New statistics show that the United States is in the midst of the worst outbreak of pertussis, or whooping cough, in fifty years. Case reports have doubled between 2011 and 2012, with nearly 18,000 cases reported this year already.
Wisconsin, New York, Minnesota, Arizona, and Washington have seen particularly high numbers this year.
Experts are still trying to uncover the reason behind this spike in cases. Some possible explanations include improved detection and more diligent reporting, evolution of the bacteria, or the use of a less effective vaccine.
The pertussis vaccine administered today has been in circulation since the late 1990s, when concerns about side effects from the previous drug persuaded doctors to switch. However, it is possible that the current vaccine is not as effective as the earlier version, and may be leading to higher rates of infection.
Some have hypothesized that an increase in the number of parents opting out of or altering vaccine schedules has contributed to the pertussis outbreak. Children who do not receive all the shots in the pertussis series are at greater risk of infection themselves and can transmit the disease to others. However, experts argue that this new practice does not seem to explain the pertussis outbreak since most children have in fact been vaccinated for pertussis: the CDC estimates that 84 percent of children under three have received the vaccine. Moreover, the majority of this year's pertussis patients were infected with the disease despite being vaccinated.
More likely is the possibility that adults and adolescents are not renewing their vaccines and are thereby putting children at risk of infection. Experts at the CDC estimate that less than 70 percent of teens and only eight percent of adults have received a pertussis booster. Because infants cannot receive the vaccination until two months of age, it is crucial that adults—particularly pregnant women and people who work with children—receive their booster shots. Pertussis in young children may be particularly severe; more than half of children under age one who are infected with pertussis require hospitalization.
While the pertussis vaccine is not always completely effective, people who are vaccinated will usually contract a milder version of the disease, if at all. Before the development of the vaccine in the 1940’s, 175,000 individuals were infected each year. Today’s infection rates range from 1,000 to 27,000 cases annually.
Pertussis is caused by the bacterium Bordella pertussis and is sometimes called whooping cough because of the sound that patients make as they gasp for air. The bacteria are transmitted by an infected person’s cough or sneeze. The disease, which causes flu-like symptoms and coughing fits, can be treated with antibiotics. However, experts at the CDC recommend the pertussis vaccine as the best way to prevent infection.
Previous Disease Daily articles cover pertussis infection and challenges to high vaccination rates.