(NaturalNews) Whooping cough - otherwise known as Pertussis - is looking to make a rather nasty comeback this year. So much so that health officials are already warning of the danger.In fact, they say, the U.S. could face its worst year for whooping cough in nearly 50 years. Already the numbers of cases are rising so fast it's become a full-blown epidemic. What's worse, the epidemic may have been caused; in part, by a faulty, ineffective vaccine.So far some 18,000 cases of pertussis have been reported, thesaid recently, a figure that is more than twice the number seen at this point a year ago. At the current rate, the number of those affected for the entire year will be the highest since 1959; then, 40,000 cases were reported,said.Health officials say the disease has claimed the lives of nine children so far, and they are urging all adults, especially women who are pregnant and adults who spend a lot of time around children, to get a booster shot as quickly as possible."My biggest concern is for the babies. They're the ones who get hit the hardest," Mary Selecky, health department chief in Washington state, where outbreaks have been particularly high.Wisconsin and Washington have each reported more than 3,000 cases of whooping cough; other states with high numbers of cases include Arizona, Minnesota and New York.Pertussis cases have been rising steadily for a number of years, officials say, but nothing like this year's spike. The current unusual spike has led health officials around the country to look into why so many cases are suddenly occurring. Theories being floated include better reporting of cases and better detection methods, an evolution in the bacteria that causes the sickness, or problems with the vaccine AP said the vaccine that had been given to kids for decades was replaced in the late 1990s after concerns about rashes, fevers and other side effects surfaced. The newer version is considered to be safer but now there are fears it doesn't remain as effective over the long haul, according to Dr. Anne Schuchat, head of the CDC's immunization and respiratory disease programs.What the dramatic uptick in pertussis cases doesappear to be linked to; however, is an increasing number of parents in some of the most affected states exempting their children from vaccines. Washington state; for instance, has one of the highest vaccine exemption rates in the country, but CDC officials said most of the children who have come down with whooping cough were vaccinated.Pertussis is caused by bacteria that infect the top of the throat (pharynx), where it meets the nasal passages. The bacteria cause irritation in the throat, which in turn causes coughing that can sometimes be so violent as to injure ribs. The name "whooping cough" comes from the sound children make as they try to gasp for air during coughing episodes.The illness spreads easily between people; when someone afflicted with pertussis coughs, sneezes or otherwise spews forth little droplets of fluid, the bacteria are put into the air and are easily inhaled. After the bacteria infect someone, symptoms appear in one to two weeks.There are a number of indicators that suggest there could be a problem with the vaccine.For one, health officials in Washington say they are alarmed to see high rates of whooping cough among youngsters who are 13-14 years old.For another, whooping cough cases - once a common threat but which fell dramatically following the introduction of a vaccine in the 1940s, nearly to the point of becoming an afterthought in history - began to climb again in the 1990s. For about a quarter century before then, there were only about 5,000 cases reported each year.And in 2004 and 2005 cases rose to more than 25,000. After dipping for a few years, they rose to more than 27,000 in 2010, a year which saw the incidence of pertussis rise most in California.All of those factors have some investigators wondering if the vaccine thought to be safer is actually less effective.