Acta Tropica 76 (2000) 119–124

Longstanding presence of HIV-2 infection in Guinea-Bissau(West Africa)

Joao Piedade a,*, Teresa Venenno a, Emılia Prieto b, Rita Albuquerque a,c,Aida Esteves a, Ricardo Parreira a, Wanda F. Canas-Ferreira a

a Unidade de Virologia, Instituto de Higiene e Medicina Tropical, Uni6ersidade No6a de Lisboa, Lisbon, Portugalb Unidade de Doencas Sexualmente Transmitidas, Instituto de Higiene e Medicina Tropical, Uni6ersidade No6a de Lisboa,

Lisbon, Portugalc Departamento de Microbiologia, Faculdade de Ciencias Medicas, Uni6ersidade No6a de Lisboa, Lisbon, Portugal

Received 11 November 1999; received in revised form 28 February 2000; accepted 14 March 2000

Abstract

We have retrospectively studied the seroprevalence of the human immunodeficiency virus (HIV) in Guinea-Bissauin a sample of sera collected from the whole country in 1980. We tested a total of 1248 individuals and found 11individuals who were seropositive for HIV-2 but there were no HIV-1 seropositive samples. The mean age of theHIV-2 seropositive people was significantly higher than the age of the seronegative individuals. In the different areassurveyed, the HIV-2 seroprevalence ranged from 0 to 2.5%. A central region of the country, grossly centred in thecapital city of Bissau, presented the highest prevalence of HIV-2 seropositivity (\2%), which contrasts with its virtualabsence from the more remote rural areas located near the borders with the neighbouring countries. The overallseroprevalence found for HIV-2 in this study is 0.9% (1.8%, when considering the adult seroprevalence only), whichproves that the virus was definitely circulating in Guinea-Bissau at the beginning of the 1980s. © 2000 ElsevierScience B.V. All rights reserved.

Keywords: HIV-2; Guinea-Bissau; West Africa

www.elsevier.com/locate/actatropica

1. Introduction

Over two-thirds of people presently infectedwith the human immunodeficiency virus (HIV)

live in sub-Saharan Africa and a total of 83% ofthe world’s AIDS deaths have occurred in thisregion (WHO/UNAIDS, 1998). The cocirculationof HIV-1 and HIV-2 in Africa, especially in WestAfrica (De Cock et al., 1993), is recognised sincetheir discovery as causative agents of AIDS(Barre-Sinoussi et al., 1983; Clavel et al., 1987).HIV-2 is endemic in this area, reaching its highestprevalence in Guinea-Bissau, where one can findup to 8–10% HIV-2-seropositive people in the

* Corresponding author. Present address: Instituto deHigiene e Medicina Tropical (UNL), Unidade de Virologia,Rua da Junqueira, 96, P-1349-008 Lisbon, Portugal. Tel.:+351-21-3652600; fax: +351-21-3632105.

E-mail address: jp@ihmt.unl.pt (J. Piedade).

0001-706X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.

PII: S 0001 -706X(00 )00096 -6

J. Piedade et al. / Acta Tropica 76 (2000) 119–124120

general population (Pinto et al., 1991; Poulsen etal., 1993; Wilkins et al., 1993). Although rarelyfound, HIV-2 infection has been described outsideWest Africa, especially in people epidemiologi-cally linked with that region. In Portugal, forinstance, where strong social, economical and cul-tural ties with West Africa are maintained, about4.5% of the total AIDS cases are caused by HIV-2(Comissao Nacional de Luta Contra a SIDA,1999).

Although there is still some uncertainty aroundthe origin of HIV-1 (Sharp et al., 1999), thebiological origins of HIV-2 seem to be evident. Itis assumed that HIV-2 is phylogenetically closelyrelated to SIV from sooty mangabeys (SIVSM).These monkeys (Cercocebus torquatus atys) areindigenous to West Africa and are infected withSIVSM at high rates in the wild. Sooty mangabeysare also commonly hunted for food and kept aspets in this region of the world and it is easy toenvisage a cross-species transmission to humans(Sharp et al., 1999), probably on more than oneoccasion. It seems, therefore, plausible that WestAfrica, and probably Guinea-Bissau, could be theprimordial geographic origin of HIV-2 infection.

