A new study from the journal Nature has given one more reason to be extra vigilant against the Delta variant of Covid-19. The finding is that people with the variant can transmit the virus for almost two days before experiencing any symptoms. This has to be read together with the fact that presymptomatic transmission may account for nearly 75% of Delta variant infections. Vaccinated people with rare ‘breakthrough’ infections may also be able to transmit the virus as easily as unvaccinated people because of elevated viral loads. This change could be a key feature driving the most recent surge in Covid-19 cases, according to the study.
Presymptomatic transmission was a feature of the previous variants of the novel coronavirus, but the research suggests the gap between receiving a positive test to feeling symptoms was just 0.8 days. With the Delta variant, it’s 1.8 days. As a result, nearly three-quarters of infections with Delta happen during the presymptomatic phase, the research suggests. The Delta strain is more contagious, in part, because infected individuals carry and shed more virus than previous versions, observed Dr Stefen Ammon, medical director of the Covid-19 Task Force for DispatchHealth, an on-demand healthcare service. While the earlier version of Covid-19 was as transmissible as the common cold, the Delta variant is more transmissible than seasonal influenza, polio, smallpox, Ebola, and the bird flu, and is as contagious as chickenpox, he added.
Because of this increased transmissibility, Delta has become the dominant variant worldwide. It accounts for more than 90% of Covid-19 cases in the US. As Ammon recalled, when Covid-19 vaccines first became available, they demonstrated a great ability to prevent the recipient from contracting any form of Covid-19, which largely removed vaccinated asymptomatic and presymptomatic exposures from the equation. However, the Delta variant has developed an ability in some instances to partially evade the immunity provided by vaccination, meaning there are more breakthrough infections in vaccinated individuals from the Delta variant than were seen from previous versions of the virus.
However, experts contend that vaccines remain our best available tools to control the spread of Covid-19 and protect people from serious disease, hospitalisation, and death. Recent studies show the critical importance of getting the Covid-19 vaccine both for personal health and limited transmission. Dr Jason Gallagher, an infectious disease expert and clinical pharmacy specialist in infectious diseases at Temple University Hospital in Philadelphia, US, referred to two studies which show that the viral RNA declines more quickly in vaccinated people than unvaccinated people, suggesting that they are less likely to transmit virus to others.
These accumulated findings, along with the rapid rise in Covid-19 case numbers worldwide, have reinforced public health advisories from earlier in the pandemic. These include mask mandates, calls for physical distancing, and vaccination mandates — in many countries. All people, both vaccinated and unvaccinated, should wear masks while inside in public or crowded spaces, said Dr Elizabeth Beatriz, an epidemiologist at the Massachusetts Department of Public Health in the Bureau of Community Health and Prevention and a public health and Covid-19 adviser at Parenting Pod. This is particularly true if you are in an area where there are a lot of Covid infections, or you live with someone who is unvaccinated, including children, or someone who is immunocompromised, or who is likely to get very sick if they do become infected with Covid, she urged. In short, vaccination is the best protection.
