Mystery amid an anthrax outbreak in Africa
According to the World Health Organization, five African countries are experiencing outbreaks of anthrax, which have so far affected nearly 1,200 people and killed 20 people. But the official count belies confusion over the exact nature and size of the outbreaks, which could complicate efforts needed to contain them.
Of the 1,166 suspected cases of anthrax in Kenya, Malawi, Uganda, Zambia and Zimbabwe, only 35 have been confirmed by laboratory testing. That’s not unusual or unreasonable, experts say, especially in regions with limited resources.
But in Uganda at least, many of the suspected cases have resulted in negative tests 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 at the same time you have an outbreak of something else that could look the same,” says Dr. Andrew Pavia, an infectious disease expert. at the University of Utah, who advised the Centers for Disease Control and Prevention on guidelines for treating anthrax.
Anthrax does not typically spread among humans, so outbreaks so far are believed to have been limited to people consuming meat from infected animals. Uganda has that now banned the sale of beef products.
“Even if someone with skin anthrax gets off a flight in Washington, D.C., he’s not going to infect anyone — as long as he doesn’t have a duffel bag full of contaminated meat that he’s passing around,” said Dr. Pavia. .
Anthrax is caused by extremely resilient bacteria called Bacillus anthracis, which 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 become sick and die just two or three days later.
Outbreaks among livestock are especially likely after the kind of heavy rains that countries in eastern and southern Africa 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 wildlife, livestock and humans are not uncommon in these countries. But having five outbreaks at the same time “is probably a little strange, and that’s probably what’s generating the news attention,” said Dr. William Bower, an anthrax expert at the CDC.
In Uganda, the first suspicious livestock death occurred 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. Since then, some infected animals and people have emerged in Kalungu district, about 72 kilometers north of Kyotera.
But it wasn’t until mid-October, after reports of a mysterious illness among people, that district officials began testing skin lesions of those affected. The first two samples were negative for anthrax and several other diseases.
As of December 6, Uganda’s official count was 48 suspected cases. But of the eleven for whom results were available, only three were positive for anthrax; the remaining eight tested negative, according to Kyotera officials.
Still, that may not mean the patients are free of anthrax, says Dr. Jean Paul Gonzalez, an expert on hemorrhagic fever at Georgetown University who has trained 250 Ugandan scientists on emerging infections.
Ugandan laboratory facilities can reliably test for anthrax, but only if the samples are collected and processed properly, said Dr. Gonzalez.
Dr. Jean Kaseya, director general of the Africa Centers for Disease Control and Prevention, said officials relied on the 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 confirmed these deaths from anthrax, there is no doubt in our minds that this is anthrax,” said Dr. Kaseya.
The patients in Kyotera district had itchy lesions on the hands and arms, swelling and numbness of the affected limbs, and headaches. This was sometimes followed by swelling of the chest, difficulty breathing and death.
“That sounds a lot like anthrax,” said Dr. Bower.
Although a vaccine against anthrax exists, Dr. Kaseya, this is not available in Africa, where the disease is a much bigger problem. “This is inequality and unacceptable,” he said.
He added that Africa CDC was working closely with the Ugandan Ministry of Health to assist in the investigation. But officials in Kyotera face numerous hurdles in their efforts to identify and diagnose cases, according to the internal report.
“Suspected cases who do not want to show their skin lesions and allow samples to be taken,” the report said. Some people with symptoms have given officials incorrect information or refused to provide information at all.
Officials also do not have enough cars and fuel to travel to affected areas and evacuate seriously ill patients.
Convinced that witchcraft is the cause of the disease, many patients avoid clinics for traditional healers. That has led to at least one death at a shrine in Kalungu.
Paul Ssemigga, 68, a farmer, believes he became ill after eating contaminated meat. He sought help from a traditional healer and used herbs for over a month before seeking help at Kalisizo General Hospital in Kyotera.
It is unclear whether Mr Ssemigga has anthrax. Of the eight patients treated in the hospital, test results are available for only two patients; both were 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, the hospital’s medical officer.
It’s possible that those who tested negative for anthrax have cellulitis, a general term for any deep skin infection, said Dr. Ssekyeru. Or they may have one of a number of diseases with similar symptoms: Rift Valley fever, a viral disease that also occurs in domesticated animals, for example, or infections with certain bacteria or with arboviruses such as West Nile virus – or even tick bites.
Researchers should continue to consider these other possibilities, said Dr. Pavia.
“One rule in outbreaks is not to close your mind too early and always remember that there is 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 get others to that diagnosis, but you turn out to be wrong,” he said.