Five babies have died in the current outbreak, which has seen 1,781 confirmed cases in England in Wales in the first six months of this year, the Health Protection Agency said. In the same period two years ago there were just 137 cases.
Most cases occurred in teenagers and adults, but there has been a sharp rise in the infection rate among babies under three months. Whooping cough, also known as pertussis, is a serious illness in the very young and can be fatal.
 The increase has been partly attributed to greater awareness among doctors, who are ordering more tests and producing more positive diagnoses. But waning immunity, even in those who have been vaccinated, is also likely to have contributed.
Increased rates of infection every three or four years are normal as diseases peak in cycles, but the current spike is the highest for two decades, doctors confirmed.
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