Published Date: 2012-09-28 11:04:37
Subject: PRO/AH/EDR> Bas-Congo virus - Congo DR: (BC), viral hemorrhagic fever, 2009, RFI
Archive Number: 20120928.1314067
BAS-CONGO VIRUS - DEMOCRATIC REPUBLIC CONGO, VIRAL HEMORRHAGIC FEVER, 2009, REQUEST FOR INFORMATION
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 28 Sep 2012
Disease Detectives Catch Deadly African Virus Just As It Emerges
New viruses are popping up all over these days - Heartland virus in Missouri last month, a new virus in the same family as SARS in Saudi Arabia this month. And now, a never-before-seen hemorrhagic fever virus in central Africa.
It's called Bas-Congo virus after the province where it was found just west of Kinshasa, the teeming capital of the Democratic Republic of Congo. The discovery was announced today in the journal PLoS Pathogens.
So far only 3 people in the remote village of Mangala are known to have contracted Bas-Congo hemorrhagic fever, 2 of whom died. One was a health care worker who cared for the other 2 villagers, which means it can apparently be transmitted from person to person, although no one knows how easily.
But the small number of known cases is actually one of the important things about this finding.
It signifies that scientists may have found an emerging disease very soon after it made its jump from whatever species it came from into humans. We'll come back to its most likely origins a little later.
The reason for thinking Bas-Congo only recently began infecting humans is that researchers have run blood tests on people throughout the DRC and found no evidence of antibodies that would indicate any of them has been exposed to the new virus.
"It doesn't appear to be widespread throughout the Congo," study co-author Charles Chiu of the University of California San Francisco told Shots. He says the team is planning to do more blood tests on people in the DRC and neighboring countries, such as Congo-Brazzaville right next to Bas-Congo province.
"I would say we caught it fairly quickly," said another study author, Joseph Fair, in a telephone interview from the other side of the DRC, where he's helping to track down the origin of an ongoing outbreak of Ebola hemorrhagic fever that has so far afflicted 51 people and killed 20.
"This wasn't HIV, where we're 15 years into a pandemic before we actually find that we have a pandemic," says Fair, who's with a group called Metabiota that contracts with governments and health agencies to track disease outbreaks.
The 3 known cases of Bas-Congo fever actually occurred 3 years ago. But tissue samples from the victims languished in a laboratory freezer in Kinshasa until an astute doctor called the cases to Fair's attention.
That time lag, along with the inability to keep some tissue samples from thawing out, has hampered the researchers' ability to track the virus through other possible cases in Mangala village.
There are some other striking things about the new virus. It doesn't belong to any of the 4 families of previously known hemorrhagic viruses -- Arenaviridae, Bunyaviridae, Filoviridae and Flaviviridae. These families harbor such notorious bugs as Ebola, Marburg, Lassa fever, Crimean-Congo hemorrhagic fever, dengue fever and Rift Valley Fever.
Instead, Bas-Congo belongs to the Rhabdovirus family, which has never been known to include human hemorrhagic fever viruses, although it does contain one that affects fish.
"That in itself is astonishing," Chiu says, "but even within the rhabdovirus family, it's very divergent." That is, it doesn't resemble any other rhabdovirus.
And where did it come from? That's still a mystery, but one clue is that its closest relatives are insect viruses. So researchers are trapping mosquitoes, sandflies, ticks and other insects to see if they can find where Bas-Congo virus hangs out when it's not threatening humans.
The discovery of Bas-Congo is only the latest instance of a powerful new-ish technology that is proving crucial in the identification and characterization of new infectious organisms. It's called deep sequencing, and it allows scientists to spell out the millions of nucleotide sequences in any new microbe without reference to those of known pathogens.
Deep sequencing was also used recently to characterize the new coronavirus that has infected 2 men in Saudi Arabia [& Qatar].
Once scientists have their hands on the complete genome of these new organisms, they can place it on the right family tree relative to known microbes, providing crucial clues on where it may have come from and what species it likes to infect.
They can also, as in the case of the Saudi virus and Bas-Congo, make diagnostic tests to see who else has been infected. "By knowing the genetic identity, now we will add this to our battery of tests for hemorrhagic fever cases that come in," Fair says.
"Up to 20 percent of hemorrhagic fever outbreaks in the Congo don't have a diagnosis," Chiu says. "They test negative for Ebola, Marburg and everything else. So I suspect there are several other viruses out there that have yet to be discovered."
Fair is confident they will be found, thanks to new technologies - from rapid-throughput gene sequencing to solar power to run freezers. He foresees a new chapter in the detection of emerging diseases "right when they start."
"If we can detect it, we can stop it," Fair says. "That's a bold statement, but that's where we aim to be."
