LONDON — Britain’s health department declared the new coronavirus an “imminent threat” to public health and announced a series of measures to combat the spread of the virus, a sign of the seriousness with which local health authorities are treating the fears of the epidemic.

The newly introduced measures — which apply only in England — are among the first in Europe to allow the health authorities to keep individuals in quarantine if public health professionals believe they may be at risk of spreading the virus.

Four more people in Britain linked to a cluster of transmissions at a ski resort in France tested positive for the coronavirus, bringing the total number of cases in the country to eight, the health department announced Monday.

The coronavirus has sickened more than 40,500 people, mostly in China, and at least 910 people have died since the virus first emerged in Wuhan, a city of 11 million people in the central part of the country late last year. Since that time, the virus has also spread to at least 24 countries, triggering fears of a global pandemic.