Patients with severe cases of swine flu are reacting poorly to antiviral drugs such as Tamiflu, and they are more likely to develop inflammatory infections even though the virus in their body is weakening, the latest University of Hong Kong study shows.
The university also estimated that more than 300 people could die in the second wave of the pandemic, which is expected to peak next month.
The findings were announced yesterday, as the government launched its free vaccination scheme for people in five high-risk groups. A total of 1,528 people were inoculated.
HKU scientists compared 37 severely ill swine flu patients with 37 mild cases. All the 13 patients who died had severely damaged lungs, and some had blood clots, inflamed hearts or haemophagocytosis, a condition where white blood cells become so active that they attack healthy cells. White blood cells usually defend the body against infections.
'Even when they had recovered, we are uncertain how much of their lung function had been damaged,' said Professor Yuen Kwok-yung, head of the university's microbiology department, who led the study.
He said antiviral drugs such as Tamiflu and Relenza worked best when taken within 48 hours of the onset of symptoms. But the people they studied who had the most severe cases of swine flu sought help only five to seven days later, meaning the drugs were no longer useful. The virus slowly weakened in the body, he said.