WHO/GPNCNP/EVN93.1 Original: English Distr.: General GLOBAL PROGRAMME THE HIV/AIDS PANDEMIC: 1993 OVERVIEW WORLD HEALTH ORGANIZATION

Transcription

1 WHO/GPNCNP/EVN93.1 Original: English Distr.: General GLOBAL PROGRAMME THE HIV/AIDS PANDEMIC: 1993 OVERVIEW WORLD HEALTH ORGANIZATION

2 <0 Wrld Health Organizatin 1993 This dojment is nt a frmal publicaun f the Wrk1 Health OrganizaUn (WHO). and all riglts are r9sqrved by ttle Organizatin. The dcunt may. hwever. be freely reviewed. abstracted. reprduced r translated. n part r in whle. but nt fr sale r fr use in cnjuncoon with mmerdal purpses. The views expressek1 in IMnts by nard auth15 are slely the respnsibility f!tlse aurs.

3 WHO/GPA/CNP/EV M3.1 THE HIV/AIDS PANDEMIC: 1993 OVERVIEW CONTENTS I. Intrductin. 1 a. The HIVIAIDS pandemic. 1 b. Mdes fhiv transmissin. 4 c. Prgressin frm HIV infectin t illness. 5 d. Interactins between "HIV infectin and ther diseases. 6 II. Extent and gegraphical distributin f HIV infectin and AIDS Australasia, Nrth America and Western Eurpe. 7 Latin America and the Caribbean. 8 Sub-Saharan Africa. 9 Suth and Suth-East Asia. 11 East Asia and the Pacitic 13 Eastern Eurpe and Central Asia. 13 Nrth Africa and the Middle East. 14 III. Glbal estimates and prjectins f HIV I AIDS. 15

4 WHO/GPA/CNP/EV An3.1 Page 1 I. Intrductin a. The HIVIAIDS pandemic In 1981 a new syndrme, the acquired immundeficiency syndrme (AIDS), was first recgnized amng hmsexual men in the USA. By 1983 the etilgical agent -the human immundeficiency virus (HIV) -had been identified. By the mid 1980s it became clear that the virus had spread, largely unnticed, thrughut the wrld and that its effects had reached truly glbal -r "pandemic" -prprtins. The HIV/AIDS within a single cuntry). pandemic cnsists f many separate epidemics (in many cases even Each epidemic has its wn distinct rigin, in terms f gegraphy and specific ppulatins affected, and invlves different types and frequencies f risk behaviurs and practices -fr sharing drug injectin equipment. example, having unprtected sex with multiple partners r The extensive spread f HIV appears, in retrspect, t have cmmenced in the late 1970s r early 1980s -in the Americas, Australasia and Western Eurpe primarily in hmsexual r bisexual men and injecting drug users in certain urban areas; and in parts f the Caribbean and East and Central Africa amng men and wmen with multiple sex partners. Tday, the virus is being transmitted n all cntinents. As f mid 1993, mre than 14 millin HIV infectins are estimated t have ccurred since the beginning f the pandemic, ver 13 millin f them in adults (Figure I; Table I ). Figure I. Estimated glbal distributin f cumulative HIV infectins in adults, by cntinent r regin -mid 1993