Epidemiological studies indicate that HIV-2 hasbeen present in the human population from thatgeographic region for many decades (Marlink,1996).

In order to investigate the widespread circula-tion of HIV-2 in the population of Guinea-Bissauin the beginning of the 1980s, we have retrospec-tively studied a sample of 1248 sera for the pres-ence of HIV-2 antibodies. The sera had beencollected mainly in rural settings of that WestAfrican country and stored in our laboratorysince then.

2. Patients and methods

A sample comprising 1248 sera, originally col-lected in 1980 for a seroepidemiological study ofyellow fever infection in Guinea-Bissau, was se-lected for this study. After their arrival to ourlaboratory in Lisbon, the samples were thawedand refrozen just once, for the original study, andkept frozen at −20°C, since then. The group ofGuinean individuals invited to participate in theoriginal study comprised apparently healthy vil-lagers and included 587 males (47.0%) and 659females (52.8%), with two individuals of unknowngender. All the enrolled individuals, or their par-ents (if underage), gave their informed consentand were submitted to blood sample collectionand to a basic demographic questionnaire. Theirages ranged from 1 to 75 years (two individualswith age not reported), with an average of 17.1years. All the main Guinean ethnic groups wererepresented in the sample, with proportions simi-lar to those found in the country’s populationstructure (data not shown). The sample collectionpoints are depicted in Fig. 1. Geographically, thestudy covered almost the entire country, includingthe insular regions (archipelago of Bijagos), withthe exception of the south-eastern region alongthe border with Republic of Guinea.

The initial screening for HIV antibodies in thesera was carried out by ELISA (Innotest HIV1/HIV2 Ab s.p., Innogenetics, Belgium). The posi-tive results were confirmed using commercialHIV-1 and HIV-2 Western Blots (WB) (NewLAV Blot I and II, Sanofi Diagnostics Pasteur,

Fig. 1. Map of Guinea-Bissau showing the localisation of thedifferent collection points and the major urban centres (key:1–Canquelifa; 2–Buruntuma; 3–Pirada; 4–Sare Bacar; 5–Bafata; 6–Cuntim; 7–Guidaje; 8–Ingore; 9–Sao Domingos;10–Bubaque; 11–Quinhamel; 12–Canchungo; 13–Buba; 14–Catio; 15–Cacine).

J. Piedade et al. / Acta Tropica 76 (2000) 119–124 121

Table 1Characteristics of the HIV-2 seropositive subjects

Age Ethnic groupSample identification LocationGender

41505 PapelMale Bafata53 FulaFemale Bafata154826 Banhul1682 CuntimMale20 MandingaFemale Guidaje2421

Female3215 31 Papel Bubaque31 BijagosFemale Bubaque322652 Papel3323 QuinhamelFemale50 PapelFemale Quinhamel3324

3458 5Female Mixed Quinhamel30 MandingaFemale Canchungo3623

5257 59Male Fula Buba

Table 2Seroprevalence of HIV-2 infection by age group

HIV-2 seronegativesAges TotalHIV-2 seropositives HIV-2 seropositivity (%)

B15 7332 735 0.3288 2902 0.715–29

330–44 150 153 2.063 674 6.0]45

1234Total 1245a11 0.9

a 3/1248 individuals reported unknown age.

France), performed following the manufacturer’sinstructions, and seropositivity established ac-cordingly with the World Health Organisation(WHO) interpretation criteria.

Statistical analysis included, when appropriate,P-values of the x2 test with Yates’ correction,Student’s t-test and Fisher’s exact test (gener-alised to r×c tables, with r, c\2) using pro-gramme STATA 5.0.

This sero-archeological study was performed inaccordance with a protocol approved by the Sci-entific Council of our institution.

