Three Thais and a Chinese boy have been quarantined after they reported fevers shortly after arriving from the Chinese city of Wuhan, where a mysterious outbreak of viral pneumonia has been reported.
Preliminary laboratory tests found the three-year-old boy has a flu, while a 22-year-old Thai female student is suffering from a Respiratory Syncytial Virus (RSV) infection, said Department of Disease Control chief Suwanchai Wattanayingcharoenchai on Monday.
"We are still waiting on the test results of the remaining two patients -- a 24-year-old female student and a 44-year-old tourist," said Dr Suwanchai.
All of them are currently being treated and quarantined at Bamrasnaradura Infectious Diseases Institute in Nonthaburi's Muang district.
"At this stage, we are keeping a close watch on the four patients," Public Health Minister Anutin Charnvirakul said after visiting the institute on Monday.
"We've not found that they contracted the virus [found in Wuhan]."
The minister said they must be kept in isolation ward because of their symptoms and travel history to Wuhan, the capital of Hubei province and the most populous city in central China.
Since last month, at least 59 people have been diagnosed with mysterious infections which is believed to have originated in a seafood market in the city, according to Wuhan health officials.
The virus has not been identified, but the officials have said they are not bird flu, Middle East respiratory syndrome (Mers), severe acute respiratory syndrome (Sars) or adenoviruses, all of which cause a range of symptoms which include bronchitis, pneumonia and diarrhea.
Sars, which also originated in China, killed more than 700 people around the world in 2002 and 2003.
Mr Anutin insisted there is currently no concern about the spread of the new virus to Thailand, but warned Thais to delay their travels to high-risk areas.
The Department of Disease Control (DDC) has stepped up its anti-outbreak operations to "Level 2", following an increase in the number of infected people in China, as well as seven other suspected cases in Hong Kong and one in Singapore, Dr Suwanchai said.
Body temperature screening will be performed at major airports in Thailand served by flights from China.
Meanwhile, Phuket International Airport is beefing up its surveillance of incoming international passengers suspected of having flu-like symptoms.
The DDC has set up infrared thermal scanner at arrival halls at Suvarnabhumi, Don Mueang, Chiang Mai and Phuket airports to keep an eye out on passengers with respiratory conditions from cities where the mystery outbreak has been reported.