Most Covid-19 infections are spread by people who have no symptoms, the CDC says in newly updated guidance.
Most coronavirus infections are spread by people who have no symptoms, the US Centers for Disease Control and Prevention said in newly updated guidance.
“Most SARS-CoV-2 infections are spread by people without symptoms,” the agency said in a section of its website devoted to explaining the science of how to use masks to control the spread of the virus.
“CDC and others estimate that more than 50% of all infections are transmitted from people who are not exhibiting symptoms,” it added in the guidance posted Friday.
According to the CDC, 24% of people who transmit the virus to others never develop symptoms and another 35% were pre-symptomatic.
It also said 41% infected others while experiencing symptoms.
Peak infectiousness comes five days after infection, the agency said on the website.
Previously, the health organization has not characterized what percentage of infections are spread by symptomless people.
“Infection is spread primarily through exposure to respiratory droplets exhaled by infected people when they breathe, talk, cough, sneeze, or sing,” the agency added.
The CDC said studies have shown 40-45% of infected people never develop symptoms.
“Among people who do develop symptomatic illness, transmission risk peaks in the days just before symptom onset (presymptomatic infection) and for a few days thereafter. “
So, people are spreading the virus when they have no idea they are infected.
The CDC also now said masks can help prevent people from inhaling the droplets, large and small, that carry the virus.