The number of Covid-19 infections at Chulalongkorn University has risen to 22, with 13 of them being security guards.
Officials have since taken samples from 20 suspected locations in the university and found traces of the virus at face and finger scanners used by security guards to check in for duty.
Taweesilp Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration, said the cluster, especially the virus traces found on finger scanners, emphasised the need for frequent hand washing.
"The security guards shared the same workplace, training grounds and finger scanners where the disease was found, and also had meals together," Dr Taweesilp said about the cluster whose first case was detected on Jan 29.
"This group of people also transmitted the disease to five relatives."
In other Covid developments yesterday, Chiang Mai began imposing travel restrictions on people arriving from Pathum Thani and from the Mae Sot border district of Tak.
From now on those visitors must register with Chiang Mai's Covid-19 tracking system "CM-CHANA", download and install the government's Mor Chana location-tracking app on their mobile phones, report on arrival to local disease-control authorities, and either do 14-day home quarantine or get tested for Covid-19, said provincial governor Charoen Sanguansat.
Pathum Thani had previously recorded 48 new Covid-19 infections, prompting two fresh markets to be shut from last Friday until Feb 25, during which both Pornpat and Suchart markets are being fully disinfected.
The closure also covers commercial buildings near the two markets, on the Rangsit-Pathum Thani 17 road and on Rangsit-Nakhon Nayok 19, 21, 23, 25 and 27 roads, said Pathum Thani governor Chaiwat Chuenkosum.
Pol Lt Gen Sophon Phisutthiwong, deputy Bangkok governor and director of the capital's Covid-19 situation administration centre, has ordered five districts of Bangkok bordering Pathum Thani -- Don Muang, Sai Mai, Bang Khen and Klong Sam Wa and Lak Si -- to step up Covid-19 prevention measures.
It follows news that a medical student at Thammasat University, Pathum Thani, last Saturday contracted Covid-19 from a patient at Thammasat University Hospital.
The student was one of seven people who came into contact with the patient and had been tracked down, said Assoc Prof Dr Dilok Piyayotai, dean of the university's Faculty of Medicine.
He added that 47 people in total had come into contact with the infected patient, of whom 42 people had been cleared of infection and the other five were still awaiting their results.
The government recorded 72 new Covid-19 cases yesterday, raising the accumulated total to 24,786 since the start of the pandemic.
No new deaths were reported, leaving the toll at 82.
