A new study suggests that one in 10 people may still be infectious 10 days later, and some even after 68 days.
About one in ten people may have significant levels of the SARS-CoV-2 10 days after their original infection. In Australia, current guidelines place infected people in seven days of isolation.
The new study, led by the University of Exeter, in the UK, employed a newly adapted test to detect levels of the virus in 176 participants, confirmed to have been infected with SARS-CoV-2. The test is meant to only detect levels of live (and potentially infectious) virus.
Researchers found that 13% of participants still showed significant levels of SARS-CoV-2 after 10 days. In a few cases, the test detected significant levels of the live virus after 68 days.
According to lead author, Merlin Davies, of the University of Exeter Medical School, their findings could have important implications. “In some settings, such as people returning to care homes after illness, People continuing to be infectious after ten days could pose a serious public health risk. We may need to ensure people in those setting have a negative active virus test to ensure people are no longer infectious. We now want to conduct larger trials to investigate this further,” Mr Davies said.
However, according to Dr Zoë Hyde, Senior Research Officer at the University of Western Australia, these new findings don’t add a great deal to what we already know.
“As far as I can tell, they’re measuring something they believe to be a proxy for live virus, but then they acknowledge in the strengths and limitations section of the paper that envelope gene subgenomic RNAs can be present after viral replication has ceased,” Dr Hyde told Medical Forum.
“So I’m inclined to believe they weren’t detecting live virus in that study,” Dr Hyde added.
Regarding current quarantine protocols, Dr Hyde says that WA should stick with the current arrangements for close contacts. In WA, current guidelines say that people entering the state need to self-quarantine for 12-14 days and need to present a negative PCR test result before leaving isolation. But, in other Australian states, rules have been relaxed, and quarantine only usually lasts for about seven days.
“For the other states and territories, I understand the rationale for shortening the quarantine period given the need to maintain essential services and supply chains, but I think there should be a requirement to test negative before leaving quarantine,” Dr Hyde said.
“I think there should be a requirement to test negative before leaving quarantine. Without this, some infections will inevitably slip through and go on to create new chains of transmission where people will have to isolate,” Dr Hyde added.