COVID symptoms kick in just two days after infection, a world-first study has revealed.
Until now, the World Health Organization has said it takes five to six days, on average, for the effects of Covid to kick in, based on research.
The first results of a human challenge study – in which people were deliberately infected with the virus – show otherwise.
Researchers at Imperial College London deliberately infected 36 people with coronavirus.
They found symptoms and spreading start days earlier than previously believed, at just 42 hours.
People’s virus levels peak after five days but linger for as long as 12 days.
Dr Andrew Catchpole, chief scientific officer at trials firm hVivo, said: “This shows the potential of the virus to replicate very, very quickly.”
Professor Christopher Chiu, from Imperial College, added: “Even if people had no symptoms at all, they all generated extremely large amounts of virus which really explains how the pandemic spread so rapidly.”
Only half the group, who were all under 30 and were unvaccinated, became infected.
They were exposed to the virus with the equivalent of less than one respiratory droplet if somebody was at the peak of their infection.
Symptoms to watch for
The symptoms experienced by those who became unwell included a stuffy or runny nose, sneezing and sore throat.
Some of the group experienced headaches, muscle/joint aches, tiredness and fever.
It suggests that even with the original strain of the coronavirus, which the study used, symptoms are typically mild and cold-like.
The first signs you are infected, such as a runny nose, could be mistaken for something else.
A loss of taste or smell was not reported by study participants until around a week after respiratory symptoms.
While the study was conducted with the Wuhan Covid strain, experts believe the findings would also apply to the Delta and Omicron variants.
Data show that the most common symptoms of the virus in the UK now, as Omicron dominates, are:
- Runny nose
- Headache
- Fatigue
- Sore throat
- Sneezing
- Persistent cough
- Hoarse voice
The data is from the ZOE COVID Symptom Study app.
Reinfections on the up
It comes as an Office for National Statistics report revealed that people who get infected for a second time end up with more virus in their body than the first time.
Despite a higher viral load, people are no more likely to get symptoms and death rates for Omicron are still much lower.
Reinfections now make up around 10 per cent of all cases, with an average of 8,600 per day in England.
Monday (January 31) was the first day that reinfections were included in the daily Covid case tally.
Before, the daily figures included only people who had tested positive for the virus for the first time.
The UK Health and Security Agency said: “As the pandemic continues and more variants emerge, it is more likely that people will be reinfected with Covid-19.”
Of the 14.8 million infection episodes in England since the start of the pandemic, some 588,114 (four per cent) are likely reinfections.
Another 88,085 cases were confirmed yesterday, a 14 per cent fall compared to last Wednesday.
There were 534 deaths – although this included a large backlog of numbers – and hospital patient numbers fell again.
Mass testing from the ONS found infections levelled off across the UK last week at 2.9 million.
