The Centre for Covid-19 Situation Administration (CCSA) is looking to upgrade the ventilation systems at Pathum Thani markets following the high infection rates at these locations.
Cases at three markets in Pathum Thani have spread to nine other provinces with the latest number of infections standing at 355, according to the CCSA.
Apisamai Srirangson, assistant spokesperson at the CCSA, said authorities investigated and contained infections traced back to Pornpat market in Pathum Thani.
Patients who contracted Covid-19 at the market reportedly spread the virus to people in Nakhon Nayok, Bangkok, Phetchaburi, Samut Prakan, Saraburi, Ayutthaya, Nakhon Ratchasima, Ang Thong and Nonthaburi.
No related infections were reported in Chaiyaphum and Nakhon Pathom, where infected persons from Pornpat market had visited, according to Dr Apisamai.
The Department of Disease Control had reached out to the two provinces and was closely monitoring the situation there, she said.
No new cases have been reported so far, she said.
A total of 5,743 people had been tested at the Pornpat, Suchart and Rangsit markets and the surrounding communities, 355 of whom had tested positive for Covid-19 but most were asymptomatic, Dr Apisamai said.
A total of 7,417 people have been tested at the markets and other at-risk places in the province. The CCSA aims to test at least 10,000 people there.
"The main reason why infections occurred at a high rate at the markets was bad ventilation that made it easy for the virus to spread," Dr Apisamai said.
"The airflow rates measured at the markets were zero."
Most of those infected were people who spent relatively short periods in the market, she said.
These patients are primarily vendors and their employees who usually worked long hours and traded extensively in other provinces, she added.
The Department of Health would propose measures to improve the standards of markets in the short term for the Covid-19 pandemic and the long term for future outbreaks.
The Public Health Ministry would provide ventilators and require markets to adjust their structure.
Market cleanliness would also be heightened and the stalls would be placed further apart, said Dr Apisamai.
Market vendors would have to register with municipal authorities for health checkups to minimise the risks of spreading diseases to customers.
