Night sweats could be causing a new symptom among patients with Omicron's sub-variant BA.5, according to a leading UK immunologist.

Luke O'Neill, Professor of biochemistry at Trinity College in Ireland, warned that people with the BA.5 variant may find it difficult to sleep due to night sweats, The Sun reported. The NHS classifies night sweats as those which can sodden the night clothes and bedding.

"One extra symptom from BA.5 I saw this morning is night sweats," O'Neill was quoted as saying to Newstalk - an Irish radio station. Calling the symptom "another curveball", the immunologist said that it is a result of BA.5 colliding with immune systems resulting in a "different disease".

"The disease is slightly different because the virus has changed," O'Neill said. "There is some immunity to it obviously with the T-cells and so on -- and that mix of your immune system and the virus being slightly different might give rise to a slightly different disease, strangely enough, night sweats being a feature.

"But very importantly, 'if you are vaccinated and you're boosted, it doesn't progress into a severe disease' is the message to keep reminding people." Intense night sweats have also been linked to previous Omicron sub-variants.

According to Mayo Clinic, night sweats are "repeated episodes of extreme perspiration that may soak your night clothes or bedding and are related to an underlying medical condition or illness". Previously, night sweats have typically been connected with other diseases such as the flu, worry, or even cancer.