Dr. Ross Donaldson recalls traveling around the Sierra Leone city of Kenema a decade ago, "telling people not to eat rats."
The multimammate rat, which is ubiquitous in sub-Saharan Africa, can carry a deadly hemorrhagic illness akin to Ebola, known as Lassa fever. Yet for many residents of the impoverished region, the animal remains a staple food.
"From a foreign perspective, it seems like a no-brainer," said Donaldson, who spent the summer of 2003 at Kenema Government Hospital's Lassa ward as a medical student studying the virus and treating its victims. He now directs the Emergency Medicine Global Health Program at the Harbor-UCLA Medical Center in Los Angeles County. "But when I was there, I could see a lot of things factoring in: the poverty, the lack of protein in the diet."
The scenario may sound eerily familiar. The hunting of primates and bats for food has been identified as a possible source of the current Ebola outbreak, which has claimed at least 5,000 lives in West Africa. While the cause is not proven, the outbreak's first victim, a 2-year-old child, may have been exposed to the virus while handling or eating an Ebola-infected bat.
Now Lassa fever too is threatening in those countries hard hit by Ebola -- Sierra Leone, Liberia and Guinea -- and other parts of the region.
Every year around mid-November, as the rains taper off and the dry season begins in West Africa, cases of the hemorrhagic fever generally ramp up. Nigeria reportedly began seeing its first Lassa outbreak of the season in October, only about a week after successfully containing Ebola. Estimates of Lassa fever's impacts in West Africa vary widely. Annually, anywhere from 100,000 to nearly 13 million people are infected, and between 5,000 and 67,000 die from the disease.
Experts warn that greater Lassa outbreaks across the region could be one of many ripple effects triggered by Ebola's re-emergence. With a severely strained health system scrambling to treat Ebola victims, care for and containment of Lassa patients may be limited. Other people may miss out on the medical care they need for prevalent infections such as malaria, HIV/AIDS and tuberculosis, or even for common complications during childbirth. Sierra Leone already has one of the highest maternal mortality rates in the world.
None of these sicknesses or deaths are counted in the official Ebola statistics.
"The Ebola outbreak itself probably pales in comparison to the true burden of disease from all the other illnesses worsened by the breakdown of the health care system," said Donaldson, who wrote a book chronicling his experiences, The Lassa Ward: One Man's Fight Against One of the World's Deadliest Diseases.
Unlike Ebola, treatment does exist for Lassa fever. However, it is usually effective only if administered early in the course of the disease -- at a time when Lassa's fever and vomiting can be easily confused with other conditions, including malaria, typhoid fever and Ebola. Consequently, some Lassa patients may be misdiagnosed, go untreated or even be exposed to one of those other diseases if admitted to a wrong ward. Adding to the challenge, fears of catching Ebola at a hospital are now keeping some people suffering symptoms from seeking treatment. In other cases, the help is simply not available. A number of doctors and nurses, including several Lassa specialists, have died in recent months from Ebola and malaria. Many more have walked off the job out of fear or are simply overburdened by Ebola patients.
In fact, when the current Ebola outbreak began, Kenema's Lassa ward was quickly repurposed to isolate and treat Ebola victims.
"Now, [they] don't have any place to put the Lassa patients," said Lina Moses, a Lassa researcher with Tulane University's Viral Hemorrhagic Fever Consortium. She flew from New Orleans to Sierra Leone over the weekend as part of an international effort, she said, to get Lassa incident surveillance and patient care "back up and running."
No one is sure, Moses said, why only West Africa is affected by Lassa fever despite the multimammate rat's pervasiveness elsewhere in Africa. And some fear the disease could spread.
Thierry Wirth, a professor at the Museum National d'Histoire Naturelle in Paris, told The Huffington Post of his concern that "scared emigrants" may attempt to escape the Ebola belt to countries not yet affected by either Ebola or Lassa. They could potentially carry one or both diseases with them.
He also agreed with other experts that the Ebola outbreak could heighten the risk of Lassa outbreaks where the latter disease is already endemic. Wirth co-authored a study in 2012 that concluded the Sierra Leone civil war -- which ended around the time Donaldson arrived in that country -- had probably amplified Lassa fever's spread by decimating the land and altering the movement of people and rats. Not all animals handle habitat disruption the same way. Compared to other creatures, the multimammate rat appears better able to adapt and thrive in a range of natural and human habitats, even as it carries and transmits a disease like Lassa.
Similarly, increased poverty as a result of the Ebola outbreak, said Wirth, could force people into more rudimentary lifestyles and more contact with these opportunistic rodents. Greater hunger might even drive more people to be "tempted by bushmeat," he said.
On the flip side, the attention Ebola has brought to the potential dangers of hunting local wildlife could also discourage the consumption of rats. "There are a tremendous amount of people terrified of eating bushmeat right now," said Moses.
But even if people avoid eating the rats, they can still be exposed to the Lassa virus. As the animal burrows into the common mud-and-stick homes, scurries under beds and scavenges for scraps of food, it leaves behind infected urine and feces.
With good reason, the global health community remains focused primarily on containing the Ebola outbreak and aiding those affected. But what will happen once Ebola does finally dissipate? Will world health officials turn to helping West Africa develop capacity to tackle the host of other illnesses plaguing its people? Will researchers seek greater understanding of the economic, cultural and environmental drivers of emerging infectious diseases, in an effort to prevent their spread the next time around?
Tara Smith, an infectious disease researcher at Kent State University in Ohio, is not optimistic. "I think we're going to see the same thing we see most of the time with epidemics in Africa," she said. "We get this short-term influx of supplies and good will and physicians, but then it gets ignored again."
Lassa fever is one of the "prototypical neglected diseases," said Donaldson.
"We could have vaccines or other interventions, but these things don't actually get made because there is not a perceived large market to make money," he said. "Much could be potentially done with a little bit of resource."
"I hope one of the benefits of this very tragic situation with Ebola," Donaldson added, "is that both Lassa fever and the health care system in West Africa get some longer-term help."