One of three children whose deaths from flu-like symptoms caused a citywide closure of schools last year died of heart inflammation, probably caused by a virus, the Coroner's Court heard yesterday. Pathologist Anthony Lo Wing-ip said that although an autopsy found no traces of a virus in the body of Or Ho-yeung, aged two, his blood contained a high level of lymphocytes, a type of white blood cell. As the body produced such cells to fight viruses, there was close to a 100 per cent chance that a virus had caused the acute inflammation of the heart muscle, also known as myocarditis, he said. Dr Lo was presenting the autopsy report to the joint inquest into the deaths of Ho-yeung and the two other victims, aged three and seven, which began yesterday. He said Ho-yeung's virus could have originated from the intestine, noting the boy had vomited before his death, but said that was just a possibility. The boy's father, Or Ming-tung, told the inquest Ho-yeung developed a fever and cough on February 21 and began vomiting on the 25th. Mr Or took his son to a private doctor, who prescribed antibiotics and advised Mr Or to take the boy to Prince of Wales Hospital if his condition worsened. When it did, he went to the hospital on the 25th. Dr Michael Young Lap-wai told the court he admitted the boy with a diagnosis of gastroenteritis. Edmund Nelson, a doctor with the hospital's paediatrics department who helped treat Ho-yeung, said the boy vomited once but his vital signs were satisfactory, except for slightly abnormal blood pressure, which later returned to normal. But in the afternoon the day after admittance, Ho-yeung's situation suddenly worsened, with no detectable blood pressure at 3.15pm. Despite emergency rescue attempts and a regime of drugs to return normal blood flow and pressure, the boy died an hour later, Dr Nelson said. Mr Or said doctors should have placed his son on a saline drip immediately after admitting him and paid more attention when the boy vomited a second time. Dr Nelson, Dr Lo and other doctors who testified yesterday said a saline drip would have made no difference. The inquest, split into three parts with one for each child, continues today into the death of three-year-old Ho Po-yi, who died on March 1.