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Large numbers of people in Gabon have antibodies to Ebola

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  • Large numbers of people in Gabon have antibodies to Ebola

    Hat-tip Ironorehopper.



    9/2/2010 21.15


    Medicine and Health, Brief

    One part "surprisingly" high population of Gabon would be immune from the Ebola virus, responsible for one of the most severe forms of hemorrhagic fever currently known: according to a study published in the latest issue of the scientific journal 'PLoS One' (Public Library of Science , Public Library of Science).

    According to the survey conducted by researchers of the Institute of Development Research (IRD), after analysis of 4000 samples of blood taken from the people of Gabon over 15% had antibodies to the Ebola virus, while not never had haemorrhagic fever or other similar symptoms.

    According to experts it is possible that they are probably immune to Ebola in contact with the virus by eating fruit contaminated by the saliva of bats.

    Isolated for the first time in 1976 on the banks of the river Ebola - in the region dell'Equateur in the Democratic Republic of Congo - the virus can cause severe hemorrhagic fever that can reach a mortality rate of 95% of the infected.

    The study began dall'Ird, however, is convinced that continuing with the analysis you may discover that the real danger of virus is much lower than reported so far.

    Outbreaks of Ebola in Gabon appear episodically, Republic of the Congo, Democratic Republic of Congo, Sudan and Uganda.


  • #2
    Re: Large numbers of people in Gabon have antibodies to Ebola

    This is utterly inconsistent with the known epidemiology of Ebola: when an entire family contracts Ebola, most if not all of them die. The epidemiology of Ebola outbreaks is not consistent with large numbers of asymptomatic infections, even if asymptomatic infections could not transmit the virus. If these people were really being exposed by eating fruit contaminated with Ebola virus from bats, they would likely be bleeding to death.

    A very interesting puzzle. Perhaps some other virus or something else in nature is giving these people immunity without an actual Ebola infection. Such a find could easily lead to an Ebola vaccine.


    • #3
      Re: Large numbers of people in Gabon have antibodies to Ebola

      See also the above thread for the full abstract of the article.


      • #4
        Re: Large numbers of people in Gabon have antibodies to Ebola

        Interesting indeed.

        But the #1 finding is corroborated by similar foundings in the wild chimpanzees:

        "A study was published in the Journal of Infectious Diseases in 2004 that brought to light interesting new information on the natural reservoirs of Ebola virus. It was recorded that approximately 13 percent of wild-born chimpanzees had Ebola antibodies in their blood. This finding showed researchers that Ebola virus is and was in circulation in the forests of countries where no human cases have been reported or before it infected humans. It also showed that chimps can be in contact with Ebola and survive, telling also that they have probably been exposed multiple times. An aspect of this research that is very relevant to global health is the possibly that is now known that Ebola can exist in places where it has not been before and could cause human outbreaks in unexpected countries."

        "Depending on the type of virus, Ebola can have up to a 90 percent mortality rate for those infected."

        The antibody presence from the above is 13%, near the 15% in humans from text post #1,
        but it is not probable that all the 15% were the only remained survivors from previous real outbreaks (to fit the 85% ~ 90% mortality, instead of be mostly inconsciously infected outside of known epidemic hot zones.


        • #5
          Re: Large numbers of people in Gabon have antibodies to Ebola

          The outbreak last year (I think it was Uganda? or Congo) had a far lower CFR @30% and was identified as a seperate substrain.

          Perhpas there is an Ebola variant that is far less lethal that circulates almost undetected, and we only recognise outbreaks of the more severe variant. this too could explain such results, but alerts point remains valid. If this is true, it could lead to a vaccine.


          • #6
            Re: Large numbers of people in Gabon have antibodies to Ebola

            I agree Vibrant62. There is much to be learned about the pathogenicity of this group of pathogens.

            There is further evidence of sublethal Ebola (Reston) infection among pigs and humans in the Phillipines:

            It earned the name during an outbreak among monkeys and humans in Reston, VA in the US during 1989 - 1990.

            A nice summary of Ebola outbreaks and strains:
            Separate the wheat from the chaff


            • #7
              Re: Large numbers of people in Gabon have antibodies to Ebola

              The study linked to above indicated that the antibodies were specific to the Zaire ebolavirus, not Reston or Bundibugyo or any other strain, and we believe that Zaire has a 50-90% CFR. I think it is obvious that something other than that virus is giving people immunity to that virus.

