The Health Secretary said that that the Scottish Government is working to understand the cause of the recent spike in infections in the south side of the city.
Mr Yousaf said that case numbers are rising in areas with a “large diverse community”, with fears that the April 02 variant is the reason for the surge.
Public health officials suspect that the strain, which has previously been referred to as the so-called Indian variant, may have been imported from abroad.
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Speaking on BBC Radio 4’s Today show, he said: “In a few concentrated hotspots…we are seeing significant community transmission.
“The levels and the numbers of cases are continuing to rise.”
Mr Yousaf added: “What we are seeing is it’s coming in areas where there is a large, diverse community so therefore there is a probability the variant has come in from international travel.
“Therefore we are trying to get to the bottom of how it managed to get in.”
Yesterday it was announced that Glasgow will remain in level three lockdown, as experts remain unconvinced that the recent outbreak is on its way out of the city.
Testing has been ramped up across the south of Glasgow over the past two weeks, with a number of drop in vaccination clinics also popping up.
Nicola Sturgeon said that the measures taken so far have helped to stabilise the number of infections.
There is hope that Glasgow could move down to level two from next Saturday if the rise in cases does not result in hospitals becoming overwhelmed.
A decision is expected to be made by Wednesday next week.
Speaking at a press conference, the First Minister said: “The view of the national incident management team is two-fold. Firstly, that it would be premature to move Glasgow out of Level 3 immediately this week while the situation remains so fragile.
“However, and secondly, if incidence continues to stabilise and assuming levels of hospitalisation remain reasonably stable, the incident management team has made clear to me that they would support a move to Level 2 from the end of next week.
“My message to the people of Glasgow is don’t lose heart.
“On the contrary, take heart from the progress that we are seeing.
“I live in Glasgow so I know how hard this is from my own personal life, but please continue to help with all of the public health efforts that are in place because if we continue to do this then we will make that move down from Level 3 to Level 2, and then after that hopefully get back on track and down the levels further.”
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