Scarlet fever strain makes deadly return
The serious scarlet fever cases this year have come from a dominant strain of the bacteria not seen for many years, a microbiologist said yesterday, as an 11-year-old boy remained in serious condition.
Dr Lo Wing-lok, who has extensive experience in the field, said this dominant strain of the bacteria may be the reason for a tenfold increase in the number of cases, jumping from 128 cases in 2010 to 1,534.
Lo said the scarlet fever occurring previously in Hong Kong was usually caused by group A streptococcus M1, but the infections contracted in the peak season last year and in the past few months were dominated by the M12 strain. 'That means children are less likely to have immunity over M12, increasing their chances of getting infected,' he said.
University of Hong Kong microbiology professor Dr Ho Pak-leung said M1, M3 and M12 were the usual types of bacteria transmitted in Hong Kong. But the serious scarlet fever cases of previous years were more commonly caused by the M1 and M3 strains.
'The fact that two children over 10 years old have contracted the bacteria may be due a cyclical return of the M12 [strain], and children in this age group do not have immunity to this type of bacteria,' Ho said.
'This means, a child above 10 years old may not be safe from scarlet fever as before, so parents need to remain alert to their children's health.'
He was referring to two cases announced by the Department of Health on Thursday: one in which a 14-year-old St Paul's Secondary School girl pupil died; and the 11-year-old boy, who was in intensive care at Pamela Youde Nethersole Eastern Hospital in Chai Wan.
St Joseph's Primary School in Wan Chai, which the boy attends, and St Paul's Secondary School in Happy Valley were closed for disinfection yesterday.
The boy developed flu-like symptoms on January 8, and was admitted to Hong Kong Adventist Hospital in Happy Valley for treatment. He was transferred to the Chai Wan hospital after tests found his platelet levels below normal, with his liver and kidney not functioning properly.
Dr Thomas Tsang Ho-fai, the controller of the Centre for Health Protection, said it was rare for a child aged above 10 to contract the bacteria, with 90 per cent of the cases normally seen in younger children.
Tsang said the government had launched an investigation and would look into whether a mutation had occurred in the bacteria making it more infectious or deadly.