Reduced Exposure = Reduced Risk

It’s easy to think about exposure to the Coronavirus in terms of absolutes: Either I get the virus, or I don’t. But it’s not that simple. The amount of the virus you are exposed to, is influential in both determining whether or not you get sick, and  how severe the illness is likely to be. 

The amount of virus a person is exposed to is referred to as viral inoculum. In this video, Dr. Monica Gandhi, a UCSF Professor of Medicine, explains that wearing masks reduces the viral inoculum and can double the number of asymptomatic cases when a group of people have been exposed to the virus. 

Dr. Monica Gandhi Viral Inoculum Video


Here’s a quick summary of six key takeaways from Dr. Gandhi’s presentation. 

1. When people don’t wear masks and get infected with the Coronavirus, scientific studies show that  approximately 40 - 45 percent of the cases are asymptomatic. This is one of the most deadly parts of the coronavirus, because people who don’t show symptoms, still spread the virus. However, because a severe case of Covid-19 can lead to hospitalization, long-term health issues, and death, it’s obviously preferable to have an asymptomatic or mild case.

2. Face masks are important not just in preventing the transmission of the Coronavirus, but also because wearing a fabric face mask can limit the amount of coronavirus that makes it into the immune system, leading to a mild or asymptomatic case of COVID-19, the disease caused by the virus.

3. It wouldn’t be ethical to conduct a study where we knowingly expose people who do and don’t wear masks to the virus, but cruise ships have unwittingly shown us what happens. One of the earliest outbreaks was on the Diamond Princess where nobody wore masks. Of those infected, 18 percent were asymptomatic and 82 percent developed symptoms.

Subsequently an Argentinian cruise ship had an outbreak and gave masks to all passengers and crew. 128 out of 217 passengers later tested positive, but 81 percent were asymptomatic because masks reduced the amount of virus people were exposed to.

4. Another good example of the efficacy of masks can be seen in two outbreaks of the virus at an Oregon seafood processing plant and a Tyson chicken processing plant. In both settings, workers wore masks, and 95 percent of all cases were asymptomatic.

5. In East Asian countries where people are accustomed to  wearing masks such as Hong Kong, Taiwan, Thailand, South Korea, Singapore and Vietnam, the number of cases has been relatively low and the mortality rate is exceptionally low.

6. While asymptomatic infections are bad because people can unwittingly spread the disease, they may result in cellular level immunity to the virus.

According to Dr. Gandhi and top CDC officials, widespread mask wearing could stop the pandemic in 4-8 weeks. To learn more, watch Dr. Gandhi’s presentation