Five African countries are battling outbreaks of anthrax, with nearly 1,200 people affected so far and 20 deaths, according to the World Health Organization. But the official tally belies confusion about the exact nature and scale of the outbreaks, which may complicate the efforts needed to contain them.
Of the 1,166 presumed anthrax cases in Kenya, Malawi, Uganda, Zambia and Zimbabwe, only 35 have been confirmed with lab tests. That is not unusual or unreasonable, experts said, especially in regions with limited resources.
But at least in Uganda, many of the presumed cases have resulted in negative tests for anthrax, raising the possibility that a second disease is circulating.
“It could simply be that the diagnostic testing is inadequate, or it could be that you have a moderate number of anthrax cases and simultaneously you have an outbreak of something else that could look similar,” said Dr. Andrew Pavia, an infectious disease expert at the University of Utah who has advised the Centers for Disease Control and Prevention on anthrax treatment guidelines.
Anthrax does not typically spread between people, so the outbreaks so far are thought to be confined to people who consumed meat from infected animals. Uganda has now banned the sale of beef products.
“Even if somebody with cutaneous anthrax got off a flight in Washington, D.C., they’re not going to infect anyone — as long as they don’t have a duffel bag full of contaminated meat that they pass around,” Dr. Pavia said.
Anthrax is caused by extraordinarily resilient bacteria called Bacillus anthracis that can survive in soil and water for decades or even centuries. Cattle become infected when they ingest spores in the soil while grazing, and they can fall ill and die just two or three days later.
Outbreaks in cattle are particularly likely after the type of heavy rains that eastern and southern African nations have recently experienced.
In humans, anthrax can cause skin ulcers with a black center and swelling, which can suffocate the patient if it extends to the chest.
Sporadic outbreaks of anthrax in wild animals, cattle and people are not uncommon in these countries. But having five outbreaks simultaneously “is probably a little odd, and that’s probably what’s generating some news attention,” said Dr. William Bower, an anthrax expert at the C.D.C.
In Uganda, the first suspicious cattle death was in June in Kyotera District, and the first sudden human death was reported in July, according to an internal report obtained by The New York Times.
By the end of October, at least 24 animals had died. Some infected animals and people have since popped up in Kalungu District, about 45 miles north of Kyotera.
But it was only in mid-October, after reports of a mystery disease among people, that district officials began testing skin lesions from those affected. The first two samples turned up negative for anthrax and for several other diseases.
As of Dec. 6, Uganda’s official tally stood at 48 presumed cases. But of the 11 for whom results were available, only three were positive for anthrax; the remaining eight tested negative, according Kyotera officials.
Still, that may not mean the patients are free of anthrax, said Dr. Jean Paul Gonzalez, an expert in hemorrhagic fevers at Georgetown University who has trained 250 Ugandan scientists on emerging infections.
Uganda’s lab facilities can reliably test for anthrax, but only if the samples are properly taken and processed, Dr. Gonzalez said.
Dr. Jean Kaseya, director general of Africa Centers for Disease Control and Prevention, said officials were relying on the patients’ symptoms, as well as on known links to diseased cattle or contaminated meat, to determine whether they had anthrax.
“Because we have confirmed cases, because we have these deaths confirmed due to anthrax, there is no doubt for us that this is anthrax,” Dr. Kaseya said.
The patients in Kyotera District had itchy lesions on the hands and arms, swelling and numbness of the affected limbs and headache. This was sometimes followed by swelling of the chest, difficulty in breathing and death.
“That sounds very much like anthrax,” Dr. Bower said.
While there is a vaccine for anthrax, Dr. Kaseya noted, it is not available in Africa, where the disease is a far greater problem. “This is inequity, and it’s not acceptable,” he said.
He added that Africa C.D.C. was working closely with Uganda’s ministry of health to help with the investigation. But officials in Kyotera face numerous hurdles in their attempts to identify and diagnose cases, according to the internal report.
“Suspected cases unwilling to show their skin lesions and allowing samples being taken,” the report said. Some people with symptoms have given officials incorrect information or refused to provide information at all.
Officials also lack enough cars and fuel to travel to affected areas and evacuate critically ill patients.
Convinced that witchcraft is to blame for the disease, many patients eschew clinics for traditional healers. That has led to at least one death at a shrine in Kalungu.
Paul Ssemigga, 68, a farmer, believes he fell ill after eating contaminated meat. He sought help from a traditional healer and took herbs for more than a month before he sought care at Kalisizo General Hospital in Kyotera.
It is unclear whether Mr. Ssemigga has anthrax. Of the eight patients treated at the hospital, test results are available for only two; both were negative for anthrax.
But so far, Mr. Ssemigga seems to be responding to antibiotics, and the swelling in his arms seems to be receding, said Dr. Emmanuel Ssekyeru, the hospital’s medical officer.
It is possible that those who tested negative for anthrax have cellulitis, a generic term for any deep skin infection, Dr. Ssekyeru said. Or they may have any of a number of diseases with similar symptoms: Rift Valley fever, a viral illness also seen in domesticated animals, for example, or infections with certain bacteria or with arboviruses like West Nile virus — or even tick bites.
Investigators should continue to consider these other possibilities, Dr. Pavia said.
“One rule in outbreaks is that you don’t close your mind off too early and you always consider that there’s a second pathogen or a second route of transmission,” he said.
Otherwise, officials may succumb to so-called confirmation bias, where “you have a few cases of one thing and so you try really hard to shoehorn others into that diagnosis, but you turn out to be wrong,” he said.