              We know that at least one monkey (chimp? ape?) who was infected with Ebola Reston asymptomatically during one of the outbreaks in the Philippines, and later was intentionally in a lab exposed to Zaire ebolavirus without getting ill. Perhaps Reston or another yet to be discovered ebolavirus is doing the same thing in humans in Gabon. That would be a remarkable discovery.


              • #8
                Re: Large numbers of people in Gabon have antibodies to Ebola

                It was in ouganda in 2007 : Bundibugyo strain
                mortality : 25%


                Geneva - The World Health Organisation expressed concern on Friday about the emergence of a new strain of the Ebola virus that has infected 51 people and killed 16 in western Uganda.

                The outbreak, announced by US and Ugandan health officials on Thursday, is in Bundibugyo, near the border with Democratic Republic of Congo.

                Genetic analysis of samples taken from some of the victims shows it is a previously unknown type of Ebola, making it the fifth strain, they said.

                "We do not yet know yet exactly the lethality of this virus because we haven't tested all the samples," WHO spokesman Gregory Hartl told a news briefing in Geneva.

                a small file :

                Ploss :


                • #9
                  Re: Large numbers of people in Gabon have antibodies to Ebola

                  Ebola in Uganda: November 30 - December 17, 2007

                  Ebola: December 18+ 2007, is getting contained


                  • #10
                    Re: Large numbers of people in Gabon have antibodies to Ebola

                    And a ProMED post. If people are immune to Zaire ebolavirus in places where no outbreak has ever been reported, it seems obvious (IMO) that something other than that virus is giving people the immunity.


                    Archive Number 20100212.0496
                    Published Date 12-FEB-2010
                    Subject PRO/AH/EDR> Zaire ebolavirus - Gabon: seroprevalence

                    A ProMED-mail post
                    ProMED-mail is a program of the
                    International Society for Infectious Diseases

                    Date: Tue 9 Feb 2010
                    Source: PLoS (Public Library of Science) ONE [edited]

                    [Reference: Becquart P, Wauquier N, Mahlakoiv T, et al: High
                    prevalence of both humoral and cellular immunity to Zaire ebolavirus
                    among rural populations in Gabon. PLoS ONE 5(2): e9126.
                    [The authors are located at the Emerging Viral Diseases Unit,
                    International Centre of Medical Research, Franceville, Gabon; UMR190
                    Emergence of Viral Pathologies, Aix-Marseille II University &
                    Research Institute for Development, Marseille, France; and Mahidol
                    University at Salaya, Nakhonpathon, Thailand]

                    To better understand Zaire ebolavirus circulation and transmission to
                    humans, we conducted a large serological survey of rural populations
                    in Gabon, a country characterized by both epidemic and non epidemic
                    regions. The survey lasted 3 years and covered 4349 individuals from
                    220 randomly selected villages, representing 10.7 percent of all
                    villages in Gabon. Using a sensitive and specific ELISA method, we
                    found a Zaire ebolavirus-specific IgG seroprevalence of 15.3 percent
                    overall, the highest ever reported. The seroprevalence rate was
                    significantly higher in forested areas (19.4 percent) than in other
                    ecosystems, namely grassland (12.4 percent), savannah (10.5 percent),
                    and lakeland (2.7 percent). No other risk factors for seropositivity
                    were found. The specificity of anti-Zaire ebolavirus IgG was
                    confirmed by Western blot in 138 individuals, and CD8 T cells from 7
                    IgG+ individuals were shown to produce IFN-gamma after Zaire
                    ebolavirus stimulation.

                    Together, these findings show that a large fraction of the human
                    population living in forested areas of Gabon has both humoral and
                    cellular immunity to Zaire ebolavirus. In the absence of identified
                    risk factors, the high prevalence of "immune" persons suggests a
                    common source of human exposure such as fruits contaminated by bat
                    saliva. These findings provide significant new insights into Zaire
                    ebolavirus circulation and human exposure, and raise important
                    questions as to the human pathogenicity of Zaire ebolavirus and the
                    existence of natural protective immunization.

                    Communicated by:

                    [The following extract from this paper provides the background to
                    this study and puts the data in perspective. Interested readers
                    should consult the full text and references via the URL at top of this report.

                    "Zaire ebolavirus is the most pathogenic ebolavirus species, with
                    reported case fatality rates of up to 90 percent. Zaire ebolavirus
                    has caused several outbreaks in Central Africa, Democratic Republic
                    of Congo (DRC), Republic of Congo (RC), and Gabon. North-east Gabon
                    experienced 4 outbreaks between 1994 and 2002, with a total of 259
                    confirmed human cases and only 79 survivors (case fatality rate: 69 percent)."

