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Hunting Down the Source of the Deadly Marburg Virus

In In the summer of 2007, a team of CDC researchers entered a dark, hot mine in western Uganda, searching for something more valuable than precious metal. Forty years had passed since the first reported outbreak of the deadly Marburg virus in a German laboratory. Now, a world away, they were tracking down the source of one of the most deadly pathogens known to man. When two miners fell ill at the Kitaka mine in Uganda from Marburg hemorrhagic fever in early August 2007, CDC staff quickly contained the outbreak and acted on a rare opportunity to trace the outbreak to its source.

“The public health response is first and foremost,” says Jonathan Towner, PhD, a microbiologist with CDC. “But because the outbreak was limited, it allowed us to very quickly mount an ecological study where we could look for the Marburg virus reservoir.”

By choosing to limit the focus of the investigation to the mine, the pool of potential natural hosts was narrowed to the bat species inhabiting the mine, two of which were already familiar to the CDC team: a small, insectivorous bat, and a larger fruit bat.

Earlier that year, the CDC team, with scientists from Gabon, had conducted an ecological investigation that showed evidence of Marburg virus infection in the fruit bat. This was the first study to definitively document evidence of the virus in wild nonprimates. It was also the first study to document evidence of Marburg virus in the Central African country of Gabon. The Ugandan mine provided a timely opportunity to continue the research efforts.

Wearing full safety gear—masks, gloves, boots and gowns—the research team and collaborating South African scientists entered the Kitaka mine hoping to build upon the results from Gabon. At the mouth of the cave, the team set up nets that trapped the bats as they left the cave at night to forage for food. Thus began a nightly ritual that lasted for nearly three weeks. The bats caught in the traps were taken back to a lab for analysis.

By the time the CDC team left in early September, they had collected more than 1,000 bats and assisted the Ugandan Ministry of Health in tracing every known contact of the infected miners through the 21-day incubation period to ensure that the outbreak had been contained.

“The discovery of Marburg virus infection in fruit bats in Gabon helped guide our investigation in Uganda,” said Towner. “We are still in the process of testing all of the bats that were trapped at the Ugandan mine. If infected bats are found in this collection, we could be a little closer to learning how the bats might have transmitted the Marburg virus to the miners.” Discovering the mode of transmission could assist with implementing risk reduction measures and aid CDC’s goal to protect Americans at home and abroad from health threats through a transnational prevention, detection and response network.

Marburg virus is a member of the same family of viruses as Ebola, i.e., Filoviridae. It was first recognized in 1967, after outbreaks of hemorrhagic fever occurred in laboratories in Marburg (hence the name) and Frankfurt, Germany, and in Belgrade, Yugoslavia (now Serbia). Marburg causes a severe and often fatal illness in humans and nonhuman primates. There is no vaccine to prevent the disease and no specific treatment. Humans become infected with Marburg virus by direct contact with blood or body fluids or with objects contaminated with body fluids from an infected animal or human. Reports of this disease are rare, but there have been recent occurrences in countries in sub-Saharan Africa.