In an American prison, a 20-year-old man was infected with the coronavirus through brief but repeated exposure to inmates. As a result, the CDC suggested that the definition of what a close-contact is be reevaluated.
This is the story of a young prison employee in Vermont. In the course of his work, he came into contact with six inmates who were in his care. On July 28, 2020, the six inmates were waiting in a quarantine unit for their Covid-19 test results. They showed no symptoms. The prison guard was in contact with them only for a few minutes, but a few days later, on August 4, he suffered a loss of taste and smell, muscle pain, and breathing difficulties. Everything seemed to point to Covid-19, his test came back positive the next day. All six inmates also tested positive. How was the 20-year-old employee infected? The Center for Disease Control and Prevention (CDC) reported this particular case in a notice published on its website.
Short but repeated contacts
To find out how the 20-year-old employee was infected, the CDC used the prison’s surveillance cameras to see if his interactions with inmates can be characterized as “close contacts” – is less than two meters from a person for more than 15 minutes. None of his visits to inmates meet these criteria. However, the investigation assumed that at least one of the asymptomatic inmates infected the prison staff because he had no contact with Covid-19 patients outside of work.
On the other hand, surveillance cameras showed that the employee was 22 times less than two meters away from the inmates during his shift. Although each interaction did not last more than one minute, he still spent about 17 minutes in contact with them. This was enough time for the virus to infect him.
In most interactions outside their cells, inmates wore masks, but in some cases, especially in the prison yard, they did not wear them. The employee himself wore a mask, goggles, and gloves. The preferred route for SARS-Cov-2 to spread is direct contact even if these contacts are brief; the probability of contamination increases significantly if they are repeated. The use of protective equipment does not protect a healthy person 100%, especially if an infected person is not wearing protective equipment.
Refining the definition of a contact case
Until now, for its contact tracing the CDC only considered those who had been close to a Covid-19 patient for over 15 minutes. These individuals are then identified as at risk of developing the Covid-19 and transmitting it. After this episode, it seems clear that close contact parameters are more complex than what was previously thought.
Proximity, duration, symptomatic or asymptomatic state, the environment in which contact took place and the production of aerosols are parameters that must be taken into account in order to effectively trace those that are more likely to spread the disease unconsciously.