Australia's prolonged whooping cough epidemic has entered a disturbing new phase, with a study showing a new strain or genotype may be responsible for the sharp rise in the number of cases.
A team of Australian scientists, led by the University of New South Wales (UNSW), believe this emerging new genotype (called prn2-ptxP3) of the Bordetella pertussis bacterium may be evading the protective effects of the current acellular vaccine (ACV), and increasing the incidence of the potentially fatal respiratory illness, according to the study published in The Journal of Infectious Diseases.
The new genotype also has been detected in other countries, suggesting it has the potential to spark epidemics elsewhere and should be closely monitored, the researchers warn.
"The prolonged whooping cough epidemic in Australia that began during 2008 has been predominantly caused by the new genotype of B. pertussis," said one of the study authors, Associate Professor Ruiting Lan, of the UNSW School of Biotechnology and Biomolecular Sciences.
"The genotype was responsible for 31 percent of cases in the 10 years before the epidemic, and that's now jumped to 84 percent a nearly three-fold increase, indicating it has gained a selective advantage under the current vaccination regime.
"The vaccine is still the best way to reduce transmission of the disease and reduce cases, but it appears to be less effective against the new strain and immunity wanes more rapidly. We need to look at changes to the vaccine itself or increase the number of boosters," Associate Professor Lan said.
Last year about 38,000 cases of the life-threatening disease were reported nationally, despite Australians having a relatively high vaccine uptake.
The authors said the increase in the number of whooping cough notifications may be partly due to recent improvements in diagnostic tests, which means that mild or atypical cases in older ch
|Contact: Ruiting Lan|
University of New South Wales