The time you need to isolate after contact with a confirmed coronavirus case could be reduced to seven days, according to a new study.
Latest research suggests that the risk of passing it on does not increase after a week. This is good news for those who contract the disease and then need to stay away from their loved ones.
The study takes into account the potential viral load of infected people as well as the sensitivity of Covid-19 tests. It is estimated that those who test negative after seven days of quarantine are unlikely to be infectious.
The researchers believe these people could potentially be released without increasing the risk of virus retransmission beyond what is expected from someone who isolates for 14 days without doing a test.
The modeling also estimates that using daily rapid lateral flow antigen (LFA) tests on tracked contacts for five days could potentially replace the self-isolation requirement if all tests are negative.
This could potentially prevent a similar level (50%) of virus retransmission as the 14-day approach without the need for quarantine when people isolate upon receiving a positive test, the study said.
However, the study does not assess the number or cost of tests that would be required for this approach.
The authors stress that people should continue to follow official guidelines on quarantine and self-isolation, which the UK government has set at 10 days until their results can be verified through further investigation.
They add that this approach could improve compliance and reduce the financial and social impact on those affected, while keeping control of the virus at least as good, if not better, than the recommended 14-day strategy.
Deputy Professor Sam Clifford, co-lead author and member of the CMMID Covid-19 Working Group at the London School of Hygiene and Tropical Medicine, said, “Adhering to quarantine rules is key to reducing the spread of Covid-19.
“Our results suggest that including contact testing in a trace isolate system may help reduce quarantine times. This, in turn, can improve compliance by making it easier to complete the entire isolation period.
“However, our study did not assess the cost and further studies are needed to address this and further verify our results.
“An integral part of the impact of any strategy we modeled was strict isolation in the event of Covid symptoms, which should be followed at any time after exposure, including after the end of the specified quarantine period or after negative test results.”
Assistant Professor Elizabeth Fearon, a member of the CMMID Covid-19 Working Group at the London School of Hygiene and Tropical Medicine, added, “Tests alone have no impact on transmission unless cases are funded and socially supported to support themselves . isolate after a positive test. “
Around 95% of people who develop coronavirus symptoms show signs of illness within 14 days of exposure to the virus.
In the new study, published in The Lancet Public Health, researchers used mathematical models to estimate the effect of various quarantine and testing strategies on reducing the transmission of pursued secondary infections.
Using data from Public Health England (PHE) and NHS England, they simulated the level of virus an infected person would likely produce at each stage of the infection, as well as the time of symptom onset, test sensitivity, and time tracking and testing time.
The model assumes that self-isolation adherence is moderate, with 67% of people completing the recommended 14-day period after testing positive and 50% of confirmed case contacts completing 14 days.
Based on the assumptions, it is estimated that completing the 14-day contact period for Covid-19 cases will prevent 59% of virus transmission.
A similar proportion of onward transmission could possibly be prevented with just seven days of self-isolation if a PCR or LFA test is performed on the last day (PCR – 54%, LFA – 50%).
The authors believe that reducing delays, such as tracing and notifying contacts, is a key factor in ensuring quarantine.
The researchers note that the model is based on the assumption that the LFA test operates at a higher sensitivity, capturing an average of 76.8% of cases that test positive in a PCR test.
Analysis of the LFA test for the lower number from the Liverpool trial, 48.89%, gave comparable but slightly lower results.
In this analysis, an LFA test on the seventh day of self-isolation would prevent 44% of virus transmission, while a daily LFA test for five days would prevent 43% of transmission, according to the study.
The authors say their study ignored other aspects of the test and trace system that could affect virus transmission.
This includes the number of people with Covid-19 who are completely unaware of the system, the variation in the number of secondary cases generated by each infected person, and the proportion of secondary cases that are missed by tracers.