The actual number of new daily Covid-19 infections may be as high as 50,000 compared with the official Ministry of Public Health figures, Nitipatana Chierakul, a respiratory disease expert with Siriraj Hospital, said on Thursday.
However, most patients are only showing mild symptoms, he said.
The ministry on Thursday recorded 2,257 new "confirmed" Covid-19 cases with 28 deaths, with 770 patients being treated for lung infections in hospitals.
Considering the number of positive Covid-19 antigen test results counted and reported by the ministry from July 3-9, the average number of infections via antigen testing alone should be about 20,000 per day, said Assoc Prof Dr Nitipatana, head of the division of respiratory diseases and tuberculosis at Mahidol University's Faculty of Medicine at Siriraj.
However, while Thailand is now in a transition from handling Covid-19 patients using a central management system to resuming normal healthcare operations, in which new Covid-19 patients are required to instead seek treatment under their healthcare schemes, it is estimated that about one-third of the daily infections go underreported, he said.
This means about 30,000 new cases are possibly found via Covid-19 antigen testing each day, he said.
Still, since most new patients only show mild, or even no symptoms, of infection, many more may choose not to report positive antigen results to health authorities, he said.
As such, the total number of new infections has probably reached 50,000 a day, which appears stable when compared with the estimated figures shown from June 26 to July 2, Dr Nitipatana said.
Two other medical experts on Thursday shared similar views.
Yong Poovorawan, chief of the Centre of Excellence in Clinical Virology at the Department of Paediatrics of Chulalongkorn University's Faculty of Medicine, described the current outbreak as Thailand's sixth wave.
The BA.5 subvariant of Omicron is mainly responsible for recent flareups, which are expected to peak late this month and remain high throughout next month before they begin dropping during the next school break, Dr Yong said.
Dr Yong estimated the rate of new Covid-19 patients requiring hospitalisation is about 10% of all new infections while the death rate is about 1% among those who receive treatment in hospital, or about 0.1% of all new infections.
He expressed optimism these numbers would fall to be in the same range as severe influenza and related deaths.
Dr Yong warned the Covid-19 death rate would likely be considerably higher in this wave considering the higher rate of patients suffering lung infections.
At-risk groups should get antiviral medication as soon as possible to cut the risk of them developing severe illness while the administration of boosters should be scaled up, he said.
Dr Manoon Leechawengwongs, a pulmonologist at privately run Vichaiyut Hospital, said the number of new daily infections recorded by the ministry is low because it only counts cases confirmed by RT-PCR testing.
The rising number of Covid-19 patients suffering lung infection who require a respirator is a key indicator of the current situation, he said, adding BA.5 poses a new risk as it is capable of evading immunity.