as well as testing and isolation of their direct and indirect contacts – producing an average rate of asymptomatic cases close to 60%.

-Is the viral load of an asymptomatic individual higher than that of a person exhibiting symptoms?

-There is no scientific evidence on this matter. Cuba does not have conclusive data on the subject either. Current investigations report differences, between symptomatic and asymptomatic individuals, in the duration of positivity in Polymerase Chain Reaction (PCR) tests. In antibody tests (to determine if the body has produced an immune response to infection), it has been noted that antibodies increase earlier, with higher titer, and last longer in symptomatic patients, as compared to asymptomatic individuals.

-What treatment is recommended for asymptomatic individuals, in addition to isolation?

-Around the world, asymptomatic patients do not receive any type of treatment, they are simply told to isolate themselves at home and limit contact with others.

In Cuba, such individuals are given medications to boost the immune response, such as interferon and nasalferon. The latter is a chemical compound administered through the nose, which is less invasive, with less risk for the body.

-What procedures are performed to determine if a person is infected with the virus?

-A person who arrives with respiratory symptoms is hospitalized, evaluated and isolated in a center for suspected cases, and a sample of nasopharyngeal exudate is taken. If a positive result is produced, the person is classified as a patient with COVID-19 and is transferred to an institution that provides specialized treatment of the disease. If the result is negative, the person is referred to a non-COVID center.

The confirmed case generates a contact study, and isolation of all relatives and friends. Focused studies are also conducted among the population where the person lives and works, to determine the degree of transmission. The most distant contacts are followed by primary care physicians in the area.

Testing of those sent to isolation centers is conducted five days after the last contact with the confirmed patient. If the test is negative, a second test is repeated after another five-day interval, during which the individual stays at home and has no contact with others in the community. This group is kept under epidemiological surveillance, since the virus has an incubation period of up to 14 days.

With this second test, we can identify asymptomatic individuals carrying the virus. Those in this group are isolated in centers established for asymptomatic cases.

-Are PCR tests expensive?

-Cuba does not produce PCR diagnostic tests. We purchase them abroad. We produce only a limited volume of expendable materials, I am referring to swabs for sampling, the collection medium, where the swab is placed and other items. We also produce personal protection wear, that is clothing.

What we cannot produce are the reagents. These supplies are obtained abroad, at a price of approximately 50 dollars per test. This does not include the cost of medical care, transporting the samples or handling them in laboratories.

Large laboratory companies sell these reagents, which are very expensive, and are currently in short supply.

The country faces many obstacles in purchasing these reagents, even with the money in hand, for this purpose.

-Can Cuba produce the supplies needed to administer PCR tests?

-Several BioCubaFarma centers are investigating the possibility of producing the reagents and inputs for the laboratory. We have sought to reuse the plastic materials.

The literature suggests discarding all the material used in molecular biology work, but we are experimenting with a type of protocol for washing and sterilization with autoclaves and radiation. Thus far, we have seen encouraging results.

-Estimating more than 7,000 tests a day, at $50 a piece, since the beginning of the pandemic, means an expense of millions…

-The country is investing a great deal of money in these diagnostic tests, and this represents a huge effort for an underdeveloped nation like ours, which is economically blockaded by the United States government, as well.

The expense is warranted, because we are talking about an epidemic that is very difficult to contain, with a high number of infections and deaths. As long as a vaccine is not available, unfortunately, there will be no effective, worldwide control of the epidemic.”

(Source: Granma)

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