evidence: Whooping cough, or pertussis, is very contagious and mainly affects infants and young children. Whooping cough is caused by a bacterium called Bordetella pertussis. The illness is characterized by coughing spells that end with a characteristic "whoop" as air is inhaled. Whooping cough caused thousands of deaths in the 1930s and 1940s. With the advent of a vaccine, the death rate has declined dramatically. Pertussis vaccines are very effective. However, if pertussis is circulating in the community, there is a possibility that even a fully vaccinated person could catch the disease. Babies who are too young to receive the vaccine are also at very high risk of catching pertussis. The illness can be very serious, even sometimes fatal, in young infants. Many babies infected with pertussis have caught it from an adult.