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6 WHO/GPA/CNP/EV 3.1 Page 3 The HIV / AIDS pandemic was initially centred in urban lcatins but in mst cuntries is nw thught t be present in rural areas as well. The precise nature and extent f HIV spread in rural areas varies between, and even within, individual cuntries and is largely influenced by the transprtatin infrastructure. Initially, in develped cuntries, men were mre expsed t HIV than wmen, primarily as a result f hmsexual intercurse r drug injecting, but the difference in the numbers f men and wmen infected with HIV has gradually narrwed as hetersexual transmissin has becme mre cmmn. In ther parts f the wrld, where hetersexual transmissin predminated frm the utset, the difference between the sexes is even narrwer. Wrldwide, there are 3 men already infected fr every 2 wmen (see Table 1) and by the year 2000 the number f new infectins amng wmen is expected t apprach that amng men. The rising infectin rates in wmen are accmpanied by a crrespnding rise in the number f children brn with HIV infectin. T date, it is estimated that abut 1 millin children have been infected with HIV thrugh mther-t-child transmissin. These children rapidly develp AIDS and die -usually befre the age f 5. Tw sertypes f HIV are currently recgnized, namely HIV -I and HIV -2. Wrldwide, the predminant virus is HIV-I. Hwever, HIV-2 appears t have spread extensively during the 1980s, principally in West Africa, althugh spradic infectins with this sertype have QOW been reprted frm East Africa t, as well as frm Eurpe, Asia and " Latin America. The mdes f transmissin f HIV -2 are similar t thse fr HIV -I, and the tw viruses appear t cause clinically indistinguishable AIDS. Hwever, HIV -2 may be less easily transmitted, and the perid between initial infectin and illness may be lnger in the case f HIV-2. In the light f recent reprts f cases f severe immundepressin in the absence f either HIV-I r HIV-2 infectin, cncern has been raised that anther, as yet undetected, virus may be spreading. Between June and September 1992 a wrldwide investigatin was cnducted by WHO and the US Centers fr Disease Cntrl and Preventin. N evidence f a link between the cases r f a new HIV -like virus was fund. By Janu'flry 1993, mre than AIDS cases had been reprted t WHO (Table 1 ), but WHO estimates that as f mid 1993, allwing fr under-diagnsis, underreprting, and delays in reprting, there have been mre than 2.5 millin cumulative AIDS cases wrldwide (Figure 2). Of these, it is estimated that mre than are paediatric AIDS cases resulting frm mther-t-child transmissin, almst all f these having ccurred in sub-saharan Africa.

7 WHO/GPA/CNP/EV 3.1 Page 4 Figure 2. Cumulative AIDS cases in men, wmen and children Reprted: Estimated: > Excluding USA I As f January As f June 1993 b. Mdes fhiv transmissin An understanding f the ways in which HIV can be transmitted is central t an understanding f the epidemilgy f the pandemic. It has nw been established, as a result f labratry and epidemilgical investigatins, that HIV is transmitted in three ways: thrugh sexual intercurse, thrugh bld and frm mther t child. HIV transmissin as a result f sexual intercurse accunts fr abut three-quarters f all HIV infectins wrldwide. In ther wrds, HIV infectin is a sexually transmitted disease (STD). Transmissin thrugh intercurse between men ccurs in mst parts f the wrld, althugh in the develped cuntries it has becme far less cmmn thanks t the adptin f safer sex practices by hmsexual men. The majrity f the wrld's infectins have been acquired thrugh intercurse between men and wmen (hetersexual transmissin). This mde f transmissin cntinues t grw in imprtance wrldwide.

8 WHO/GPA/CNP/EV 3.1 Page S As with cenain ther STDs, HIV infectin can als be transmitted thrugh bld, fr example as a result f the medical transfusin f infected bld r bld prducts. In many pans f the wrld prgress twards a safer supply f bld and bld prducts is being achieved thrugh the apprpriate selectin f dnrs, the screening f dnated bld, and thrugh mre ratinal use f bld aimed at decreasing the number f peple being transfused. Less cmmnly, HIV is als transmitted thrugh the use f nn-sterilized skinpiercing instruments, bth in health facilities (nscmial transmissin, mstly ccurring frm patient t patient) and utside the health care setting. A majr prblem in bth the develped and develping wrld is HIV transmissin resulting frm the use f cntaminated injectin equipment by drug users. The transmissin f HIV frm mther t child includes transmissin during pregnancy, during delivery and thrugh breast-feeding. Overall, apprximately ne third f children brn t HIV -infected mthers will be infected with HIV. Much f mther-t-child transmissin ccurs during pregnancy and delivery, althugh up t half f all HIV infectins frm an infected mther t an uninfected child are believed t ccur thrugh breast-feeding. Labratry -and epidemilgical studies have als shwn that HIV is nt transmitted by everyday cntact, by hugging r kissing, thrugh fd r water, r by msquits and ther biting insects. c. Prgressin frm HIV infectin t illness The interval between infectin with HIV and the nset f clinical symptms is unusually lng cmpared with ther cmmunicable diseases, and varies cnsiderably between individuals. Apprximately 50% f thse infected becme ill within ten years f initial infectin. Current evidence suggests that, in the absence f ther causes f death, almst all HIV -infected peple will ultimately die f AIDS. Once an individual develps AIDS, the average survival time appears t be between ne and three years. Less is knwn f the natural histry f HIV -2 infectins, althugh the evidence t date suggsts that peple infected with HIV -2 prgress t AIDS cnsiderably mre slwly than thse infected with HIV -I. Several factrs may influence the rate f prgressin frm HIV infectin t nset f clinical illness,- Sme strains f HIV may be mre pathgenic than thers. Human genetic factrs andcther hst-specific factrs may affect the rate at which different individuals develp disease. Yet ther factrs, including cncurrent infectins, may als playa rle. There is clear evidence that yung children and adults ver 40 years f age prgress t disease faster than yung adults.