3. Results

The overall seroprevalence of HIV-2 among the1248 screened individuals throughout Guinea-Bis-sau was 0.9% (11/1248). Six individuals (0.5%)were HIV-2 seropositive, with no reactivity at allfor HIV-1 in the WB. The remaining 5 (0.4%),

besides being HIV-2 seropositive, showed a vari-able degree of reactivity for HIV-1 in the WB,however, never fulfilling the WHO positivity crite-ria. There was no exclusively HIV-1 seropositivesample. Based on these results and in known dataabout the natural history of HIV-1 infection inGuinea-Bissau (Larsen et al., 1998), we consideredthe serologic profiles of the second group as trueHIV-2 infections with some degree of cross-reac-tivity for HIV-1.

From the 11 HIV-2 seropositive individuals,eight (72.7%) were women and three (27.3%) weremen (Table 1). There was no statistical associationbetween gender and HIV-2-seropositivity (x2 testwith Yates’ correction, P\0.25). Mean age of theHIV-2 seropositive people was significantly higher(32.8 years, S.D. 18.9) compared with seronega-tive people (16.9 years, S.D. 13.4) (Student’s t-test, PB0.001). HIV-2 seroprevalence issignificantly higher amongst older age groups(Fisher’s exact test, PB0.0001), reaching as much

J. Piedade et al. / Acta Tropica 76 (2000) 119–124122

as 6.0% for people more than 45 years old (Table2). When considering adult (]15 years) HIV-2seroprevalence only, one can find a value of 1.8%,which is twice the overall seropositivity rate(0.9%). No association between ethnic group andHIV-2-seropositivity was found (data not shown)and the 11 seropositive individuals (Papel, 4;Fula, 2; Mandinga, 2; others, 3) were grosslydistributed according to the ethnic structure of thesample. The HIV-2 seropositive cases do not seemto be randomly distributed through the country(Fig. 1). The seropositive samples were collectedfrom seven different locations (Canchungo, Cun-tim, Guidaje, Buba, Bafata, Bubaque and Quin-hamel), with HIV-2 seropositivity rate rangingbetween 0.8 (in Canchungo) and 2.5% (in Quin-hamel). Furthermore, there seems to be a ‘HIV-2seropositivity area’, roughly centred on Bissau,the capital city. It is noteworthy that five of thepositive samples (45.5% of the total) were fromQuinhamel and Bubaque alone, which are placeswith frequent social and commercial links withBissau. On the other hand, in 1980, HIV-2 infec-tion was absent from eight out of the 15 placessurveyed, especially those located in the southernand north-eastern tips of the country and fartherfrom the two major urban centres of Bafata andBissau.

4. Discussion

The geographical distribution and biologicalorigins of HIV-2 are reasonably understood.There is enough evidence to speculate about itsorigins in foci of infection probably developed inthe 1970s in some West African countries, mostprobably Guinea-Bissau and/or Ivory Coast(Remy, 1998). The virus was dispersed in coun-tries close to these primary Guinean and Ivorianfoci, although in a limited way, probably by themigration of workers and prostitutes. Especiallyfor the first case, the decolonization-related mas-sive movement of people is surely linked to thedispersal of the virus also to historically associ-ated countries both in Africa (Angola, Mozam-bique) and in other continents (Portugal, Brazil,India). The epidemiological link between Portugal

and its former colonies in Africa was fully recog-nised for several cases of retrospectively well doc-umented HIV-2 infection cases in Europe in thelate 1970s (Ancelle et al., 1987; Saimot et al.,1987; Bryceson et al., 1988). Although most Eu-ropean countries can presently link the presenceof HIV-2 within their country to ties with WestAfrica, France and Portugal now report HIV-2infection among the indigenous population. InPortugal, 4.5% of the total cumulated AIDS re-ported cases are due to HIV-2 infection and about60% of these cases are no longer directly linked toWest African contacts (Quinn, 1994).

