Three weeks ago, when knowledge of the coronavirus was still in its infancy, a middle-aged man from Hove, East Sussex, travelled to Singapore for a sales conference.

The event, organised by his firm, Servomex, was a chance to sharpen up sales skills and network with colleagues from other countries in the plush surrounds of the five-star Grand Hyatt hotel, where rooms can cost £1,000 a night.

The trip exposed the Sussex businessman to the Wuhan coronavirus and in the days after the conference it is believed he passed the bug to at least 11 Britons in three countries, prompting concerns about the danger posed by so-called super-spreaders.

The unnamed man, the first Briton to have tested positive for coronavirus, attended the sales conference from 20 to 22 January. He was among 94 delegates – out of a total of 109 – who travelled from abroad. The foreign delegates included one from Wuhan, the Chinese city at the centre of the outbreak.

After the conference, the Briton travelled to the French ski resort of Les Contamines-Montjoie near Mont Blanc, where he stayed with his family between 24 and 28 January. He flew back to the UK on a busy easyJet flight from Geneva to Gatwick. Still oblivious to the fact he had the virus, which has a two-week incubation period, he returned home and on the evening of 1 February he visited a local pub, The Grenadier, in Hove.

It was only after being informed by the conference organisers that another delegate had contracted the virus that he alerted the public health authorities and subsequently tested positive.

As protocol dictates, a scramble began to identify all those with whom he had been in contact to ascertain whether they too had been infected. Five workers at The Grenadier were instructed to self-isolate. The man’s travels in the intervening period multiplied the number of people he had potentially infected, and cases linked to him began to emerge.

On Saturday, the French health minister, Agnès Buzyn, said five British citizens, including a nine-year-old child, had tested positive for the coronavirus. They had stayed in a chalet in Les Contamines-Montjoie, which had been visited by the businessman from Hove. Buzyn said another six UK nationals were being kept under observation in French hospitals, and two schools the nine-year-old visited were being shut as a precaution.

On Sunday, more cases linked to the businessman emerged. Public Health England (PHE) said another patient in the UK had tested positive after the virus was passed on in France from another already confirmed UK case. It was announced that a British man living in Mallorca, who had been in Les Contamines-Montjoie with his family until 29 January, had also tested positive.

On Monday, it was confirmed that a further four people in the UK – three men and a woman in Brighton – had tested positive for coronavirus. The chief medical officer, Prof Chris Whitty, said all were “known contacts of a previously confirmed UK case, and the virus was passed on in France”.

Dr Andrew Freedman, a reader in infectious diseases at Cardiff University, said: “This is not particularly surprising but it does appear that the index case has passed on the infection to an unusually large number of contacts. As such, he could be termed a super-spreader.”

The Hove businessman is in an isolation unit at St Thomas’s hospital in London, having been transferred from Brighton on Thursday. The effort to identify and – where necessary – isolate and test people who may have been in contact with him continues. Those potentially at risk include passengers who sat near him on flight EZS8481 from Geneva to Gatwick on 28 January.

Dr Nick Phin, a deputy director of the National Infection Service at PHE, said: “Our priority is speaking to those people who have had close and sustained contact with confirmed cases so that we can advise them on what they can do to limit the spread of the virus.”