Remember the last time you had a regular cold followed by weeks of annoying, dry coughing? Did it ever cross your mind that your problem might be whooping cough? Most likely, neither you nor your doctor gave the diagnosis a minute’s thought. Isn’t whooping cough is one of those childhood diseases, like measles and chicken pox, that immunizations have largely defeated? Yes and no. Yes, whooping cough is a serious illness in babies and toddlers, but it also afflicts adolescents and adults of all ages. And no, the disease has not gone the way of the dinosaurs, though immunization of babies and toddlers has dramatically cut morbidity and mortality rates from the infectious illness.

What is whooping cough?

Whooping cough is a highly infectious respiratory disease caused by the bacterium called Bordtella pertussis. The symptoms of whooping cough begin a week or so after exposure to someone who has the illness. At first, the stuffy, runny nose and mild cough, with little, if any, fever seem like ordinary cold symptoms. But within ten to fourteen days paroxysms of more severe, unproductive coughing begin. Coughing lasts, on average, six weeks. While coughing paroxysms are the signature feature of the illness in all age groups, older children and adults may lack the “whoop” on intake of breath that gives the illness its name.

Babies can die; adults break ribs 

In babies and children coughing bouts are frequently followed by vomiting. Infants can quickly develop respiratory distress and pneumonia, and most whooping cough fatalities occur in babies. Older children and adults suffer less severe disease, but the intensity of coughing can make life miserable for weeks, and can lead to hernias and broken ribs. Antibiotic treatment with erythromycin works, but only if the disease is suspected and confirmed early – before the worst of the coughing begins.

Many cases go undiagnosed

Many cases of whooping cough go undiagnosed because people do not seek medical help, or because the diagnosis is unsuspected. Even when whooping cough is suspected as the cause of a chronic cough, accurate laboratory diagnosis is difficult. By the time persistent cough finally brings people to the doctor, a throat or nasal swab may not pick up any bacteria. In addition, routine laboratory culture methods don’t work for pertussis bacteria like they do for streptococcal infections. Proof of infection can be inferred by the presence of blood antibodies against the bacteria, but blood tests to measure titers of are expensive and seldom done.

Vaccine development cut the death rate

Whooping cough occurs worldwide and causes an estimated 300,000 deaths per year across the globe. In the United States, death rates were in the 5,000-10,000/year range between the 1920s and 1940s, but the development of a pertussis vaccine reduced that toll enormously in the latter half of the 20th century. Recently, however, increasing numbers of whooping cough cases are being reported. In 2010 California declared a whooping cough epidemic based on 9,477 confirmed, probable and suspected cases. Washington State did the same in 2012. By that year, 48,000 confirmed cases were reported across the country. At the height of the California epidemic, there were 10 deaths – too many for a preventable disease, but a far cry from the tolls of the past.

Natural cycles, parental backlash and a  changed vaccine 

Bordtella pertussis has never disappeared from its niche in the human population, and several factors are at work in the recent, apparent increase in rates of infection. Foremost is a natural bacterial population cycle. Whooping cough bacteria seem to increase their numbers in 3-5 year cycles which probably correspond to naturally declining immunity in a population as children get older. This natural variation has coincided with some parental backlash against vaccinations because of fears that they do more harm than good, though childhood immunization rates as a whole are still very high. A third factor may be weaker population immunity because of alterations made to whooping cough vaccine in the 1990s.

Clearly, the original pertussis vaccine, derived from whole, dead pertussis bacteria and delivered as part of the first series of a baby’s shots, helped produce immunity sufficient to make death rates among babies drop dramatically. But in the early 1990s, the formulation of the vaccine was changed to decrease adverse responses to it – responses like fever, swelling at injection sites and rare cases of encephalitis. That change may be responsible for lessened immunity and more whooping cough cases among older schoolchildren. It also raised the number of shots that must be given over several months to achieve immunity in a baby.

Should drug companies fund vaccine research?

Some people who worry that too many vaccines are now being required and are less effective than advertised claim that the makers of the vaccines are anxious to find reasons to give booster shots to as many people as possible. Indeed, the largest and most influential of the scientific groups studying whooping cough – the Global Pertussis Initiative (GPI) – is funded by vaccine makers. But Dr. James D. Cherry has been studying whooping cough for several decades and maintains that the monetary sponsorship by pharmaceutical companies is necessary. Compiling data about infection rates and vaccine efficacy is expensive and surprisingly difficult. The prevention and treatment of infectious diseases depend on accurate assessment of disease rates and currently public health surveillance and reporting is hampered by lack of uniform standards for the diagnosis of whooping cough, especially in older children and adults. In addition, the development of vaccines is extraordinarily complicated and expensive, and will be of increasing importance as antibiotic resistant bacteria continue to evolve and thrive.

Who needs to be concerned about whooping cough?

Whooping cough is of most concern to people who work around and live with small babies who are too young to have completed their series of early DTaP immunization shots (against diphtheria, pertussis and tetanus). The booster vaccination has little risk and is probably advisable for all adults who are in regular close contact with susceptible infants. In the meantime, if you develop one of those miserable chronic coughs after a cold, stay away from vulnerable babies who have not yet had all their shots.