Australian sees sharp rise in whooping cough cases

A new strain of pertussis, or whooping cough, is believed to be responsible for a sharp rise in cases found in Australia.

Australia's prolonged whooping cough epidemic entered a disturbing new phase when a team of scientists from the University of New South Wales announced that an emerging genotype of the Bordetella pertussis bacteria may be evading the effects of the acellular vaccine.

The researchers said that the new strain has been seen in other countries, that which suggest that it has the potential to spark new epidemics. They warned the new genotype should be closely monitored.

"The prolonged whooping cough epidemic in Australia that began during 2008 has been predominantly caused by the new genotype of B. pertussis," a coauthor of the UNSW study, Ruiting Lan said. "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."

In 2011, Australia suffered 38,000 new cases of the illness, despite a relatively high rate of vaccine coverage.

"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," Lan said. "We need to look at changes to the vaccine itself or increase the number of boosters."

The researchers said that, to some degree, an increase in the number cases reported may be partly related to a recent improvement in diagnostic testing. They said that some mild or atypical cases in older children and adults may now be more likely to be correctly identified. This alone, however, does not account for the marked increase in hospital admissions due to the illness.