In more than 50 years, California has been hit by the largest whooping cough outbreak. This is confirmed by death of six infants under-three months of age dying of cough.

Booster shots are being recommended by California health officials are for nearly everyone in the state. Those who are being urged more to get the shots are parents, and health care workers, and anyone who may come in contact with babies.

This year in California about 1500 people have been diagnosed with whooping cough and according to state health officials, this is five times the normal level for this time of year.

Another 700 cases are being investigated by doctors and reports state that many cases go unreported often.

Gilberto Chavez, chief of the California Department of Public Health's Center for Infectious Disease, said, "This has the potential to become very huge. But we are at a point where we can contain it."

Chavez says that babies do not have natural immunity to whooping cough, which is also known as pertussis and this made it important to save babies from getting it.

Experts said that the only way to keep away babies from getting infected was vaccinating everyone around them.