WHO officials are puzzled and trying to unravel why the delta variant of the coronavirus is more transmissible and potentially makes people sicker than the original strain. Dr Maria Van Kerkhove, WHO’s technical lead on COVID-19, told a press briefing that they are trying to better understand the delta variant as it’s a “threat”.
She explained that there are certain mutations in the delta variant that, for example, allow the virus to adhere to a cell more easily. “There is some laboratory studies that suggests that there’s increased replication in some of the modeled human airway systems.”
The Centers for Disease Control and Prevention (CDC) warned that new research indicates the delta strain is more contagious than swine flu, the common cold and polio. It is as contagious as chickenpox. The variant also has a longer transmission window than the original COVID-19 strain and may make older people sicker, even if they have been fully vaccinated. Prior to delta, vaccination was known to impact factors that likely influence transmission. Not only did vaccinated people tend to have lower viral loads, but they also had milder symptoms and were sick for less time.
“The virus itself, as it starts, is a dangerous virus. It’s a highly transmissible virus. The delta variant is even so,” Van Kerkhove said. “It’s doubly more transmissible than the ancestral strains. They become more fit the more that they circulate and so the virus likely become more transmissible because this is what viruses do, they evolve, they change over time.” She highlighted that it’s imperative that nations follow public health measures, like social distancing and wearing masks, while nations distribute more vaccines around the world, especially in those with the lowest rates of immunization.
Dr Bruce Aylward, senior advisor to the director-general at WHO, said we need about 70% coverage globally, to really slow down the transmission and reduce the risk of emergence of new variants. Meanwhile, Dr Rochelle Walensky, director of the US Centres for Disease Control and Prevention, in a statement said high viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with delta can transmit the virus.
Researchers found evidence that viral loads were similar among 127 fully vaccinated people and 84 others who were unvaccinated, partially vaccinated or whose vaccination status was unknown. Viral load is proxy for how likely someone might be to transmit the virus to others.