                    "Recently, significant advances have been made in our understanding
                    of filovirus ecology. Antibodies and nucleotide sequences specific
                    for Zaire ebolavirus have been detected in the liver and spleen of 3
                    fruit bat species in Gabon and RC (_Hypsignathus monstrosus_,
                    _Epomops franquetti_, and _Myonycteris torquata_), and antibodies and
                    nucleotide sequences specific for Marburg virus have been found in a
                    fruit bat species in Gabon (_Rousettus aegyptiacus_) and in 2
                    insectivorous bat species in DRC (_Rhinolophus eloquens_ and
                    _Miniopterus inflatus_). More recently, this virus was isolated for
                    the 1st time in cave-dwelling _Rousettus aegyptiacus_ in Uganda.
                    Together, these findings raise the possibility that these bats might
                    be a filovirus reservoir, but the mechanism of primary Zaire
                    ebolavirus transmission to humans, potentially leading to outbreaks,
                    remains unclear. Ebola hemorrhagic fever outbreaks that occurred in
                    Gabon and RC between 2001 and 2003 were also associated with major
                    outbreaks among wild-living large mammals (especially chimpanzees and
                    gorillas), devastating local animal populations. The primary human
                    cases involved hunters who became infected after handling animal
                    carcasses found in the forest. Similarly, the 1996 Mayibout outbreak
                    in Gabon started among children who handled a chimpanzee carcass. A
                    recent study showed that the 2007 Luebo outbreak in DRC was linked to
                    massive fruit bat migration, strongly suggesting for the 1st time
                    that humans could be infected directly by bats."

                    "It is generally accepted that Zaire ebolavirus is associated with a
                    case fatality rate of about 90 percent, but this may be an
                    overestimate. For example, 7 cases of asymptomatic infection were
                    identified during the 1996 Booue outbreak in Gabon, and some
                    ELISA-based serosurveys have shown high antibody prevalence rates
                    among populations living in areas where no case of Ebola hemorrhagic
                    fever has ever been reported
                    , suggesting that Zaire ebolavirus might
                    also be capable of causing mild illness or even asymptomatic
                    infection in humans. The IgG seroprevalence was 9.3 percent in
                    villages located in the 1995 outbreak area around Kikwit, DRC, where
                    no Ebola haemorrhagic fever cases were reported. Likewise, a
                    seroprevalence of 13.2 percent was found in the Aka Pygmy population
                    of Central African Republic, where no Zaire ebolavirus outbreaks have
                    ever been reported."

                    "The source and significance of anti-Zaire ebolavirus IgG
                    seropositivity among people who have never had clinical signs of
                    haemorrhagic fever or who live in non epidemic areas are both
                    unclear, but they may have major implications for our understanding
                    of the epidemiology of Zaire ebolavirus primary transmission to
                    humans and outbreaks."

                    "This study provides important insights into Zaire ebolavirus
                    circulation, human exposure and pathogenicity, and outbreak
                    occurrence. The high frequency of 'immune' individuals with no
                    disease or outbreak history raises questions as to the real
                    pathogenicity of Zaire ebolavirus for humans in 'natural' conditions.
                    Added to the lack of identifiable risk factors, this points to bats
                    as the main source of human exposure, through handling and ingestion
                    of contaminated fruits. Past outbreaks in which no animal source was
                    identified may have been due to fruit bat activity close to the
                    villages concerned. Rural populations living in forested regions of
                    the central African forest block thus appear to be highly exposed to
                    the virus. More and more viruses are being detected in bats, some of
                    which are known to be pathogenic for humans."

                    The authors' conclusion that transmission of infection via fruit
                    contaminated by bat saliva has also been suggested as a route of
                    disease transmission in the case of Nipah virus infection in Asia
                    (such as, ProMED-mail post -- Nipah virus, fatal - Bangladesh: (FR)

                    The HealthMap/ProMED-mail interactive map of Gabon can be accessed at
                    <>. - Mod.CP]


                    • #11
                      Re: Large numbers of people in Gabon have antibodies to Ebola

                      the main conclusion from the study background:
                      "suggesting that Zaire ebolavirus might also be capable of causing mild illness or even asymptomatic infection in humans"

                      near forest communities could eats more bats saliva fresh contaminated fruits and were subjected to more severe illness,
                      and maybe
                      the other non bats distant places could had the contacts by similar traded bat contaminated bush fruits, which saliva because of sun, time and handlings, loosed some of the infectious and harming capabilities, so it inflicts mainly lower harms