Cybersecurity company Exabeam says that two employees who attended the RSA Conference in San Francisco have tested positive with coronavirus.

One of the employees, a 45-year-old man with a heart condition, is very ill, Bloomberg reports.

RSA was one of the few big tech events go on as planned amid the spread of coronavirus, with the support of San Francisco Mayor London Breed. San Francisco would ultimately declare a state of emergency right around the time the conference began.

Other big events like the Game Developers Conference and Google Cloud Next, both slated to be held in San Francisco, have cancelled or otherwise postponed to a later date.

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Two attendees of the RSA cybersecurity conference – one of the few tech trade shows to go one amid coronavirus fears – have tested positive for the virus, according to the conference and their employer, Exabeam.

One of the two employees is reportedly very ill with the virus.

"We learned that two individuals who attended RSA Conference 2020 have recently tested positive for COVID-19," conference organizers said on its website Tuesday.

The California-based cybersecurity firm Exabeam tweeted Tuesday that "We recently learned and are saddened to share that two of our employees have tested positive for Coronavirus (COVID-19)."

When a Twitter user asked if the employees were at the company's booth at the 40,000-attendee trade show two weeks ago, the company responded "The two individuals who were at the conference may have been at our booth. If you visited our booth please be vigilant about monitoring yourself for symptoms and following guidelines to prevent possible infection."

Bloomberg reported Tuesday that an RSA attendee who appears to work for Exabeam "is seriously ill with respiratory issues." The news agency reported that the employee was a 45-year-old man from Connecticut with a heart condition.

Robert Siegel, an immunologist at Stanford University, said conferences are particularly conducive to spreading viruses. In fact, if you wanted to create the ideal system to spread something like the coronavirus, convening thousands of people from all over the world, packing them into a confined space where they shake hands and talk at close quarters, and then spitting them back out in different directions would be a good way to do it, he suggsted.

"In terms of spreading respiratory viruses, this is greatly facilitated by close contact between large groups of individuals, and by people arriving from and dispersing to distant locations," he said.

Mobile World Congress, South By Southwest and many smaller conferences before and since have cancelled at great cost because of the coronavirus crisis. The Game Developers Conference cancelled its San Francisco trade show as RSA wrapped up, despite encouragement from the city's tourism marketing agency.

RSA went on, even as sponsors pulled out

The RSA conference posted frequent reminders to attendees to wash their hands and avoid handshakes if they were uncomfortable. The conference also referred attendees to health guidance from the Centers For Disease Control and other agencies.

But it persisted in putting on the conference, even as sponsors IBM, AT&T, and Verizon pulled out as a cautionary measure.

San Francisco Mayor London Breed released a letter to RSA attendees the Friday before the conference that told them "San Francisco is open for business and events are proceeding as planned...We must set an example to prevent fear, rumors, and misinformation from guiding our actions." The letter noted that "the virus is not circulating in our community."

Five days later as the conference got under way, Breed declared a state of emergency in the city due to the virus. Breed and the department of health stressed that the emergency declaration was to help the city prepare in case the virus situation worsened.

The day of the declaration, Dr. Grant Colfax, San Francisco's director of health, said that "This is a global outbreak that is entering a new phase, and we must be prepared." He added, "This is not business as usual."

That same day RSA President Rohit Ghai opened the conference with a keynote in which he said "thanks to Mayor London Breed and her office for collaborating with our conference team to ensure a healthy and safe event for all."

San Francisco continued to encourage conferences after the declaration of emergency. "The City continues to encourage people to attend events and conferences," wrote Andy Lynch, a member of the mayor's staff, on February 28.

More than 118,000 people have been infected and over 4,200 have died of the virus. The US has reported 28 deaths.

San Francisco reported 14 total cases on Tuesday. On Monday the city banned non-essential group events held in city-owned facilities for two weeks.

RSA orgnizers declined to comment beyond the post on its website. Exabeam declined to comment beyond its tweets. The San Francisco Mayor's Office did not immediately respond to a request for comment.