The presence of HIV-2 infection in some WestAfrican countries as early as 1965 was docu-mented, with a seroprevalence ranging between0.3 and 2.5% (Kawamura et al., 1989; Le Guenno,1989). To our knowledge, only one sero-archeo-logical study was made regarding the presence ofHIV-2 in Guinea-Bissau before 1986 (Fultz et al.,1988). This study reported that at least 1.4% of arandom sample of people in rural Guinea-Bissauhad been exposed to HIV-2 in the early 1980s. Wehave, therefore, decided to retrospectively studythe seroprevalence of HIV-2 in a group of 1248serum samples collected in 1980 originally to testfor the prevalence of antibodies to yellow fevervirus in healthy people mainly living in rural areasof Guinea-Bissau. Overall, we found in the stud-ied population a HIV-2 seroprevalence of 0.9%(11/1248), apparently unevenly distributedthroughout the country. Its central region, includ-ing the insular area of Bijagos, seems to have thehighest prevalence of HIV-2 seropositivity (\2%), which contrasts with its virtual absence frommore remote rural areas located near the bordersof the neighbouring countries Senegal and Repub-lic of Guinea. Therefore, the circulation of thevirus (HIV-2) seems to have been focused in thecentral regions of Guinea-Bissau, most probablyin Bissau, the capital city. It is interesting to notethat the two places showing the highest seropreva-lence for HIV-2 (Quinhamel and Bubaque) havenarrow social and commercial contacts with Bis-sau. Quinhamel is not far from Bissau andBubaque is the main town in the island with thesame name in archipelago of Bijagos and it iseasily reached from Bissau by ferryboat. Unfortu-

J. Piedade et al. / Acta Tropica 76 (2000) 119–124 123

nately, we do not have any samples from Bissauin this study, but in our oldest samples fromthere (n=3960), dating back to 1986, we founda HIV-2 seropositivity rate of 8.2% (7.3–9.1%,95% CI) (unpublished results), indicating a viralwell-established circulation. We know, from pre-vious studies, that demographic, social and cul-tural conditions for the transmission ofblood-borne pathogens (namely HIV) are com-mon in Guinea-Bissau, especially in Bissau,where a major portion (�20%) of the inhabi-tants of the country lives. It is possible thatBissau, as described for other major cities inthat region of Africa, functioned as a diffusionfocus of the infection for more distant rural set-tings during the 1980s. Another interesting con-clusion drawn from this study is that HIV-2seroprevalence is significantly higher amongstolder age groups (Table 2), which together withthe known seroprevalence data from the 1960/1970s relative to the neighbouring countriesSenegal, Mali and Ivory Coast (Kawamura etal., 1989; Le Guenno, 1989), has led to specula-tion that the virus was obviously not new toGuinea-Bissau in 1980. However, its low sero-prevalence in vast rural areas of the territoryseems to indicate that it was probably spreadingwithin the country at a very slow rate.

Acknowledgements

We are very grateful to all those people whohelped in the collection of the sera throughoutGuinea-Bissau. Luzia Goncalves (Unidade deEpidemiologia e Biostatıstica, IHMT) is also ac-knowledged for helping in the statistical analy-sis. This work was partially supported byUPMM/FCT (Portugal).

References

Ancelle, R., Bletry, O., Baglin, A.C., Brun-Vezinet, F., Rey,M.-A., Godeau, P., 1987. Long incubation period forHIV-2 infection. Lancet 1, 688–689.

Barre-Sinoussi, F., Chermann, J.C., Rey, F., Nugeyre, M.T.,Chamaret, S., Gruest, J., Dauguet, C., Axler-Blin, C.,

Vezinet-Brun, F., Rouzioux, C., Rozenbaum, W., Montag-nier, L., 1983. Isolation of a T-lymphotropic retrovirusfrom a patient at risk for acquired immune deficiencysyndrome (AIDS). Science 220, 868–871.

Bryceson, A., Tomkins, A., Ridley, D., Warhurst, D., Gold-stone, A., Bayliss, G., Toswill, J., Parry, J., 1988. HIV-2-associated AIDS in the 1970s. Lancet 2, 221.

