The Washington State Secretary of Health Mary Selecky has declared whooping cough is at epidemic levels and requested federal assistance. Washington has counted 1284 cases since the beginning of the year, ten times the number of cases at this time in 2011.
Wisconsin has also recorded nearly ten times the number of cases as last year, with nearly 1900 cases. In particular, Dane County reports 253 cases, more than the last four years combined. Montana has its own flood of cases in several different counties. No deaths have been reported in Washington, Wisconsin, or Montana.
Idaho has reported one infant death, but relatively few cases compared to the region. The reported death was a nine-week-old infant, too young to receive the pertussis vaccine.
Similarly, New Mexico had one infant death, a two-month-old who had received one vaccination (infants are not considered protected from whooping cough until they complete three shots at six months). This is the first infant death from whooping cough in New Mexico since 2005.
What is whooping cough? Why has this preventable disease resurged?
Whooping cough is an extremely infectious disease caused by the bacteria Bordetella pertussis (the medical term for whooping cough is pertussis). B. pertussis attach to the lining of the human respiratory system. Once there, they release a toxin that damages the lining and causes swelling. The swelling leads to coughing spells. The coughing spreads the bacteria to anyone near the infected host, continuing the transmission.
Whooping cough can be tricky to diagnose because it resembles the common cold in its early stages. Few people suspect anything more serious. It is only one to two weeks after initial infection that the characteristic violent coughing fits appear. The coughing can be so severe that it completely empties the lungs of air. This leads to a large inhalation of air and the “whoop” noise for which pertussis is nicknamed. (To hear the sounds of a child with whooping cough, click here).
And yet, the distinctive whooping noise is not always present. Teens and adults who have been vaccinated tend to experience milder illness, without the “whoop.” Likewise, infants don’t always have coughing fits, but instead may experience apnea (a pause in breathing).
Early treatment with antibiotics is especially important with whooping cough. After about three weeks, the bacteria are usually completely gone from the system, rendering the antibiotics useless. Unfortunately, the damage to the respiratory lining has already been done, so the cough persists. In fact, serious cases of illness can be accompanied by coughing fits for 10 weeks or more.
Prevention Through Vaccination
Because whooping cough is so dangerous for infants and can be hard to diagnose, prevention is very important. The best prevention is vaccination. Children should receive the DTaP vaccine, a series of shots beginning at two months of age that protects against diphtheria, tetanus and pertussis. Teens and adults can get the Tdap booster. Tdap vaccines are especially recommended for parents and grandparents of infants.
DTaP and Tdap are slightly different vaccines that target the same diseases. They differ in the concentration of components; young children receive DTaP, with higher diphtheria and pertussis doses, to make sure they develop the proper immune response.
Both vaccines use acellular pertussis (hence the “ap”), meaning the vaccine contains selected antigens instead of a whole B. pertussis cell. The choice to use selected antigens instead of the whole cell lowers the risk of side effects.
An antigen is a substance that evokes an immune system response, specifically, the production of antibodies (a specific protein in the immune system). You can think of an antigen as a key protruding from the surface of the pertussis bacteria and an antibody as the lock that fits that key. Just like the key to your car does not unlock your front door, each antibody will fit a specific antigen. If pertussis bacteria enter the body in the future, antibodies will “lock” onto the pathogen and tag it for the immune system to destroy.
Lack of Vaccination Driving the Epidemic
If there is an existing and effective vaccine against whooping cough, why are so many states experiencing outbreaks? What is driving this epidemic?
To a certain extent, pertussis is a cyclical disease, meaning occasionally there will be increases in cases. A further possible explanation points at budget cuts at the state and local health departments that slashed prevention programs.
But perhaps the most at blame are the high vaccine exemption rates (the percentage of parents who opt out of routine vaccination for their children). According to Selecky, Washington had “the easiest opt-out law in the nation” and as a result, exemption rates of around six percent. Within the past year, the state legislature passed a law requiring parents to prove they consulted a doctor before refusing vaccination; hopefully, this act will help increase vaccination rates.
Similarly, New Mexico officials identified increasing exemption rates as a possible cause behind their uptick in cases. Exemptions have tripled since 1999, with nearly 3400 claiming vaccine exemptions. It appears that pertussis cases are following that trend: New Mexico recorded 85 cases in 2009, 274 in 2011, and so far in 2012, there are already 112 cases.
Whooping cough is a perfect demonstration of the importance of widespread immunity in a population. The disease is most dangerous to infants who are too young to be fully vaccinated. In order to protect the very young and those who are medically unable to receive vaccinations, it is up to the rest of the community to provide ‘herd immunity.’ If most people are immune, the disease will not circulate in the population, and even those who are vulnerable to infection will be relatively protected.
For infants specifically, health professionals promote the idea of “cocooning”, or surrounding the infant with people (parents, relatives, family friends) who are already immune to the disease.
Public health officials across the country are asking individuals to check with their doctors and ensure they have already been vaccinated against whooping cough, or ask if they are a good candidate for vaccination.