What is the difference between people who are asymptomatic and pre-symptomatic?

Asymptomatic and pre-symptomatic both refer to people who do not have Covid-19 symptoms.

According to the World Health Organisation (WHO), the difference is that asymptomatic refers to people who are infected but never develop any symptoms.

Pre-symptomatic people may not have symptoms at present but go on to develop them later.

The US Centers for Disease Control and Prevention (CDC) warns that pre-symptomatic Covid-19 carriers are the most contagious, as the virus can spread at least 48 hours before symptoms develop, which usually appear two to 14 days after exposure.

Without knowledge, a pre-symptomatic person can infect others while still feeling healthy. Others might have symptoms that are so mild that they might not notice them.

“Children infected with the virus that causes Covid-19 are more likely than adults to be asymptomatic or to have only mild symptoms,” said the CDC.

“The exact percentage of children infected with the virus that causes Covid-19 who are asymptomatic is still unknown, but recent large studies have suggested that about 16% of infected children do not develop symptoms.”

The centre also makes an example of asymptomatic and pre-symptomatic pupils in schools, saying they could potentially pass it to others.

“Even if schools attempt to screen for all known Covid-19 symptoms, asymptomatic and pre-symptomatic pupils with the virus will not be identified and could potentially pass it to others,” said the CDC.