Coronavirus: a tiny drop of saliva is enough to infect another person

The coronavirus spread from China to the world in 2019 and is still spreading. One of the advantages it has had is its contagiousness, which was greater with the different variants of concern that were generated. A study in the UK found that only a 10 micron drop of coughing or sneezing is enough to infect a person with the coronavirus.

It was discovered through a controversial study that he infected a group of 36 people who volunteered with the virus. The objective of the study was to understand how infection occurred in people who were exposed to the coronavirus. It was led by researchers from the Imperial of College and featured in the journal Nature Medicine.

He also revealed that it takes only two days for a person who gets the infection to start spreading the virus to others. In addition, more evidence was found on the pre-symptomatics that they contagious: infected people eliminate a large number of viruses before showing the symptoms.

The trial consisted of infecting 36 people with the coronavirus who were monitored for up to two weeks after their stay in the hospital in March 2021. Then, they followed up on their evolution. Not everyone got the virus even though they were exposed.

The 36 volunteers were between 18 and 30 years old and had no risk factors for severe Covid-19 and were infected with a small drop of liquid containing the original strain of coronavirus. As a precautionary measure, patients were infected in stages. The first 10 people received the antiviral drug remdesivir to reduce their chances of serious illness, although it was considered unnecessary.

The researchers monitored patients 24 hours a day while they stayed for two weeks at the Royal Free Hospital in London. Of the 36 patients, 18 were infected. Two of them never developed symptoms.

Those who were ill had mild cases of nasal congestion, congestion, sneezing, and sore throat. None of the patients developed lung problems, possibly due to their good health or the fact that they were given small amounts of virus.

About 83% lost their sense of smell, at least partially. Six months after the completion of the study, a person has not yet recovered his sense of smell, but he is getting better. The study volunteers expelled virus for about 6.5 days, on average, or up to 12 days, even if they had no symptoms.

Professor Christopher Chiu, from Imperial College London, was the leader of the research. “Our study reveals some very interesting clinical ideas, especially around the short incubation period of the virus, the very high viral excretion through the nose, as well as the usefulness of lateral flow tests, with possible implications for public health,” he clarified.

The researchers also did cognitive tests to verify the volunteers' short-term memory and reaction time, although the data are being evaluated. The study volunteers expelled virus for about 6.5 days, on average, or up to 12 days, even if they had no symptoms.

After knowing the results of the study, there are different perspectives. Miles Davenport, an immunologist at the University of New South Wales in Sydney, Australia, considered that “it represents a potentially important step forward in the way we evaluate the effectiveness of future vaccines and drugs. This opens up a number of important possibilities for studying immunity in a controlled environment.”

However, some researchers wonder whether the knowledge gained by the study so far is important enough to justify the risks to participants, such as the possibility of long-term side effects. “In my opinion, it is still not entirely clear whether these studies are ethically justified, and I am waiting to see what else they have found,” said Seema Shah, a bioethicist at Northwestern University of Chicago, in Illinois, United States.

T he studies of exposure to controlled infection have been used for decades to study influenza, malaria and numerous other infectious diseases. Some researchers advocated conducting such trials with the coronavirus in the first months of the pandemic, as a way to accelerate vaccine development. But others felt that such trials were too dangerous to be acceptable, when so little was known about the virus and few effective treatments were available.

The trial was supported by a commercial clinical research organization based in Dublin called Open Orphan and its London subsidiary HVivo. Volunteers received £4,565 ($6,200) for their participation, which involved at least two weeks of quarantine in a high-level isolation unit at the Royal Free Hospital in London.

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