Covid cases are still rising across the UK, with infection levels now at the highest estimate since late April.
A total of 2.7 million people in the UK are estimated to have had the virus in the week up to 1 July, new figures from the Office for National Statistics (ONS) show, which is up 18% from 2.3 million the previous week.
Infections are still below the record high of 4.9 million, which was reached at the end of March during the BA.2 Omicron wave, but two newer Covid variants are continuing to drive cases.
Together, the BA.4 and BA.5 variants now make up more than half of new cases in England and have become dominant in the UK.
They have been classified as “variants of concern” by the UK Health Security Agency (UKHSA) and analysis has found that both strains were likely to have a “growth advantage” over BA.2.
They also have a degree of “immune escape”, meaning the immune system can no longer recognise or fight a virus.
There is “currently no evidence” that BA.4 and BA.5 lead to more serious disease than previous variants, but they can cause slightly different symptoms - including one that appears during the night.
What symptoms can BA.4 and BA.5 cause?
Covid symptoms have become a lot more varied since the virus broke out more than two years ago, making infection harder to spot.
The ZOE Covid Study app, launched in March 2020, has helped to keep track of common symptoms as users regularly report on their health, with researchers identifying a runny nose, headache, a sore throat, persistent cough and fatigue as the most common signs.
However, it appears that a new, more unusual symptom of the BA.5 variant is emerging.
Professor Luke O’Neill, a Trinity College immunologist, has said the now dominant variant in Ireland can cause a slightly different symptom than its predecessors and will affect people during the night.
Speaking on The Pat Kenny Show, Prof O’Neill said some people infected with BA.5 have reported suffering from night sweats.
Night sweats are when you sweat so much that your night clothes and bedding are left soaking wet, even though where you are sleeping is cool.
He told the show: “Most cases in Ireland at the moment would be BA.5, for instance, same in the US.
"It’s another curveball that has been thrown at us by this virus, and BA.5 is the dominant variant that’s out there at the moment.
"One extra symptom for BA.5 I saw this morning is night sweats. The disease is slightly different because the virus has changed.
"There is some immunity to it, 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 - with strangely enough - night sweats being a feature.
"But very importantly if you’re vaccinated and you’re boosted, it doesn’t progress into severe disease".
Members of the public have been advised to “go about their normal lives” but in a “precautionary way”, with health experts highlighting handwashing, keeping distance where possible and wearing a face covering in enclosed, poorly ventilated places as measures to help reduce the risk of spreading infection.
People are also urged to stay at home and avoid contact with others if they experience any Covid symptoms or feel unwell.
Will there be another vaccine rollout?
People aged 65 and over will be offered a booster vaccine, alongside frontline health and social care workers, this autumn, and there is a suggestion that everyone over the age of 50 could also be included in the programme.
Around one in six people aged 75 and over in England (16%) have not received any doses of Covid vaccine in the past six months, putting them more at risk of severe disease which could put increasing pressure on hospitals in the coming months.
Prof O’Neill said he believes new versions of the Covid vaccines will be available in time for winter and encouraged people who are yet to get vaccinated to come forward.
He said: “Both Pfizer and Moderna have said they’ll have an Omicron vaccine by September, and they’ll have a BA.4/5 by October.
"So when we get to that point, it would make sense to start using those newer ones. But... the current one is still giving good protection anyway.
"Like the flu, you’ll change the vaccine based on the variant that’s around at the time".
He added: "Remember the ones who are getting sickest are unvaccinated, or haven’t had the booster.
"Hence the message: get the booster because it will give you this added protection.”