Anyone who has been identified as a close contact to any of the people with Covid-19 on Barra is being offered a test, as efforts to clamp down on the spread intensify.
A total of 10 positive cases have been identified this month, with the virus reaching the island for the first time in recent weeks.
NHS Western Isles said the number of people self isolating after being identified as close contacts by Test and Protect was 80 a few days ago, but this is believed to have increased.
Tests are being offered to help the health board to identify positive cases as early as possible.
A spokeswoman said: “Those who are identified as a close contact of someone who has tested positive for Covid-19 must self isolate for 10 days from the date of their last contact with the positive individual, in line with what is explained to them by the NHS Western Isles Test and Protect Team.
“We cannot stress strongly enough that, even if close contacts test negative for Covid-19 as part of this process, this does not change the requirement to complete their self-isolation period.
“Even if a close contact’s test is negative, there is still the possibility that they are incubating the virus and could inadvertently pass it on to others.
“We would remind individuals that, if they are told to self-isolate by NHS Test and Protect, the period of self isolation starts immediately.”
To book a test, people should contact 01851 601151 or email: email@example.com