Source of Marburg Outbreak Sought
Wednesday, August 8, 2007; 4:05 PM
LONDON -- Virus hunters swathed in protective gear plan to enter a lead and gold mine in a remote part of western Uganda this week to search for bats they believe may be the source of the latest outbreak of a deadly Ebola-like disease.
Wearing gowns, boots, masks, goggles and leather gloves, the medical investigators will attempt to catch 1,000 bats to be transported to a nearby mobile laboratory, where they will take blood samples to look for antibodies of the Marburg virus, before killing the animals and removing their livers and spleens.
"It's quite dangerous work, but we hope it will help us answer some important questions about Marburg," Dr. Pierre Formenty, a hemorrhagic fever expert at the World Health Organization, said in a telephone interview Tuesday from Kampala, Uganda. "It will be a very delicate operation."
Last week, WHO confirmed one case of Marburg in a 29-year-old man who worked at the mine and who died on July 14.
Marburg is a rare and virulent disease for which there are no cures or effective treatments. It causes headaches, nausea, diarrhea and vomiting. In severe cases, the central nervous system is attacked, and patients may bleed from the eyes, ears and elsewhere.
Scientists are not sure how it is transmitted to humans, but believe people may become infected by being bitten by bats or by insects or other animals that have been infected by bats. Another possibility is that people catch it by breathing in air carrying virus particles from bat feces. Since Marburg was first identified in 1967, large outbreaks have been reported in Congo, Angola and other countries.
"If we knew what the animal reservoir was, we would have a better chance of stopping the infection," Formenty said, adding that experts could then more precisely warn people about which behaviors _ and animals _ were particularly risky. That "would open up new avenues for future treatments and developing vaccines."
Formenty and about two dozen other experts from WHO, the Centers for Disease Control and Prevention in Atlanta, Medecins Sans Frontieres, the Ugandan Ministry of Health and other agencies will be involved in the effort to collect bats from the mine.
The team may also take blood samples from miners and villagers in the area, to check for antibodies that would indicate they might have been exposed to Marburg. Experts think that sporadic cases of hemorrhagic fever in the region are not uncommon, and that cases of Marburg have probably gone undetected for years.
"We are learning new tricks from each outbreak," said Dr. Pierre Rollin, a Marburg expert from the CDC, who was on his way to Uganda on Tuesday. "If we cannot go to the outbreak site immediately after it happens, we are losing a chance."
Unlike previous Marburg outbreaks, when doctors have been preoccupied with trying to save peoples' lives, the number of patients in the current outbreak appears to be limited. In addition to the confirmed Marburg death, one other "highly probable" case is still alive, and health authorities are monitoring about 100 contacts of the two men, who both worked in the mine.
"In the past, the early teams that have gone out have been busy establishing isolation wards to prevent further infections and following up case contacts," said Dr. Stuart Nichol, a CDC Marburg expert.
By the time doctors were able to shift from treating patients to investigating the outbreak, many months had passed. "In this outbreak, we have a chance to focus on the ecological side soon after the outbreak to see where the disease may actually come from," Nichol said.
Some 5 million bats, as well other animals and insects, live in and around the mine at the center of the outbreak.
Bats have long been suspected of playing a role in transmitting Ebola and Marburg to humans. "There have been anecdotal reports in each outbreak that bats have been around," Rollin said.
After past Marburg outbreaks, scientists have trapped bats in surrounding caves and mines, but they have never found the smoking gun necessary to prove the bats' role in transmission: antibodies against the virus.
"Diseases like Marburg are very complex and take time to understand," Formenty said. "Every outbreak is an opportunity for us to prevent future infections."