By William Murtaugh, specialist, HIV/TB programs, Infectious Disease, APHL
“Defeat TB: Now and in the Future.” This was the first theme of World Tuberculosis Day declared by the International Union Against Tuberculosis and Lung Disease (IUATLD) 32 years ago today in 1982, and 100 years after Dr. Robert Koch announced his discovery of the bacteria that cause tuberculosis disease (TB).
Well, the future is March 24, 2014, and TB has not yet been defeated. But year after year, and theme after inspiring theme, the global public health community still proclaims a call to arms, aiming to inspire the world to take up the cause of TB elimination.
In the United States, the burden of TB is very low relative to many parts of the world. Why then should we be concerned with Mycobacterium tuberculosis, the obligate bacillus demanding our attention today?
It is common to cite TB statistics to emphasize the disease’s impact and the progress toward its elimination. Indeed any TB expert can pull some staggering historical numbers out of his or her pocket. But reconciling unembellished phrases like “billions infected,” “millions of new cases,” “over a million deaths,” with the experience of those of us average Americans who’s TB “exposure” is limited to news bulletins on World TB Day, is challenging. For us, World TB Day serves as a gentle nudge that the disease is still a threat, and the fight for its elimination continues. Yet while I would be remiss if I did not mention that the United States has seen 21 years of consecutive decline in annual TB cases, I must contend that TB awareness is particularly important here in the United States because of the country’s low TB burden.
Lest we take our progress for granted, repeating the mistakes of the 1980’s and 90’s, it’s important to remember the consequences when the health system falters. But for the one day, hour or minute that we consider World TB Day, let’s recognize that our progress to date has been achieved through the quiet efforts of a public health system that functions not one day, but all year long.
A TB outbreak in April 2013 exemplifies this point. Along the shores of Lake Michigan sits Sheboygan, WI, a city whose description could be mistaken for a Garrison Keillor monologue “where all the children are above average” and so too are its TB case rates. This Midwestern community learned the hard way that the damaging effects of TB can still be very real.
Prior to 2013, Sheboygan County typically saw fewer than three TB cases per year. Known as the “Malibu of the Midwest” for its lake surfing competition (the largest in the world in fact), Sheboygan was a place more familiar with the phrase “Hang Ten” than “MDR-TB.” Then in mid-April, the Sheboygan County Health Department was notified of a suspected TB case that would lead to an outbreak that would engage its resources and generate national media coverage for the remainder of the year.
Before it was over, the outbreak would cross the county and spread through multiple generations of a single family, school children and healthcare workers. It would lead to a case of MDR-TB, 11 additional cases of active pulmonary TB disease and 38 latent (non-symptomatic, non-contagious) TB infections. Over $6 million in state and federal funds ($4.7 million state, $1.4 million federal) would be expended to cover costs associated with outbreak investigation, testing, treatment and prevention measures.
Because TB is uncommon in the US, doctors may not consider it as a potential diagnosis. The first (i.e., index) case in the Sheboygan outbreak sought medical care for symptoms at least eight months before receiving a diagnosis of TB. What should have been a straightforward case – in which a suspected TB patient is diagnosed, treated and transmission prevented – led to eight months of transmissions.
Once TB was finally proposed as a diagnosis, the Wisconsin State Laboratory of Hygiene (WSLH) responded quickly, performing initial screening in two days and confirming diagnosis in less than two weeks. This diagnosis kick-started the TB control system into high gear. The patient was isolated and treated, and contact investigations were initiated to find related cases.
Next the WSLH assessed the standard drug regimen to determine if it would prove effective with this patient. With assistance from the Centers for Disease Control and Prevention (CDC), the lab identified multi-drug resistant TB (MDR-TB) a category of infection that involves resistance to multiple drug therapies, is more difficult and expensive to treat, and holds a higher risk of death — as the cause of the patient’s illness. Now the concern was, “Had other patients been exposed to MDR-TB in the past eight months?”
More specimens began arriving at the local laboratory near Sheybogan, which quickly exceeded its capacity. With the threat of an MDR-TB outbreak, a solution was needed quickly. Enter the integrated public health laboratory system! State and local laboratories coordinated with the community hospital in Sheboygan and decided jointly that all specimens from TB suspects would go to the WSLH.
As diagnosis after diagnosis of active pulmonary TB was confirmed, the state TB Control Program wanted to know if all these cases were part of the same outbreak. While this may seem an obvious “YES!”, not all TB is created equal. Numerous strains of TB are continually in circulation. Without identification of the specific strain, public health officials could not understand the chain of transmission, and without this information, they could not control the outbreak.
Through a CDC initiative designed to strengthen national response to TB outbreaks, state public health laboratory in Michigan performed complex testing to uniquely identify each strain of M. tuberculosis (called genotyping). They determined that the MDR-TB patient was infected with two different strains of TB, one of which was not MDR-TB. The state laboratories confirmed that other TB strains also belonged to the outbreak. None of these strains, however, were MDR-TB and therefore were more easily treated.
Not bad for a low burden TB setting.
Sheboygan’s story reminds us that TB outbreaks can happen anywhere. Yet if an outbreak does occur in our community we can look with confidence to the response capability of the nation’s public health laboratory system. The impressive response to the outbreak in Sheboygan testifies to the expertise and commitment of these laboratory professionals. It also epitomizes CDC’s World TB Day theme: “Find TB. Treat TB. Working together to eliminate TB.”