The learning never ends: Disease detectives follow every lead
By the fall of 2001, Daniel Jernigan, M.D., M.P.H., knew his way around respiratory disease investigations. As a seasoned epidemiologist, with the CDC since 1994, Jernigan liked the hunt—who was getting ill, was there a cluster of cases, what relationship did patients have with each other, how long were they ill, when did symptoms begin, what was the attack rate?
In 1994, as a new CDC Epidemic Intelligence Service (EIS) Officer, he helped successfully identify the source of infection for an outbreak of pneumonia. Cases of Legionnaires' disease had been popping up in adults along the East Coast.
"What made this outbreak investigation unusual was that it was a respiratory disease and, yet, we were able to trace it back to a point source. Typically respiratory outbreaks can't be traced back to an original point of infection—that's the type of experience you get with foodborne or waterborne investigations, not airborne," Jernigan explained.
Applying detection methods
Applying their epidemiologic detection methods, the public health investigators identified legionella in whirlpool spas on the cruise ship Horizon as the source. It turned out that the Legionnaires' disease cases occurred from nine separate week-long cruises to Bermuda. Exposure to whirlpool spas on the ship was the common thread among those who became ill compared with those who did not.
On Oct. 4, 2001, the first case of inhalation anthrax in the United States since 1976 was identified in a media company worker in Florida. Three days later Jernigan was leading the CDC's epidemiology team in Atlanta for this rare respiratory disease investigation. Once again, he was in the unusual position to investigate a respiratory disease outbreak that could ultimately be traced to a point source.
"Right away we needed to determine the source. This was complicated--we later found out--by the fact that two different sets of letters were mailed. We were using data collected by public health investigators as we tried to answer, who was affected, what were their characteristics, were they related to each other in some way? These questions were meant to help us identify interventions and stop additional disease transmission," he said.
The investigation expanded over the weeks as more cases were found. "This was an unprecedented outbreak investigation. It challenged us in the traditional sense of finding out how the disease organism was being transmitted and the volume of data analysis that was required, but also in sheer scope. We would 'birth' a new team for each new location where anthrax cases were found. We had CDC teams working with Florida, North Carolina, New York, New Jersey, and D.C. We also had a postal team. They were working with public health and other agency officials on the investigation response," he recalled.
Through the exhaustive weeks of that response, Jernigan and his colleagues, wittingly or not, were applying all that they knew about investigations using an outbreak model while their approach, by necessity, began to incorporate the incident command model of response. "We learned that the outbreak model must persist, but in extraordinary outbreaks, the incident command model is vital too. We needed greater situational awareness, beyond the scope of outbreak data collection. We needed better systems to communicate and interact with partners, elected officials, the media, and public," he said.
What he learned from a cruise ship outbreak he poured into the anthrax response. Next, Jernigan took everything he learned from the anthrax attack--and subsequent responses such as West Nile, SARS and Katrina-- into his role as the Epidemiology and Laboratory Team Lead for the H1N1 pandemic influenza response.
Absolutely critical to response
"What we learned from the anthrax response was absolutely critical to our pandemic response. Anthrax taught us the value of having laboratory processes in place, the need for rapid diagnostics, how to communicate uncertainty, and the importance of collaboration with others."
Jernigan is "paying it forward" as he continues to help refine public health emergency response. "It was validating to see how extremely well the pandemic response went. We had public health labs ready and trained. Diagnostic tests were created and the mechanisms and surge capacity were in place to distribute tests and reagents to all health departments and partner labs.
Value of consequence modeling
"We learned the value of regulatory preparedness. We must work with USDA and FDA to identify and manage regulatory obstacles that can come up in a response. We also learned the value of consequence modeling—a capacity we did not have during anthrax.
"Consequence modeling allows us to take many bits of information and analyze them to predict outcomes. Even with a range of expectations, we can use the information to drive interventions and help leadership make decisions. It allows us a level of confidence in the way we organize and make recommendations," he said.
After cruise ships, anthrax letters, and pandemic viruses, Jernigan, currently the Deputy Director of the CDC's Influenza Division, is still on the hunt. "The answers are out there if we know how to look for them. We are determined to intervene where we can and stop the spread of disease—that's public health."
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