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There are a number of viral diseases that can cause hemorrhage, but the ones that keep popping up in Uganda are Ebola, and Marburg virus diseases. Ebola and Marburg are related viruses, both of the same family (Filoviridae). They cause short-lived, intense illnesses, characterized by acute onset of high fever, chills, malaise, general prostration and high mortality. The symptoms largely reflect the storm of pro-inflammatory mediators released by the infected cells of the innate immune system (mostly macrophages) which spiral out of control, and can lead to the hemorrhagic manifestations which make the diseases both so scary, and so apt for use in hollywood films - basically, bleeding from every orifice.
The case fatality rates range from 21% -- if you contracted Marburg virus in Germany in a 1967 outbreak -- to 90% -- if you contracted Marburg virus in Angola in 2005. The case-fatality ranges for most of the relevant Ebola strains are similar - from 50-90% (with all outbreaks occurring within Africa). There is debate as to whether the wide mortality range documented for Marburg is attributable to strain characteristics, or the quality of available medical care at the outbreak sites - I suspect that it was at least in large part due to the latter.
While Ebola Virus takes its name from a river in what is now the Democratic Republic of the Congo (then Zaire), interestingly, Marburg Virus actually takes its name from Marburg, Germany. Marburg was the city where hemorrhagic fever made its Western debut when in 1967 an outbreak infected 25 individuals harvesting tissue to produce the poliovirus vaccine. They were harvesting tissue from -- you guessed it -- monkeys sent from Uganda. And while Germany has been lucky enough to avoid further outbreaks (probably because the Ugandan monkey tissue industry isn't what it used to be), central and East Africa have not been as lucky.
Most often, outbreaks occur when an index case comes in contact with an infected monkey. Monkeys are not thought to be the natural reservoir of the viruses, as they also become ill and often die from the disease. When encountered, though, weakened or dead monkeys often end up as food. In an outbreak in Gabon in 1996, a dead chimpanzee was butchered and eaten by 19 people, all of whom quickly became ill. There is also some evidence that fruit bats may be a reservoir for Marburg virus, as several European tourists developed the disease after separately visiting a particular (bat-ridden) cave in eastern Uganda (one of whom died). Most often, however, the index case does not live to tell the story of their exposure.
Generally, the disease spreads by direct contact with the bodily fluid of actively ill patients, or by iatrogenia. In one terrible outbreak in 1976, the index case presented to a small missionary health outpost in (then) Zaire. Because he presented with high fevers, he was treated with injectable quinine for severe malaria. The needle was then washed in a pan of water with the other needles with which they routinely injected all febrile patients with anti-malarials. Almost 100 patients were infected and died. It is also possible that the 2006 Marburg outbreak in Angola was caused by inappropriately reused blood bank equipment.
Generally, however, infection only occurs with direct contact with bodily fluids, either during illness, or during the common (sometimes religious) custom of washing the body of the deceased before burial. There is no evidence of infection being acquired from asymptomatic patients during the incubation period. There has also never been clear evidence of airborne transmission in previous outbreaks (despite what Dustin Hoffman says). There was, however, one episode in 1996 in which a patient presented to a hospital in Zaire with abdominal pain, and underwent exploratory laparotomy. There wasn't much to find in the abdomen, but they did manage to aerosolize some blood, thereby infecting the entire OR staff and subsequently their families and caretakers when they became ill. There was also a recent article purportedly documenting airborne transmission in laboratory conditions between pigs (another potential reservoir) and monkeys.
Perhaps the most unexpected tidbit I found about transmissibility was that, in fact, Ebola and Marburg are also potentially sexually transmitted diseases. There has been well documented viral persistence in (amongst other places) the semen of surviving men for up to 3 months after infection, and following the 1967 outbreak in Marburg, there was one documented sexual transmission from a survivor. Oops! So I guess the lesson is this: pity sex with a cancer patient - OK; pity sex with a hemorrhagic fever survivor - best wait on that.
So what's happening here in Uganda?
The first outbreak this year was an Ebola outbreak, occurring in Kabaale (a southwestern area of Uganda). It was announced on July 29th, and the last confirmed case was discharged from the hospital on August 24th, though the outbreak was not officially declared over until October 4th (observing a pre-determined observation period that is about twice the maximum incubation period). There were 24 confirmed and suspected cases (only a portion of which had confirmatory viral testing performed), including 16 deaths. The majority of deaths, as in most outbreaks, were amongst the family of the index case.
Shortly thereafter, Uganda also suffered an outbreak of Marburg Virus this year. The outbreak began in October, and was declared over in late November (days before the most recent outbreak), and ultimately included 20 probable or confirmed cases, and 9 deaths which were spread across 4 districts (Kabaale, Ibanda, Mbarara, and Kampala). The index case was a school teacher, and it is unclear what his exposure might have been. Both he and later his infected caretakers travelled by bus around central and southwestern Uganda, including through the busy capital here, mostly to assist in the care of sick family members (who initially, at least, were sick with something other than Marburg).
The most recent, and not yet officially concluded outbreak of Ebola began in Luweero, a small city about 40 miles north Kampala. The index case was a Boda Boda driver, with an unknown exposure, who died on October 25th, having been taken care of in the village by his family and never having visited a health center. The next two deaths occurred on November 10 and 12th, were both family members and caretakers of the index case, and died at the local health center, thereby increasing the number of exposed individuals. As of now, there have been 7 confirmed and suspected cases, with 5 deaths.
If nothing else, the string of recent outbreaks ensured that the infrastructure necessary to respond to the most recent outbreak was in place. There were pre-existing isolation facilities at several hospitals (including Mulago Hospital, here in Kampala), and international expertise (from the likes of the CDC, MSF, etc.) to help coordinate a response. The most recent outbreak was quickly contained, and really limited to family members of the index case and their immediate caretakers. Outbreak control is done primarily by 1) isolation of known or suspected patients, and 2) contact tracing for known contacts of patients. Essentially, if you had contact with a case but are asymptomatic, someone checks up on you every day. If you develop any symptoms, you're off to isolation.
But I expect that the question on everyone's mind is - what is it like being here during an outbreak? Well, I'm sorry to disappoint, but the answer is - it's the same as before. Although these are scary diseases, the rapidity of the initial response ensured that Ebola patients were not showing up on the wards at Mulago hospital. I think there were 2 suspicious cases seen in the Emergency Department, who were quickly rushed to isolation, though they both ultimately they received alternative diagnoses. As such, during this outbreak, the only Ebola patients at Mulago hospital were known contacts who were taken directly to the separate isolation area (located in a cluster of tents set up in a fenced off area behind the hospital). So I cannot feign bravery or altruism in deciding to stay here - it just didn't come up. If there had been Ebola cases popping up on the wards, that would have been a different story.
As one of the senior physicians here put it, Ebola is not a "smart disease." If you want to be successful, be indolent - like HIV - infect millions before we know what happened. But if you just go and kill your host in a few fever-ridden days!? You won't make it very far.
Luckily, this outbreak hasn't made it very far. Here's hoping it stays that way.
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| 180 degree panorama of Murchison Falls - of The African Queen fame, Northwest Uganda |
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