• U.K. Covid-19 cases rose for the first time in two months in the week to June 2, according to new estimates from the Office of National Statistics.
• A total of 989,800 people tested positive for the virus in the week — up from 953,900 a week earlier — the ONS said Friday.
• It comes at a time when Health Secretary Sajid Javid has dubbed the country "properly post-pandemic."

U.K. Covid-19 cases have risen for the first time in two months, according to new data, which warns of a possible further spike ahead.

A total of 989,800 people tested positive for the virus in the week from May 27 to June 2 — up from 953,900 a week earlier — estimates from the U.K.'s Office for National Statistics (ONS) showed Friday.

That figure equates to around 1.5% of the population, or one in 65 people.

It comes at a time when Health Secretary Sajid Javid has dubbed the country "properly post-pandemic."

Javid on Saturday told The Times newspaper that Covid-19 was "no longer a pandemic," describing it as "endemic" like the flu and other viruses. "We should be proud as a country of how we tackled it," he added.

The uptick recorded by the ONS was likely driven by the original omicron variant BA.1 and the newer variants BA.4 and BA.5.

While all four countries in the U.K. recorded an increase in cases, the ONS said the overall trends in Scotland and Wales were "uncertain." As of June 2, England had 797,500 cases; Northern Ireland had 27,700; Wales had 40,500; and Scotland had 124,100.

The data, which are based on confirmed positive Covid-19 test results of those living in private households, give an early projection of the course the virus may take in the coming weeks.

It is compiled by testing thousands of people from U.K. households at random, whether or not they have symptoms, and is thought to provide the clearest picture of Covid-19 infections in Britain since free public testing was abandoned in England and Scotland.

A new wave ahead?

Some health researchers and physicians have warned that the uptick suggests a new wave of infections is coming.

"A new wave is now starting," Christina Pagel, director of University College London's Clinical Operational Research Unit and a member of the scientific advisory group Independent Sage, said during a virtual press conference Friday.

"Given where we are now, I expect that to go up again next week," she added.

The data released Friday predates the U.K.'s Platinum Jubilee bank holiday, a four-day weekend of celebrations and social gatherings to commemorate Queen Elizabeth II's 70 years on the throne.

The U.K.'s Health Security Agency said that could mean data for the following week is somewhat delayed or distorted.

"Recent data has shown a small rise in positivity rates and in hospitalizations with Covid-19. These small increases should be interpreted with caution as data may be subject to delays due to the Jubilee bank holiday," Dr. Jamie Lopez Bernal, consultant epidemiologist for immunization and countermeasures at the UKHSA, said Thursday.

'Never a good combination'

According to the latest ONS data, positive cases increased among people aged 35 to 49, with early signs of increases among 16 to 24-year-olds. Cases dropped in those aged 50 to 69 and over 70.

Simon Clarke, associate professor in cellular microbiology at the University of Reading, told CNBC Monday that the recent spike was "inevitable" as regular social interactions resume and vaccine immunity wanes over time.

Omicron BA.1 is the initial variant of omicron that caused infections to surge across the U.K. in December and early January this year. Newer variants BA.4 and BA.5, meanwhile, were designated as "variants of concern" by the UKHSA in May, and initial research suggests they have a degree of "immune escape," making it harder for the immune system to recognize and fight the virus.

Professor Rowland Kao, chair of veterinary epidemiology and data science at the University of Edinburgh, noted that the lack of Covid testing combined with an increase in positive cases did not provide a positive outlook.

"The number of people taking tests is going down and the positivity is going up, and that is never a good combination," he said.

However, he added that the most serious effects of another outbreak may not be felt until the winter months.

"Short-term it may be OK," he said, citing concern for vulnerable groups. "But it's really looking four, five months ahead [that's concerning]."