A dramatic increase in the number of whooping cough cases in the North Coast Area of New South Wales has concerned health officials.
The increase has prompted the North Coast Area Health Service (NCAHS) to issue a warning to the public to be on the alert for symptoms.
Whooping cough (pertussis) is an infection of the respiratory system characterized by severe coughing spells that end in a "whooping" sound when the person breathes in.
Before a vaccine was available, pertussis killed thousands each year but the vaccine has dramatically reduced the number of deaths.
Although whooping cough can occur at any age, it's most severe in un-immunized children and in infants under 1 year of age.
In recent years, the number of cases has started to rise again mainly affecting infants younger than 6 months old before they are adequately protected by their immunizations, and children who 11 to 18 years old whose immunity has possibly weakened.
Paul Corben, the director of North Coast Public Health, says the current outbreak has affected all age groups in particular children under 10 years of age.
Mr Corben said in the first two months of this year 60 cases of whooping cough were reported, compared with 129 cases for all of 2007.
In order to help prevent the serious illness, the NCAHS has urged parents to ensure that young babies and children are fully vaccinated.
They are also recommending that anyone who may have contact with small children, such as parents or grandparents, or people working with small children including health care and childcare workers, should receive a booster vaccine available from their doctor.
Experts say it is very important that people are treated early to stop the spread of the disease.
They say children under six months of age and anyone who has not received three doses of whooping cough vaccine will not have been fully vaccinated and remain very vulnerable to whooping cough.
Symptoms can include a runny nose, tiredness, a mild fever, and coughing bouts, the coughing bouts are followed by a big deep gasp that sometimes produces a whooping sound and vomiting can also occur.
Pertussis vaccinations are given at two, four and six months with a booster at four years.
An additional pertussis/diphtheria/tetanus vaccine is available for teenagers free of charge at the age of 15 years.
As immunity following vaccination or disease is not life-long, older children and adults, as well as those who have never received any vaccines, are susceptible to the infection and re-infection.
The last epidemic in Australia was in 2001 when cases rose sharply; it caused 6 deaths.
Officials say whooping cough remains a challenge to control because while immunised children are protected, adolescents and adults continue to spread the infection, often without realising it, immunisation rates were low in the past and the vaccine wears off.
The situation is the same in both the U.S. and Britain where according to the Department of Health, cases of whooping cough have nearly trebled since 2003.
An outbreak in 1991 involved 5,000 cases and provisional figures suggest there were as many as 1,071 in 2007 in the UK.