The US is going through its worst case of whooping cough outbreak in more than five decades, with a rising number of cases in several states. Health officials are expressing concern that the pattern indicates a problem with effectiveness of vaccine.
Health officials say nine children have died so far.
The Associated Press reports that the Centers for Disease and Control and Prevention (CDC) said Thursday that nearly 18,000 cases have been reported so far this year. If the current rate continues for the rest of year, the number of cases for the entire year will be the highest since 1959 when 40,000 cases were reported.
Health officials have recommended booster shots for adults, especially pregnant women, and other adults who live with children or spend time around them.
According to Reuters, health officials say they are most concerned about the risk to babies. Dr. Anne Shuchat, head of CDC's immunization and respiratory disease programs, said, "It's most dangerous for babies. Preventing infant deaths from the disease is our primary national goal."
Mary Selecky, chief of the health department in Washington, said: "My biggest concern is for the babies. They're the ones who get hit the hardest."
Reuters reports that Washington state declared an epidemic in April. The number of cases in Washington has tripled since April, with 1,132 cases reported by the end of the month.
Washington and Wisconsin have reported more than 3,000 cases. Other states, including New York, Minnesota and Arizona have also seen high numbers of cases.
Whooping cough, also known as pertussis, is highly contagious. The illness usually begins with cold-like symptoms, including runny nose, congestion, fever, and a mild cough. It affects people of all ages but infants and children are especially vulnerable. The disease derives its name from the "whooping" sound the child makes as he or she gasps for breath.
In the past, whooping cough was rampant with hundred of thousands of cases a year. But following introduction of an effective vaccine in the 1940s, the rates dropped dramatically. But after the illness was thought to have been almost eradicated the rate began increasing again in the 1990s.
The Associated Press reports that the number of cases reported in 2004 and 2005 was greater than 25,000. The was a brief pause in the trend but it jumped suddenly to 27,000 in 2010 with California being worst hit.
Health officials say although there has been a gradual increase in the incidence of whooping cough over the years, the rate increased very sharply this year. Health researchers are investigating the possible reasons for the sudden spike and have suggested several reasons, including better detection and reporting, and emergence of new strains of the disease causing pathogen.
According to The Associated Press, some parents in states such as California have fought to be exempted from regulations that require them to immunize their children before enrolment in school. Washington state has one of the highest exemption rates in the US. The CDC, however, says exemptions do not appear to be the main factor causing the outbreak because most of the children who reported with the illness had already been vaccinated.
There is a growing concern that the vaccine currently in use could have become less effective. The Associated Press reports that the whooping cough vaccine was replaced in the late 1990s after concerns were raised about certain side effects, including rashes and fevers. According to Shuchat, a new vaccine was introduced. But now there are concerns that it may not be an effective vaccine for long term prevention of the illness.
Reuters reports that Mary Selecky, Washington Health Secretary, said that an increase in the incidence of whooping cough among 10-year-olds, 13 and 14-year-old adolescents, indicates that the immunity boosting effect of the new vaccine could be wearing off earlier than expected.
The earlier vaccine used whole cell parts made of killed pertussis bacteria, but the new DTaP uses only small acellular bacteria pieces, not the whole bacteria cell, Donn Moyer, Washington state Health Department spokesman explains.
CDC officials say they will start investigation to "analyze our data for cases among 13- to 14-year-olds to see what can be learned about disease rates and vaccination status."
The Associated Press says government recommends that children should get vaccinated in five doses. The first shot at 2 months of age and the final between 4 and 6. A booster shot is recommended for 11 and 12-year-olds.
Officials statistics show that about 84 percent of 3-year-olds have received the recommended number of shots, but less than 70 percent of US adolescents get all their shots.
The CDC advises people to see a doctor if they have a prolonged or severe cough. The disease is treated with antibiotics.
CDC advises that the earlier the better.