The American lived in Singapore for eight years on an EP, from 2008 to 2016.
Those records are in the possession of Mikhy K Farrera Brochez, an American who was deported from Singapore last April after he was convicted of fraud and drug-related offences and sentenced to 28 months' jail.
The ministry said Brochez worked in Singapore as a lecturer for a period before he was jailed for several drug and fraud-related offences and deported a year ago.
The MOH said he'd been aided in criminal activity by his partner, a Singaporean doctor who was formerly head of MOH's National Public Health Unit.
An HIV-positive U.S. expat now on the run has leaked the HIV-positive status of 14,200 people - plus their contact details and the names of some of their sex partners - from a Singaporean health database.
The sensitive information included names, identification numbers, phone numbers, addresses and HIV test results, MOH said in a press release. The name, identification number, phone number and address of 2,400 people identified through contact tracing up to May 2007 was also included.
"I'm sorry that one of our former staff who was authorised to have access to confidential information in our HIV registry appears to not have complied with our security guidelines", Health Minister Gan Kim Yong said at a Monday news conference, Singapore's Today Online news website reports.
This latest incident comes months after a major cyberattack on Singapore's government health database saw hackers steal the medical information of some 1.5 million people, including that of Singaporean Prime Minister Lee Hsien Loong.
The information relates to 14,200 individuals who were diagnosed with HIV up to January 2013. It said it lodged another police report and notified the affected individuals. The ministry said it then worked with "relevant parties" to disable access to the information.
Kamala Harris raises eyebrows at televised town hall
"I'm running for president because I love my country", declared the 54-year-old, whose father is Jamaican and mother is Indian. Kirsten Gillibrand (D-N.Y.), have also entered the race, while others, including former Vice President Joe Biden and Sen.
He is not now in the city-state, the ministry said, adding that authorities were seeking assistance from their foreign counterparts.
"Police will not hesitate to take stern action, including prosecution, against those who have breached the OSA". His partner previously had access to the HIV registry for his work, it said.
Meanwhile, Ler was charged in 2016 under the Penal Code and Official Secrets Act (OSA).
May 2018: After Farrera-Brochez had been deported from Singapore, MOH received information that Brochez still had part of the records he had in 2016.
In September past year, he was convicted of abetting Brochez to commit cheating, and also of providing false information to the Police and MOH.
"The information has been illegally disclosed online", it said.
Only when the police notified MOH last week (22 Jan) that the confidential information possessed by Farrera-Brochez has been leaked online that MOH chose to inform the public yesterday.
March 2019: Ler's appeal against his 24-month sentence to be heard.
He was convicted in September past year of abetting Farrera-Brochez to cheat and of providing false information to the police and Ministry of Health (MOH).