Three close relatives of a Covid-19 infected shrimp wholesaler at a market in Samut Sakhon have also tested positive for the virus.
The shrimp market, meanwhile, has been closed for thorough cleansing.
The 67-year-old vendor's 95-year-old bed-ridden mother, her elder sister, aged 73, and her sister-in-law, 57, were found to be also infected, Dr Sophon Iamsirithaworn, director general of the Communicable Diseases Division, said on Friday.
The woman owns a stall at the Talad Klang Kung, or Central Shrimp Market, in Samut Sakhon and fell ill on Dec 13, with muscle pains and loss of sense of smell, he said.
She had not travelled abroad, Dr Sophon said. She was at the shrimp market every day, from 6am to 11am.
The woman was among 16 new Covid-19 cases reported on Friday by the Centre for Covid-19 Situation Administration.
On Dec 16, she went to a private hospital’s outpatient department around 6pm and was tested for Covid-19. Around 10pm, the test came back positive. The hospital then sent samples for testing at another lab, at a medical sciences centre, and the result also came back positive.
The woman was admitted to Samut Sakhon Hospital around 2am on Dec 17, Dr Sophon said. (continues below)
(Photo: Samut Sakhon PR office Facebook page)
Contact tracers found a total of 26 people were at high risk of infection. They were divided into four groups.
The first comprised seven family members, and three of them later tested positive.
The second consisted of three people who worked at her shrimp stall, her 39-year-old son and two Myanmar workers. Officials were awaiting their test results.
A third group comprised eight medical staff at the private hospital, and all tested negative.
The fourth group were eight people who worked at the shrimp market. Officials were awaiting their test results.
There were 139 people who were at low risk, he said.
Dr Sophon said the shrimp market had been closed for three days for cleaning.
He made no mention of how the stall owner may have caught the virus.
Amphai Harnkraiwilai, chairwoman of Mahachai fisheries development cooperative, on Friday made a point of explaining that the infected woman did not work at the province's Talad Talay Thai market, or Thai Seafood Market, which is popular with tourists.
Talad Talay Thai enforced health measures such as wearing of masks, temperature screening and hand washing, with hand sinks, hand gel and soap at six spots at the market, Ms Amphai told reporters. She wanted to clear up any confusion about the location, she said.