9 WHO/GPA/CNP/EV 3.1 Page 6 d. Interactins between HIV infectin and ther diseases The transmissin f ther sexually transmitted diseases, including gnrrhea, syphilis and chancrid, is assciated with the same behaviurs that expse individuals t ptential HIV infectin and ultimately AIDS. Furthennre, data suggest that STDs - especially thse such as chancrid and syphilis, which cause ulcerative lesins -greatly facilitate bth the acquisitin and transmissin f HIV. Fr bth these reasns, effective STD diagnsis, care and educatin are imperative fr the preventin f HIV infectin. Plicies have been develped by WHO t prvide a basis and a framewrk fr the develpment, strengthening and implementatin f Sill prgrammes. Hwever, since Sill cntrl relies heavily n the extent and quality f health care prvisin, the general perfrmance f the health care system in individual cuntries may largely determine the degree t which Sills can be prevented, r diagnsed and treated. Abut 30% t 50% f adults in mst develping cuntries have latent tuberculsis infectin -i.e., they have been infected with Mycbacterium tuberculsis at sme pint in their lives, but have nt develped active tuberculsis., Tuberculsis is already ne f the leading causes f adult death in many develping cuntries, killing arund 3 millin peple a year.an alarming increase in cases has been reprted in parallel with the AIDS epidemic in many cuntries. HIV infectin is nw the strngest knwn risk factr fr the develpment f acive tuberculsis. Peple with latent tuberculsis infectin mre readily develp the disease nce their immune system has been damaged by HIV. As many as 8% f these dually infected peple may develp active tuberculsis each year. The increased risk f tuberculsis is nt cnfined t HIV -infected peple, hwever. Abut half f all dually infected peple will develp cntagius tuberculsis and be capable f spreading the disease t any susceptible individual. This may cnsequently lead t a dramatic increase in tuberculsis cases amng peple wh are nt infected with HIV.

10 WHO/GPA/CNP/EV M3.1 Page 7 II. Extent and gegraphical distributin f HIV infectin and AIDS This sectin illustrates sme f the recent characteristics and trends in the spread f HIV/AIDS, with emphasis n the regins in which the virus has been spreading fr the lngest time and where the pandemic is thus best understd. Australasia, Nrth America and Western Eurpe In Austral-ia, Nrth America and Western Eurpe, HIV began t spread extensively in the late 1970s t early 1980s. The peple predminantly affected thus far have been hmsexual r bisexual men and injecting drug users, tgether with their sex partners. As f mid 1993, ver 1.5 millin cumulative HIV infectins in adults are estimated t have ccurred in this regin, with abut tw-thirds, r I millin infectins, ccurring in the USA. In ttal abut cumulative AIDS cases in adults and children have been reprted but ver cases are estimated by WHO t have ccurred (Table I ). Marked d!fferences cntinue t exist between and even within these cuntries in the distributin f AIDS cases amng hmsexual men and injecting drug users, reflecting the variability in HIV transmissin patterns. Fr example, n the west cast f the USA, abut 90% f the ttal number f peple with AIDS have been hmsexual men, while n the east cast up t 40% have been injecting drug users. Similarly in Eurpe, the vast majrity f AIDS cases in Scandinavia have ccurred in hmsexual men, whereas injecting drug users cnstitute tw-thirds r mre f the AIDS cases reprted frm Italy and Spain. HIV incidence amng hmsexual men appears t have decreased markedly since the mid 1980s. In cntrast, HIV incidence amng injecting drug users is cntinuing t increase in many places; in Eurpe this transmissin rute accunts fr abut 30% f recent AIDS cases, up frm abut 20% in the mid 1980s. The transmissin f HIV thrugh hetersexual intercurse increased during the latter half f the 1980s and the early 1990s, with especially nticeable increases in urban ppulatins with high rates f injecting drug use r STDs. Up t ne-third f new HIV infectins in sme urban centres in Sctland are nw due t hetersexual transmissin. Amng wmen attending antenatal clinics in Lndn during 1992, HIV prevalence ranged between I and 5 per Similar surveys f wmen attending antenatal clinics in the USA gave a natinwide figure f 1.7 per 1000.

