World leaders and the World Health Organization have both questioned whether masks are an effective way to reduce viral transmission. A recent Sky News article discussed a study carried out in response to these statements that showed they do work. A team of researchers in Hong Kong investigated the rate at which COVID-19 was transmitted through airborne particles or respiratory droplets, and found that masks reduced the numbers by 75%.
The study involved two cages of hamster: one healthy cage, and the other infected with COVID-19. The team then placed a fan pushing air toward the infected animals, and found that without masks between the cages, two-thirds of the healthy hamsters were infected within a week. However, when they placed masks on the cage containing the infected hamsters, the infection rate dropped to around 15%. On top of that, the hamsters that became infected also had less of the virus in their bodies than the rodents who were infected without a mask.