Clavel, F., Mansinho, K., Chamaret, S., Guetard, D., Favier,V., Nina, J., Santos-Ferreira, M.O., Champalimaud, J.L.,Montagnier, L., 1987. Human immunodeficiency virus type2 infection associated with AIDS in West Africa. N. Engl.J. Med. 316, 1180–1185.

Comissao Nacional de Luta Contra a SIDA, 1999. SIDA: asituacao em Portugal a 30 de Junho de 1999. Centro deVigilancia Epidemiologica das Doencas Transmissıveis, In-stituto Nacional de Saude, Lisboa, Portugal.

De Cock, K.M., Adjorlolo, J., Ekpini, E., Sibailly, T., Koua-dio, J., Maran, M., Brattegaard, K., Vetter, K.M., Doorly,R., Gayle, H.D., 1993. Epidemiology and transmission ofHIV-2. Why there is no HIV-2 pandemic. JAMA 270,2083–2086.

Fultz, P.N., Switzer, W.M., Schable, C.A., Desrosiers, R.C.,Silva, D.P., McCormick, J.B., 1988. Seroprevalence ofHIV-1 and HIV-2 in Guinea Bissau in 1980. AIDS 2,129–132.

Kawamura, M., Yamazaki, S., Ishikawa, K., Kwofie, T.B.,Tsujimoto, H., Hayami, M., 1989. HIV-2 in West Africa in1966. Lancet 1, 385.

Le Guenno, B., 1989. HIV1 and HIV2: two ancient viruses fora new disease? Trans. R. Soc. Trop. Med. Hyg. 83, 847.

Larsen, O., Silva, Z., Sandstrom, A., Andersen, P.K., An-dersson, S., Poulsen, A.-G., Melbye, M., Dias, F., Naucler,A., Aaby, P., 1998. Declining HIV-2 prevalence and inci-dence among men in a community study from Guinea-Bis-sau. AIDS 12, 1707–1714.

Marlink, R., 1996. Lessons from the second AIDS virus.AIDS 10, 689–699.

Pinto, A.S., Canas-Ferreira, W.F., Costa, C., Silva, A.P.,Alvarez, E.P., Sousa, R.A., Mansinho, K., Champalimaud,J.L., Araujo, C., Dias, F., Monteiro, J., Venenno, T.,Piedade, J., 1991. Immunologic profile of HIV-2 seroposi-tive African individuals (follow-up). Acta Med. Port. 4,64S–66S.

Poulsen, A.-G., Aaby, P., Gottschau, A., Knivesdal, B.B.,Dias, F., Molbak, K., Lauritzen, E., 1993. HIV-2 infectionin Bissau, West Africa, 1987–1989: incidence, prevalence,and routes of transmission. J. Acquired Immune Defic.Syndr. Hum. Retrovirol. 6, 941–948.

Quinn, T.C., 1994. Population migration and the spread oftypes 1 and 2 human immunodeficiency viruses. Proc. Natl.Acad. Sci. USA 91, 2407–2414.

Remy, G., 1998. HIV-2 infection throughout the world. Ageographical perspective. Cahiers Sante 8, 440–446.

Saimot, A.G., Coulaud, J.P., Mechali, D., Matheron, S.,Dazza, M.C., Rey, M.A., Brun-Vezinet, F., Leibowitch, J.,

J. Piedade et al. / Acta Tropica 76 (2000) 119–124124

1987. HIV-2/LAV-2 in Portuguese man with AIDS(Paris, 1978) who had served in Angola in 1968–1974.Lancet 1, 688.

Sharp, P.M., Bailes, E., Robertson, D.L., Gao, F., Hahn,B.H., 1999. Origins and evolution of AIDS viruses. Biol.Bull. 196, 338–342.

WHO/UNAIDS, 1998. Report on the global HIV/AIDS epi-demic. WHO/UNAIDS, Geneva.

Wilkins, A., Ricard, D., Todd, J., Whittle, H., Dias,F., Silva, A.P., 1993. The epidemiology of HIVinfection in a rural area of Guinea-Bissau. AIDS 7,1119–1122.

.