11 WHO/GPA/CNP/EV M3.1 Page 8 In many large cities f Australasia, Nrth America and Western Eurpe, AIDS has becme a majr cause f death in yung adults aged years. By 1988, AIDS was the leading cause f death amng bth men and wmen aged in New Yrk City, fr example. Latin America and the Caribbean Extensive spread f HIV began in this regin during the late 1970s r early 1980s. In Latin America, mst infectins were initially amng hmsexual r bisexual men. Since the mid 1980s, there has been increasing hetersexual transmissin, principally amng bisexual men and their female sex partners, and amng female sex wrkers and their clients. Fr example, in Brazil the percentage f reprted AIDS cases due t hetersexual transmissin increased frm 7.5% in 1987 t 23% in HIV infectins amng injecting drug users are a grwing prblem, fr example in Argentina (where prevalence ranges frm 30% t 50% ) and. Brazil (20% t 60% ). In mst f the Caribbean, hetersexual transmissin has been the predminant mde f transmissin fr at least a decade. Results frm HIV sentinel surveillance amng peple attending selected STD clinics suggest-,that between 2% and 14% may be infected in different parts f the regin (Figure 3). In-additin, studies amng pregnant wmen attending antenatal clinics in fund HIV prevalences f 2.9% in the Bahamas, and 1.3% in Sant Dming, Dminican Republic, and sa Paul state, Brazil. Further indicatin f the spread f the pandemic in this regin is prvided by studies cnducted in 1991 indicating a prevalence f 0.6% in plice emplyees in Guatemala City and f 0.2% amng bld dnrs in Tegucigalpa, the capital city f Hnduras. As f mid 1993, WHO estimates that 1.5 millin cumulative adult HIV infectins have ccurred in Latin America and the Caribbean (Table I ). WHO als estimates that ver AIDS cases have ccurred in this regin. As f January 1993, mre than adult and paediatric AIDS cases had actually been reprted. By December 1992, Clmbia and Venezuela taken tgether had reprted ver 5000 cumulative AIDS cases, while Argentina had reprted clse t 2000 cases. The number f AIDS cases, and the resulting burden n health care, is highest in Brazil, which had ver reprted cases as f December 1992.

12 WHO/GPA/CNP/EV AN3.1 Page 9 Figure 3. HIV prevalence in STD clinic attenders -Latin America and the Caribbean, Percent HIV-psitive Kingstn. Jamaica Prt Alegre, Brazil Prt f Spain. Trinidad/Tbag San Pedr Sula, Hnduras Sub-Saharan Africa Mst f the available epidemilgical data indicate that the extensive spread f HIV started in sub-saharan Africa in the late 1970s. In sme ppulatins the relatively high rates at which new sexual relatinships are entered int, cmbined with high levels f cnventinal STDs, are believed t be imprtant factrs in hetersexual HIV transmissin. As f mid 1993, WHO estimates that ver 8 millin adult HIV infectins have ccurred in sub-saharan Africa (Table I ). Of this ttal, abut half t tw-thirds have been in East and Central Africa, an area which accunts fr nly abut ne-sixth f the ttal ppulatin f the sub-saharan regin.

