The US has decided to cut the recommended self-isolation time with Covid to five days. How long are people with Covid infectious?
There are rules for self-isolation in the UK.
If you have a negative test for Covid on days six and seven, you can cut your self-isolation from 10 days to seven.
If a person has tested positive for a vaccine, they don't need to self-isolate, but those who aren't have to.
The self-isolation period for those who test positive in Scotland, Wales and Northern Ireland is 10 days.
Someone with Covid is infectious for a long time.
It has been known for a while that people can be infectious from about two days before symptoms appear.
According to Harvard Medical School, most people will no longer be contagious if their symptoms have not improved by the 10th day.
The immune response to the Omicron variant would be the same as it was in previous versions, according to Dr Tang, a professor of respiratory sciences.
Prof Lawrence Young said that it was likely that the infectious period was shorter with the Omicron variant, and that it was also likely that the vaccine status was a factor. The infectious period can last between two to three days after you become sick.
The UK Health Security Agency says the new approach for England reflects the latest evidence on how long cases transmit the virus for, and supports essential public services and supply chains over the winter.
Dr Richard Tedder said the shift was a compromise and was based on the assumption that people with two negative tests are unlikely to transmit coronaviruses to contacts.
He said that it was probably correct, but that it might not hold if the future variant is not picked up by the flow tests.
Young agreed. The approach adopted in the UK is based on seven days and two negative flow tests. These tests can help determine if you are infectious.
How do the UK's rules compare to those of other countries?
In France and Germany, people with Covid have to self-isolate for 10 days if a test comes back positive.
The Centers for Disease Control and Prevention in the US has recently cut the recommended self-isolation period to five days if the person has no symptoms.
The CDC said the change was motivated by science that shows most transmission occurs in the one to two days before symptoms start. People who test positive should be isolated for five days if they are positive and then leave isolation if they can continue to mask their symptoms.
Those who have had their booster jabs or have recently completed the primary course of Covid vaccines do not need to self-isolate but should wear a mask around others for 10 days.
The World Health Organization proposed a 10-day isolation cut-off last summer. He said that they are taking into account the viral load drop-off after the first five days. He said that it would depend on how conscientiously masks were worn to limit further transmission as the viral load drops.
Tang said that it was just another compromise as we learn to accept and live with the virus. Different countries will approach this differently because of their local knowledge, studies, experience, and competing resources and priorities.
There is no requirement for a negative Covid test before ending self-isolation in the US.
Some people stay infectious for 12 days. He said that the new guidance from the CDC to not have a negative test is reckless. I don't want to sit next to someone who turned Positive 5 days ago and hasn't tested.