People affected by the Delta variant of the SARS-CoV-2 coronavirus appear to develop more severe forms of the disease than those affected by previous variants. The Delta variant also spreads just as efficiently as chickenpox, according to an internal CDC document, data from which will soon be released.
Spread in 132 countries, the Delta variant is now implicated in the vast majority of new infected cases. The researchers were well aware that this variant was particularly virulent compared to the others, but they could have largely underestimated its power of contamination. An internal Centers for Disease Control and Prevention (CDC) document obtained by The Washington Post on Thursday, July 29, indeed reveals the scale of the challenge facing global health agencies.
As a reminder, the reproduction rate of a disease gives a rough estimate of the number of people to whom an infected person can transmit the disease. The original Sars-CoV-2 coronavirus was first estimated to have a reproduction rate of around two or three. According to the CDC document, the data of which will be published in a few hours, the Delta variant will be up to four times more contagious than this .
It would thus be more transmissible than the MERS, SARS, Ebola, smallpox and seasonal flu viruses, and just as contagious as chickenpox.
"I'm done reading it [the report]much more concerned than at the beginning “, writes in particular Robert Wachter, president of the department of medicine of the University of California in San Francisco, in an e-mail sent to WP. "I think people need to understand that we're not crying wolf here. This is serious “, adds to CNN Rochelle Walensky, the director of the CDC who confirmed the authenticity of the document. "It's one of the most transmissible viruses we know of “.
It's not over. The Delta variant would also be more likely to break down the protection provided by vaccination. If so, its transmission rate would therefore be less affected by the vaccination status of its host. “The key takeaway is that vaccinated people, even though they had no symptoms, were infected and shed the virus at similar levels to unvaccinated people “, explains Walter Orenstein, of the Emory Vaccine Center, who had access to the documents.
“I think the central problem is that vaccinated people are probably involved to a large degree in the transmission of Delta “, also writes Jeffrey Shaman, an epidemiologist at Columbia University. “In a sense, vaccination is now a matter of personal protection:protecting against serious illness ". On the other hand, the extreme contagiousness of the Delta makes herd immunity a more difficult target.
Despite everything, the report confirms the importance of getting vaccinated. Although infection transmission rates may not have been reduced, the risk of developing severe disease or dying from this disease for vaccinated people is still less than one-tenth that of people unvaccinated.
Furthermore, if this variant is indeed more likely than the original virus to infect you even if you have been vaccinated, your risk of infection is still reduced d a factor of three compared to a person who has not been vaccinated.
