The UK coronavirus variant, more infectious than the previously dominant strain, has taken over as the main cause of new COVID-19 cases in Slovakia, Prime Minister Igor Matovic said on Friday.
The central European country of 5.5 million has struggled to bring down daily cases despite lockdown measures and widespread testing, which is required for people to go out including to work.
Hospitals have been strained, with 3,560 coronavirus patients on Thursday.
Matovic told a news conference the government had checked all positive samples of PCR laboratory tests taken in the country on Wednesday and results showed 74% were the UK variant, a touch above the 71% in partial findings he had reported earlier on Friday.
The British variant is believed to be up to 70% more infectious than the previously dominant strain, and may also be 30% more lethal, scientists say.
"We are in a very tough situation... There is no country in Europe with a higher documented proportion of the British mutation," Matovic said.
The proportion was even higher among coronavirus patients at the Louis Pasteur University Hospital in the eastern Slovak city of Kosice where tests showed 91% carried the UK variant of the virus, news agency TASR reported.
Matovic said that despite the findings, Slovakia would go ahead with the launch of a tiered system of measures from Monday which allows some schools to open even in the current highest level of restrictions.
Health Minister Marek Krajci said kindergartens and lower grades of elementary schools and final grades of secondary schools would be allowed to reopen.
Local authorities will make a final decision depending on conditions in their regions.
People will still be required to undergo tests, at regular 1-3 week intervals depending on local epidemiological situation, to be allowed to commute to work and move around the country.
Slovakia has recorded 5,050 deaths from the coronavirus.
(Reporting by Jan Lopatka; Editing by Mark Heinrich, Kirsten Donovan)
