Disease Detective

Flying to an impoverished African country on your second day of work to battle a disease epidemic isn't most people's idea of a dream assignment. But it was for Marta Guerra. In fact, it was the assignment she had been coveting – and the virus causing the outbreak made it even better: Ebola.

One of the most frightening viral discoveries of the 20th century, Ebola attacks almost every tissue and organ in the body. Within a week, the victim begins to bleed from every body opening, including the eyes. There is internal hemorrhaging, shock, and often blindness. Death usually comes within two weeks.

"I wasn't that worried," Guerra says characteristically. "This particular strain has only a 65% death rate instead of the Congo strain which is 85%." To someone like Guerra, 44, that is a meaningful distinction. Guerra is a "disease detective" or Epidemic Intelligence Service (EIS) Officer for the Centers for Disease Control and Prevention (CDC), in Atlanta, Georgia. She is a member of a select group of medical professionals who have investigated some of the most virulent known viruses: polio, smallpox, cholera, AIDS, West Nile virus, bubonic plague.

Onsite at the Outbreak

Guerra was a practicing veterinarian for over 20 years before becoming a CDC detective. Local zoos, SPCAs, and other organizations often called her for information about zoonotic diseases, or animal diseases that jump the species barrier and infect humans. She found that she enjoyed teaching people about health risks and decided to go into public health. "I made the decision to go into public health because I felt that I wasn't reaching enough people on a case-by-case basis," she recalls. "I wanted to do more."

With the intention of working as an epidemiologist, Guerra then obtained a Master's in public health and a PhD in tropical medicine. She had always been interested in other cultures. She had studied anthropology as an undergraduate and was fascinated by stories that her professors told about working overseas. But it never occurred to Guerra that her studies in epidemiology could lead to international work.

Then, she saw the movie Outbreak. "I thought, that's what I want to do – help contain a deadly epidemic," recalls Guerra. "But I figured that was largely a fantasy …." Little did Guerra know when she entered the two-year EIS program that she would eventually go to Uganda to help contain Ebola, the very disease that was the subject of the movie.

The tasks of CDC detectives vary from situation to situation. When Guerra flew to Uganda in November 2000, the type of outbreak had already been identified, so her task was to educate the public to prevent further contagion. She acted as a liaison between various government and relief agencies to compile a database tracking the disease. She went from village to village, trying to locate family members and friends and educate them about symptoms and treatment. She also assured villagers that survivors, who often return to their villages to find their homes and possessions burned, should not be shunned.

"In every corner of Africa people know the word Ebola, and they are terrified of it," Guerra explains. "Sometimes they hide sick family members, sometimes they're frightened of survivors. We were lucky because families were receptive to our help."

On the Home Front

State health agencies and foreign countries call upon the CDC, when they need help with a medical situation that might become a public health threat. The CDC then dispatches a detective.

And that is what happened when, on her return from Uganda, Guerra was sent to Wyoming. With a team from the US Department of Agriculture and the state health department, Guerra helped determine that a farmer had contracted a case of Q fever from a goat he had purchased in Texas. Once they had made the diagnosis, the team tracked down anyone who had come into contact with the goat and/or the farmer and arranged for treatment.

Q fever is a disease that normally affects only goats and sheep. In humans, it can cause pneumonia and liver damage, which, in turn, may lead to death. Its main threat, however, relates to the fact that, once it is airborne, it can be used as a bioterrorist weapon. "Q fever is carried in an animal's placenta," Guerra explains. "Many animals give birth in the wild. Theoretically, if the placenta was outdoors, it could dry up and spores of the fever could pass through the air. Any aerosol virus is considered a bioterrorist threat because of its potential to sicken many people."

Not Deterred by Danger

Guerra seldom considers that she might acquire a disease she is investigating. Extensive precautions are taken in all CDC labs. The bigger danger is from the threat of political violence in third-world countries, where outbreaks often occur. In Uganda, Guerra's team adhered to a strict curfew and, because of possible rebel attacks, needed military escorts on their travels through villages. But that paled next to her experience in Ethiopia, in the summer of 2001, while on a polio-eradication mission. "We were in an open Land Rover on roads that barely existed," Guerra says. "There was rebel activity in all the areas we traveled through – plus land mines. It was pretty scary."

When Guerra tells people about her work, they frequently respond with apprehension, disbelief, and fear of what they perceive as the dangers of working with transmitted diseases. Guerra cannot explain why she does not share their fears, but the fact that she doesn't is what convinces her that she is in the right line of work. "Since not many people are willing to do it and I am, I feel that I have to."

Aside from potential risks, the life of a CDC detective is hectic and the work demanding. "You have to be highly motivated, with the ability to think fast on your feet and make quick decisions. You have to be able to walk into a chaotic situation and deal with whatever is thrown at you – including the media," Guerra says of the job. "Sometimes I barely drop my bags at home before I'm called out again. Being adaptable is really essential."

At the same time, the work is hugely gratifying. "Even little things [that we do] have a big impact," Guerra says. "I like the fact that I am contributing to science in the sense that what I do will affect people far into the future."

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