Doctors and health officials have warned that the rising number of Covid-19 infections poses a significant threat to the UK’s ability to run trains, buses, hospitals and other key services.
More and more people face going into quarantine and that could have grave consequences, they say. As a result, isolation times for those testing positive for Sars-CoV-2 have been cut from 10 to seven days to reduce the pressure on industry.
But is this reduction justified? Or is there room for even further quarantine cuts to be made, as has been done in the US? These are critical questions, the answers to which could determine how quickly the nation emerges from the wave of Covid-19 cases it is now experiencing.
In England and Northern Ireland, if you’ve tested positive or have symptoms, you can now stop self-isolating after seven days, instead of 10, if you get two negative lateral flow test results on days six and seven. In Scotland and Wales, the 10-day limit is still in force.
“We know that people who get Covid-19 are most infectious early on around symptom onset, and that the risk of transmission declines pretty quickly after that,” says epidemiologist Billy Quilty, of the London School of Hygiene and Tropical Medicine.
“By the time someone finds out that they are infected by developing symptoms or testing positive, it’s already been two or three days since they were exposed, and they may have already been infectious for a day or two. So after five days of isolation, they’re really on day seven or eight of their infection. As a result, we estimate that there is a low risk associated with isolation periods of five days or more.”
Scientists say Omicron may infect people more quickly, but possibly for a shorter period than previous variants. “However, we need to find out if that is the case as soon as possible,” said Quilty. “We also need to make sure that people are not isolating for an unnecessarily long time, especially if this becomes a very acute staffing crisis.”
The need for further research is also backed by epidemiologist Prof Dame Anne Johnson, of University College London.
“There is a large variability in how infectious people are and how much virus they shed. So we need more studies to understand when it’s reasonable for people to be released from quarantine – though we need to face the fact that we cannot eliminate all risk.”
Johnson added that she wanted to see more data on the distribution of viral loads in different people according to their symptoms and at different times of their infection. “We need to better understand how infectious individuals are likely to be at different times and to know when infectivity drops off,” she said.
Most scientists are now more optimistic about the likely impact of Omicron, though they worry about the short-term effect it might have on hospitalisations. “In a population that was previously unexposed to a virus, it takes time – through natural infections and vaccines – to get to the situation where you have gradually built up immunity in the population to the extent that people will be getting infected without much impact,” said Johnson.
“That is the general direction we are travelling in – as long as we don’t get a new variant that is so different it causes a lot of disease.”