13 WHO/GPA/CNP/EV AN3.1 Page 10 At the beginning f 1993, arund cumulative adult and padiatric AIDS cases had been reprted in sub-saharan Africa; hwever, in view f extensive under-diagnsis, under-reprting and reprting delays, WHO estimates that mre than 1.5 millin AIDS cases had ccurred in this regin as f mid 1993, cnstituting ver tw-thirds f the current glbal ttal (Table 1; Figure 2). Because hetersexual transmissin is predminant, the number f HIV infectins in men and wmen are mre r less equal, with females utnumbering males by 6 t 5. Thus, ver 4 millin wmen f childbearing age have been infected. Perinatal transmissin is a widespread and increasing prblem. As f late 1992, WHO estimates that there have been clse t AIDS cases in children. In this regin, transmissin thrugh the transfusin f HIV -infected bld cntinues t accunt fr a relatively small prprtin f ttal HIV infectins -prbably less than 10%. The incidence f HIV transmissin thrugh this rute is declining as rutine HIV screening f bld dnated fr transfusins, and the mre ratinal use f bld, are implemented mre widely. Practices such as ritual scarificatin and the use f inadequately sterilized skin-piercing instruments (e.g., needles and syringes) are believed t accunt verall fr nly a small prprtin f all HIV infectins in sub-saharan Africa. Recent serlgical data frm sub-saharan Africa indicate that the pandemic has cntinued t evlve, particularly in western and suthern Africa (Figure 4). In Zimbabwe alne, fr example, it is estimated that ver peple have been infected. HIV prevalences f ver 18% have been bserved amng adults in the majr urban areas f Btswana. In West Africa, the 1992 results f sentinel surveillance frm Nigeria, a cuntry with almst ne-fifth f sub-saharan A.frica' s ppulatin, clearly indicate that HIV has spread thrughut the cuntry. HIV prevalences f 15% t 20% were fund amng sme grups f female sex wrkers. In 9 f the 11 states in which sentinel surveillance has been instituted amng peple attending STD clinics, prevalence ranged frm 0.5% t 22.1 %. Amng pregnant wmen, HIV prevalence estimates were as high as 5.8% in the same 11 states. In Abidjan, Cte d'ivire, HIV prevalence is 10% t 12%.

14 WHO/GPA/CNP/EV 3.1 Page II Figure 4. Distributin f estimated cumulative HIV infectins in adults -Africa, 1992 Suth and Suth-East Asia Althugh the extensive spread f HIV in Suth and Suth-East Asia began nly in the mid 1980s r even later, the prgressin f the pandemic in this regin has been rapid. As f mid 1993, WHO estimates that ver 1.5 millin HIV infectins have ccurred in adults (Table I). While India and Thailand accunt fr the majrity f reprted infectins, rapid HIV spread int specific ppulatins has been seen elsewhere in the regin. An estimated cumulative AIDS cases in adults and children are believed t have ccurred t date, but nly 1445 cases have been reprted (Table 1 ). In Yunnan Prvince, China, 10% t 30% f injecting drug users have been fund t be infected with HIV. In ther cuntries f the regin there has been a dramatic increase in HIV prevalence amng injecting drug users, as shwn in Figure 5.

15 WHO/GP A/CNP/EV Al93.1 Page 12 Figure 5. HIV prevalence in injecting drug users -Suth and Suth-East Asia, D fe Hetersexual transmissin f HIV appears t be increasing rapidly in ther vulnerable grups; In Thailand as f late 1991, verall median rates f 21% were seen in female prstitutes, and f 5.6% in peple attending STD clinics..as f early 1992, estimates frm Thai sentinel surveillance studies indicated that HIV prevalence amng pregnant wmen attending antenatal clinics was greater than 1.4% in ver 20 prvinces. In at least 4 prvinces prevalence was mre than 4%, and in ne prvince reached 8.8%. In early 1990, the gvernment f Thailand estimated that there were at least HIV -infected peple in the cuntry.it is estimated that by late 1992 this number had risen t apprximately

