The United States is in the middle of its worst whooping cough (aka pertussis) outbreak in over half a century, but few states have been hit as hard as Washington. This graph, released just a few days ago by the CDC, compares the state's pertussis cases in 2012 against those documented in 2011 — and the difference is downright staggering.
The graph plots the number of cases of pertussis by week of onset from January 1, 2011 through June 16, 2012. See those relatively short, stubby looking grey bars? Those correspond to pertussis cases documented in 2011. The gigantic, dark-blue bars? That's what Washington is facing today. Between January 1 and June 16 of this year, a total of 2,520 pertussis cases have been reported. By this time last year, the state had seen just 180 cases. That translates to a mind-boggling 1300% increase.
Put simply: things are very, very bad. In fact, they're even worse than state officials predicted they would be. Back in May, Washington's health department spokesman Tim Church warned that the state risked ending 2012 with 3,000 pertussis cases if steps were not taken to "stem the tide" of infection (3,000 pertussis cases would be the highest number Washington has seen since the 1940s). Fast forward to today, and the 3,000-case threshold seems not just likely, but inevitable.
There is a very real chance that Washington's pertussis cases will continue to skyrocket in the months to come. Notice how 2011's grey bars get taller and taller as the year proceeds; 786 (81%) of Washington's 966 pertussis cases in 2011 were reported during the second half of the year. If the number of cases in 2012 continues along a similar trajectory, the results will be nothing short of devastating. (It's worth pointing out that the drop in 2012 numbers in recent weeks, overlaid in the graph up top by a shaded bar, corresponds to a lag during which additional cases likely occurred during 2012, but had not yet been reported to Washington's Department of Health).
Explanations vary. On one hand, the pertussis bacterium could be developing a resistance to the childhood vaccine (DTap) and adolescent/adult booster (Tdap); but Washington's rate of infection is still ridiculously high.
Look at it this way: the country is in the middle of its worst outbreak in half a century, so pertussis infections are up across America; yet Washington's pertussis incidence is still more than seven times that of the national average (second only to Wisconsin). That, say experts, points to a more pernicious problem: the anti-vaccination movement.
So-called "antivaxxers" have an unusually firm foothold in the state of Washington. Last year, The Seattle Times reported that "Washington [state] parents are choosing not to vaccinate their kindergartners at a rate higher than anywhere else in the country."
"When the vaccination rates drop, everyone becomes more vulnerable to infectious diseases," writes Steven Salzberg, a professor at Johns Hopkins School of Medicine, in a recent blog entry. He continues:
When more than 90% of the population is vaccinated, we have "herd immunity" — this means the disease can't spread because there aren't enough susceptible people in the community. So the high rate of vaccine refusal in Washington makes it easier for whooping cough (and other diseases) to spread.
Thankfully, state officials in Washington believe in vaccines, and have spent upwards of a million dollars on a comprehensive vaccination campaign. The Seattle Times reports that the Department of Health has ordered 41,400 doses of vaccines since last month, and that counties are working with local health agencies and pharmacies to distribute them at a fraction of the normal cost of 60 dollars.
"Most insurers cover the cost of the vaccine, reports Seattle Times' Kibkabe Araya, "But with the state-supplied vaccine, the price drops to a $10 to $15 service fee if the underinsured or uninsured customer can pay. Otherwise, the fee is waived."
Remember: Washington is just one part of a nationwide pertussis outbreak, the likes of which the U.S. hasn't seen in fifty years. Pertussis is a nasty, nasty disease. It's highly contagious, typically manifests in the form of a violent, uncontrollable cough that can persist for months on end (it's also known as the 100 days' cough), and is fatal in an estimated one in 100 infants. With cases on the rise, you owe it to yourself and those around you to talk with your doctor about getting vaccinated, or getting a booster.
- Information on pertussis vaccination from the CDC
- The CDC's comprehensive Morbidity and Mortality Weekly Report on Washington's pertussis Epidemic
- The latest information on Washington's Pertussis Epidemic, from the Washington State Department of Health
- Steven Salzberg addresses the impact of Anti-vaccination propagandists at Genomics, Evolution, and Pseudoscience
- Bad Astronomy's Phil Plait weighs in on antivaxxers