A 72-year-old Singaporean retiree who had been sent to Raffles Hospital on Wednesday because of a heart condition was among four new community cases yesterday. The man, who was asymptomatic, tested positive for Covid-19 the next day, and his serology test also came back positive - indicating that he could be shedding minute fragments of the virus RNA from a past infection that are no longer transmissible and infective to others, said the Ministry of Health (MOH). "But given that we are not able to definitively conclude when he had been infected, we will take all the necessary public health actions as a precautionary measure," it said.