Five African countries are battling anthrax outbreaks, with nearly 1,200 people affected so far and 20 deaths, according to the World Health Organization. But the official count belies confusion about the exact nature and scale of the outbreaks, which may complicate efforts needed to contain them.
Of the 1,166 suspected anthrax cases in Kenya, Malawi, Uganda, Zambia and Zimbabwe, only 35 have been confirmed by laboratory tests. This is neither unusual nor unreasonable, experts said, especially in regions with limited resources.
But at least in Uganda, many of the suspected cases have tested negative for anthrax, raising the possibility that a second disease is circulating.
“It could simply be that the diagnostic tests are inadequate, or it could be that you have a moderate number of anthrax cases and simultaneously have an outbreak of something that might 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 usually spread between people, so outbreaks are so far thought to be limited to people who ate meat from infected animals. Uganda has now banned the sale of meat products.
“Even if someone with cutaneous anthrax got off a flight in Washington, D.C., they won't infect anyone as long as they don't have a duffel bag full of contaminated meat passed around,” Dr. Pavia said. .
Anthrax is caused by an extraordinarily hardy bacteria called Bacillus anthracis that can survive in soil and water for decades or even centuries. Cattle become infected when they ingest spores from the ground while grazing, and can become ill and die just two or three days later.
Outbreaks in livestock 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 spreads to the chest.
Sporadic outbreaks of anthrax in wild animals, livestock, and people are not uncommon in these countries. But having five outbreaks simultaneously “is probably a little strange, and that's probably what's generating some media attention,” said Dr. William Bower, an anthrax expert at the CDC.
In Uganda, the first suspected livestock death occurred in June in the 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. Since then, some infected animals and people have turned up in the Kalungu district, about 45 miles north of Kyotera.
But it was not until mid-October, after reports of a mysterious illness among people, that district officials began examining the skin lesions of those affected. The first two samples tested negative for anthrax and several other diseases.
As of December 6, Uganda's official count stood at 48 suspected cases. But of the 11 whose results were available, only three tested positive for anthrax; the remaining eight tested negative, according to Kyotera officials.
Still, that may not mean patients are free of anthrax, said Dr. Jean Paul Gonzalez, a Georgetown University hemorrhagic fevers expert who has trained 250 Ugandan scientists on emerging infections.
Ugandan laboratory facilities can perform reliable anthrax testing, but only if samples are collected and processed properly, Dr. Gonzalez said.
Dr. Jean Kaseya, director-general of the Africa Centers for Disease Control and Prevention, said officials were relying on patients' symptoms, as well as known links to sick livestock or contaminated meat, to determine whether they had anthrax. .
“Because we have confirmed cases, because we have these confirmed deaths due to anthrax, we have no doubt that it is anthrax,” Dr. Kaseya said.
Patients in Kyotera district had itchy lesions on their hands and arms, swelling and numbness of the affected limbs, and headaches. Sometimes this was followed by swelling of the chest, difficulty breathing, and death.
“That sounds a lot like anthrax,” Dr. Bower said.
While there is a vaccine against anthrax, Dr. Kaseya noted, it is not available in Africa, where the disease is a much bigger problem. “This is inequity and it is not acceptable,” he said.
He added that Africa CDC was working closely with the Ugandan Ministry of Health to assist with the investigation. But Kyotera officials face numerous obstacles in their attempts to identify and diagnose cases, according to the internal report.
“Suspected cases do not want to show their skin lesions and allow samples to be taken,” the report says. Some people with symptoms have given officials incorrect information or have refused to provide any information.
Officials also lack enough cars and fuel to travel to affected areas and evacuate critical patients.
Convinced that witchcraft is to blame for the illness, many patients avoid clinics to go to traditional healers. This has led to at least one death at a Kalungu shrine.
Paul Ssemigga, a 68-year-old 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 seeking care at Kalisizo General Hospital in Kyotera.
It is not clear whether Mr Ssemigga has anthrax. Of the eight patients treated at the hospital, test results are available for only two; both tested negative for anthrax.
But so far, Mr. Ssemigga appears to be responding to antibiotics and the swelling in his arms appears to be going down, said Dr. Emmanuel Ssekyeru, a doctor at the hospital.
Those who tested negative for anthrax may have cellulitis, a generic term for any deep skin infection, Dr. Ssekyeru said. Or they may have a number of diseases with similar symptoms: Rift Valley fever, a viral disease also seen in domestic animals, for example, or infections with certain bacteria or with arboviruses such as West Nile virus, or even bites from ticks.
Researchers should continue to consider these other possibilities, Dr. Pavia said.
“A rule in outbreaks is not to close your mind too early and always consider that there is a second pathogen or a second route of transmission,” he said.
Otherwise, officials can succumb to so-called confirmation bias, where “you have a few cases of one thing and then you try really hard to cram others into that diagnosis, but it turns out you're wrong,” he said.
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