[Byline: Richard Knox]
Date: 28 Sep 2012
Source: PLos Pathogens
Grard G, Fair JN, Lee D, Slikas E, Steffen I, et al. (2012) A Novel Rhabdovirus Associated with Acute Hemorrhagic Fever in Central Africa. PLoS Pathog 8(9): e1002924. doi:10.1371/journal.ppat.1002924
Deep sequencing was used to discover a novel rhabdovirus (Bas-Congo virus, or BASV) associated with a 2009 outbreak of 3 human cases of acute hemorrhagic fever in Mangala village, Democratic Republic of Congo (DRC), Africa. The cases, presenting over a 3-week period, were characterized by abrupt disease onset, high fever, mucosal hemorrhage, and, in 2 patients, death within 3 days. BASV was detected in an acute serum sample from the lone survivor at a concentration of 1.09�--106 RNA copies/mL, and 98.2 percent of the genome was subsequently de novo assembled from [approximately] 140 million sequence reads. Phylogenetic analysis revealed that BASV is highly divergent and shares less than 34 percent amino acid identity with any other rhabdovirus. High convalescent neutralizing antibody titers of greater than 1:1000 were detected in the survivor and an asymptomatic nurse directly caring for him, both of whom were health care workers, suggesting the potential for human-to-human transmission of BASV. The natural animal reservoir host or arthropod vector and precise mode of transmission for the virus remain unclear. BASV is an emerging human pathogen associated with acute hemorrhagic fever in Africa.
[On 26 Jun 2009, there was a ProMED-mail post on an outbreak of apparent viral hemorrhagic fever in Mangala, Democratic Republic of the Congo. The newswire at that time mentioned the following: "5 people out of almost a dozen ill individuals have died within a few days from an as yet unidentified disease in the village of Mangala, located some 30 kilometers [19 mi] from the city of Boma, the capital of the province of Bas-Congo [Kongo Central] in the west of the Democratic Republic of the Congo (DRC).
"The chief medical officer of the Boma health district, Dr Lawrence Kiphunda Nlandu, who informed the press, reported that 5 cases, of which only one has survived so far, a man of 35 years, have been detected in the rural health zone of Boma Bungu, considered the epicenter of the epidemic, while the other 5 cases were recorded in the Boma health area. He mentioned that 2 men, a woman, and a young man of 14 years of age are currently hospitalized in a local medical facility and a child of 4 years who succumbed to the disease [referring to the 2nd cluster mentioned above].
"Dr Kiphunda did not provide the incubation period of the disease, however he mentioned that it is characterized by vomiting of blood [hematemesis] accompanied by bloody diarrhea [melena or hematochezia] and blood flow from the nostrils [epistaxis]." (see prior ProMED-mail post Undiagnosed fatalities - Congo DR: (BC), hem fever susp, RFI 20090626.2326 -- information at that time from a French language Xinhua newswire http://french.news.cn/afrique/2009-06/22/c_135184.htm).
At that time, this moderator mentioned: "The differential diagnosis for a hemorrhagic fever in the Democratic Republic of the Congo (DRC) would include more 'common' etiologies such as leptospirosis, yellow fever, malaria, Crimean-Congo hemorrhagic fever and dengue hemorrhagic fever, among others.
"The more 'exotic' viral hemorrhagic fevers such as Ebola, Lassa & Marburg, while they not been reported from the Bas Congo region of the DRC, have been reported from elsewhere in the DRC, and from neighboring Angola." (see prior post for more complete discussion on the epidemiology of the VHFs in the region)."
No further information was received at that time  to identify the etiology of the outbreak, and the report remained in the ProMED-mail archives as an as yet unresolved outbreak of a hemorrhagic fever.
The above reports put "closure" to the open investigation, 3 years following the event.
Of note, 3 days following the report of the outbreak in Bas-Congo (29 Jun 2009) , there was another report of an as yet undiagnosed outbreak of a hemorrhagic fever in Equateur Province of the DRC (see ProMED-mail Hemorrhagic fever - Congo DR: (Equateur), RFI 20090629.2357). That outbreak was described as: "Eight cases of haemorrhagic fever have been reported since May  in the Djolu health area. According to the provincial medical inspector of Equateur, 4 deaths have already been reported among persons under treatment, as reported by radio okapi.net.
"Patients have presented with the same signs: fever with bleeding from the nose (epistaxis) and anus (hematochezia) and vomiting with blood (hematemesis). But according to Dr Augustine Makaya, provincial medical inspector, the viral etiology of this disease is not yet known. Blood samples taken last Wednesday [?24 Jun 2009] on patients by a team from Medecins sans Frontieres [Doctors Without Borders] in Kisangani, were sent on the same day by plane to Kinshasa." (see prior ProMED-mail post Hemorrhagic fever - Congo DR: (Equateur), RFI 20090629.2357, with information from Radio Okapi via Relief Web http://www.reliefweb.int/rw/rwb.nsf/db900SID/JBRN-7TDDM9?OpenDocument).
At that time, this moderator mentioned: "In addition to the outbreak of Ebola hemorrhagic fever in 2008, Equateur Province has had outbreaks of Ebola hemorrhagic fever in 2007 (along the Tshuapa river) and in Yamabuku in 1976 (the Ebola river goes through Equateur Province. The Yambuku outbreak was the 1st outbreak of Ebola hemorrhagic fever identified, and at the time, Yambuku was situated in Equateur Province).
"Outbreaks of Marburg hemorrhagic fever have been identified in neighboring
Kasai Orientale Province as well." A search of the internet has not revealed an etiology for this 2nd hemorrhagic fever outbreak.
An obvious question at this time is whether those specimens sent to Kinshasa for processing have also [yielded] a new virus responsible for viral hemorrhagic fever? Or, perhaps the same virus as identified in Bas-Congo?
For maps of the Democratic Republic of the Congo, see http://www.mapsofworld.com/democratic-republic-of-congo/maps/democratic-republic-of-congo-political-map.jpg and http://healthmap.org/r/3yuF. - Mod.MPP]