EDINBURG — Through brick wall after brick wall, Gloria Salinas and her staff kept searching for Patient Zero.
In cracking a tuberculosis outbreak that most health professionals thought impossible to solve, Salinas proved that a diagnostic practice previously confined to the laboratory setting could be applied in the time-intensive investigations that are her clinic’s forte.
Salinas, the TB program manager for the Hidalgo County Health and Human Services Department, has spent the last 14 years handling TB prevention and treatment in a county notorious for its massive tuberculosis investigations. She’s worked TB outbreaks in households, workplaces or in schools, where the legwork usually involves testing anywhere from 30 to 200 of the patient’s “contacts” for TB.
The paperwork detailing a single tuberculosis case is enough to fill a filing cabinet drawer.
Patient confidentiality prevents Salinas from discussing specific details of the 10-month investigation.
But she said her pulmonary clinic honed the use of a genotyping database in a way that hadn’t been done before in the state. The genotyping database catalogs specific strains of the TB bacteria and identifies the patients who contracted each strain.
In essence, Salinas showed that public health officials could trace a specific tuberculosis outbreak back to its source using a nationwide database of TB specimens. It’s an approach similar to law enforcement’s groundbreaking use of DNA to solve crimes.
“(The investigation) took quite a bit of time, manpower and brainstorming when we hit a lot of brick walls. But we used the genotyping to help find the initial culprit,” said Salinas, who will present the techniques she used to crack the case at a Centers for Disease Control and Prevention meeting next month. “Finding the source helped save a lot of people’s lives because we found out what type of TB germ it was and what appropriate medication we needed to give the other contacts.”
CRACKING A CASE
The 16 employees who work in Hidalgo County’s pulmonary clinic worked an average of 80 confirmed tuberculosis cases in each of the past six years.
On its face, the clinic’s caseload appears light. But a single TB case can involve hundreds of hours of legwork in treating a patient and preventing the spread of tuberculosis, a disease caused by bacteria that are spread through the air from one person to another by coughing, sneezing or talking.
To fight the spread of TB, public health departments adopt two basic techniques:
>> direct observation of TB patients for six to nine months to ensure they complete their medication;
>> and contact investigations to determine whether the disease spread to family members, coworkers or others in close contact with the patient.
Dr. Brian Smith, the director for the Texas Department of State Health Services region that oversees the Rio Grande Valley, said ensuring that treatment is completed prevents the development of drug-resistant TB, which increases treatment costs from an average of about $15,000 a case to nearly $250,000.
But public health workers also are confronted with the task of testing people who came in contact with the patient. It’s a task complicated by the stigma of the disease and by the sheer numbers of potential contacts; Hidalgo County once had 700 in a single outbreak.
But Smith said contact investigations are critical to curbing the spread of TB.
“It may be difficult to trace it to someone else because that connection may be distant. Very commonly, you have TB contacts that the patient hasn’t identified,” he said. “It’s every bit as much of an investigation as an FBI investigation.”
WORKING BACKWARD
The investigations are sometimes an open-and-shut case.
A person with TB symptoms is directed to the clinic, where they’re put on a series of medications and their contacts vetted for the disease. But what happens if you don’t know the source — the Patient Zero? That’s the quandary that confronted Salinas last year when, rather than working an investigation outward from the source, she had to work backward to find the source and prevent further spread of the disease.
In a case that initially puzzled public health officials, a group of Hidalgo County residents were testing positive through a skin test for a latent, or dormant, TB infection. Although patients with latent TB don’t show symptoms of the disease, about 5 percent to 10 percent of those people eventually develop the active form if they aren’t put on preventive medications.
But the best way to determine what cocktail of medications to give the person — especially if they have extensively drug-resistant TB — is to trace their infection back to the source.
The state established procedures nine months ago to genotype the strains of the TB bacterium to determine the appropriate treatment method and trace the source of an outbreak, said Charles Wallace, the manager of the tuberculosis services branch for the Texas Department of State Health Services. Because the same strain of TB produces matching genotypes regardless of whom it infects, samples from two or more TB patients with the same genotypes proves they got the disease from each other.
That comes in handy in situations where TB patients are unwilling or unable to name all the people and places for potential contact. Universal genotyping will allow the state to quickly link even obscure connections between patients to identify other potential patients and get them treated as well.
He said genotyping could help identify connections between a Webb County case and an Hidalgo County case, for example, allowing case workers to more deftly identify missing links and ensure no one else is infected.
“The link for us is always the contact investigation. We need the patient to be forthcoming about their contacts,” Wallace said. “It takes a lot of skill and finesse to get people to talk about their TB.”
CLOSING THE LOOP
Those are skills the pulmonary clinic’s staff has developed over years of working TB cases in a hotbed like Hidalgo County, said Eddie Olivarez, health and human services director. Although he couldn’t discuss the case specifically, he said Salinas and her staff merged old-school techniques — like interviews with patients — with new-school techniques — like genotyping — to pinpoint the origin of the TB outbreak.
“There was not a leaf that was not turned over to track this particular Patient Zero,” said Olivarez, who joined county commissioners in presenting Salinas with a plaque in recognition of her clinic’s work. “It was just her tenaciousness in solving a tough case.”
Salinas said her investigation showed that the database of genotypes could be used as a tool in a conventional contact investigation when no one knows the source of a TB outbreak. Salinas, who used genotyping to find Patient Zero and determine his or her connection with the rest, said finding the source without access to genotyping would have been about as easy as finding a needle in a haystack.
But she said she was determined to track the source until she reached a positive outcome.
“Finding the source can save lives,” she said.
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Jared Janes covers Hidalgo County government, Edinburg and general assignments for The Monitor. He can be reached at (956) 683-4424.
Website: www.themonitor.com/articles/edinburg-47121-investigative-program.html