BT Group PLC (LON:BT.A) chief executive Philip Jansen has tested positive for coronavirus and has gone into self-isolation.
Jansen said he met several other people in the telecoms industry over the past week and has alerted them to his Covid-19 diagnosis.
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Under advice from Public Health England, BT is conducting a deep clean of its head office and giving advice to any employees who have had contact with the boss.
"Having felt slightly unwell I decided as a precaution to be tested. As soon as the test results were known I isolated myself at home," Jansen said.
He added: "Given my symptoms seem relatively mild, I will continue to lead BT but work with my team remotely over the coming week. There will be no disruption to the business."
As of Thursday, 12 March, there have been 590 confirmed cases of coronavirus in the UK out of 29,764 people tested, and eight people who tested positive have died.
Worries about the spread of the virus and the economic effects saw the FTSE 100 crash 11% on Thursday, the worst day since October 1987, with Wall Street indices down almost 10%,
Traders are eying a positive start for the FTSE 100 on Friday, however.