We know that when you are infected with the Sars-Cov-2 coronavirus, you can start transmitting it to those around you even before the first symptoms appear. Thus, according to a study published by Public Health France in July 2020, a quarter of coronavirus cases are asymptomatic and the potential for transmission of the virus is maximum 2 to 3 days before the appearance of symptoms of Covid-19.
This time a study published in Jama indicates that carriers of the virus who remain asymptomatic also play a major role in the transmission of the virus. Indeed, according to this study led by Professor MichaelJohanssonHarvard Center for Disease Control and Prevention (CDC) more than half of the cases of transmission would be due to asymptomatic carriers. A not very reassuring discovery because it means that identifying and isolating people with symptomatic Covid-19 will not be enough to control the continued spread of SARS-CoV-2.
“These results suggest that measures such as wearing masks, hand hygiene, social distancing and strategic testing of people who are not sick will be essential to slow the spread of COVID-19 until safe and effective vaccines are available and widely used,” say the researchers.
Without symptoms, contagiousness would be lower
The Singapore researchers estimate, for their part, that contagiousness is less when there are no symptoms. According to their study, published in The Lancetasymptomatic covid patients would be four times less contagious than patients who show symptoms of the disease.
To reach this conclusion, the researchers followed the contact cases who completed their quarantine between August 1 and October 11. By distinguishing between contact cases of asymptomatic people and contact cases of symptomatic people, they realized that the former had 3.5% risk of being contaminated while the latter had 12.8% risk.
A patient with Covid-19 asymptomatic for 70 days
British and American researchers have reported the case of a 71-year-old woman, infected with the Sars-Cov-2 coronavirus, and remained asymptomatic for… 70 days. In February 2020, the immunocompromised septuagenarian (affected by chronic lymphocytic leukemia (CLL) for 10 years) presented to the Emergency Department with pain in the lower back and lower limbs. Operated on February 14, 2020, she was re-hospitalized on February 25, 2020 due to severe anemia. On February 28, 2020, the patient presented no respiratory or systemic symptoms (fever, body aches, etc.).
As explained in the researchers’ report, published on March 4, 2020 in the specialized journal Cell, the patient was diagnosed positive for Covid-19 on March 2, 2020. Placed in isolation, she was re-tested 14 times: on June 15, 2020, she was still positive for Covid-19… Finally, on the 16 June 2020, the patient was declared “negative” for Covid-19. She never had any symptoms.
“Although it is impossible to extrapolate from the case of this single patient, our data suggest that persistent Covid could reach some immunocompromised patients – suffering from cancer, for example.“, write the scientists.
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