16 WHO/GPA/CNP/EV 3.1 Page 13 In Suth Asia, the evidence available suggests that as f early 1993 arund I millin adults had been infected with HIV. Studies f HIV prevalence in female sex wrkers pint t a sharply rising trend in at least tw cities f India. A study amng STD patients in Pune, West India, fund an HIV prevalence f almst 9% in 1991 and 17% in As f March 1992, HIV prevalence amng bld dnrs ranged frm 0.1% t 1.8% in fur cities f nrthern, nrtheastern, suthern and western India. * * * The magnitude f the HIV/AIDS pandemic and the relative imprtance f the different rutes f transmissin are nt, as yet, fully established in the fllwing regins: East Asia and the Pacific; Eastern Eurpe and Central Asia; Nrth Africa and the Middle East. Hwever, significant fci f HIV spread have been reprted frm several areas within these regins since the mid 1980s. Apprximately AIDS cases are estimated t have ccurred amng men, wmen and children in these parts f the wrld t date; almst 5000 have been reprted. East Asia and the Pacific WHO estimates that ver cumulative adult HIV infectins had cculted in this regin by late 1992 (Table I). The limited data available indicate that the 663 cumulative AIDS cases reprted as f January 1993 represent reasnably accurately the current status f the pandemic in mst f East Asia and the Pacific. A large prprtin f these AIDS cases were peple with haemphilia wh were transfused with HIV -infected bld prducts in the early t mid 1980s. Yunnan Prvince, China, is gegraphically cntiguus with Suth-East Asia, and the utbreak f HIV infectins amng injecting drug users in that prvince may be cnsidered part f the epidemic in Suth-East Asia. The likelihd f further spread int adjining Guangxi and Guangdng Prvinces f China, as well as int Hng Kng, remains f great cncern. Eastern Eurpe and Central Asia In tw cuntries, lcalized utbreaks f HIV transmissin have ccurred in infants and yung children as a result f unsafe medical practices. In the Kalmykia (Russian Federatin} utbreak, several hundred children were infected thrugh injectins f medicines using shared syringes that had been cntaminated with HIV -infected bld. In the Rmanian utbreak, in

17 WHO/GP A/CNP/EV AI4J3.1 Page 14 which it is believed between 1000 and 2000 children were invlved, transmissin ccurred thrugh transfusins f unscreened bld, and pssibly as a result f the use f needles and/r syringes that had nt been prperly disinfected r sterilized. Hwever, there is n reasn t believe that these are the main rutes f HIV transmissin in this regin. As in ther regins, sexual transmissin is prbably the predminant rute. As f mid 1993, WHO estimates that there have been abut cumulative HIV infectins in adults in Eastern Eurpe and Central Asia (Table I ). Mre than 3000 cumulative adult and paediatric AIDS cases are estimated by WHO t have ccurred in this regin, 2850 having been reprted. HJV prevalence levels amng injecting drug users f at least 10% have been reprted in Pland since Hwever, few ther epidemilgical studies f injecting drug users have been reprted, and the magnitude f the HIV/AIDS prblem in this ppulatin in Eastern Eurpe and Central Asia remains prly defined. Nrth Africa and the Middle East The few studies which are available regarding this regin suggest that the extensive spread f HIV began in sme parts f Nrth Africa and the Middle East in the late 1980s. As f mid 1993, WHO estimates that mre than cumulative adult HN infectins have ccurred in Nrth Africa and the Middle East (Table I ). An HN prevalence as high as 40% has been fund amng female sex wrkers in suthern Sudan and Djibuti, bth f which are part f the HIV / AIDS epidemic in sub-saharan Africa. Only limited and indirect infnnatin is available regarding the extent f high-risk behaviurs in Nrth Africa and the Middle East. Fr example, reprts have suggested substantial numbers f STDs amng the emplyees f sme il cmpanies. Substantial trade in drugs such as herin als appears t ccur in sme parts f the regin. An HIV prevalence f ver 1% was fund in 1989 amng female sex wrkers detained by plice in ne Nrth African cuntry.an HIV prevalence f abut 14% was reprted amng injecting drug users knwn t plice authrities in ne Gulf state in Of the apprximately 1500 HIV infectins amng resident and immigrant expatriates reprted ver the past seven years in anther Gulf state, ne-third were believed t have ccurred during 1992 alne, indicating the rapid evlutin f the epidemic in the regin.

18 WHO/GPA/CNP/EV 3.1 Page 15 III. Glbal estimates and prjectins f HIV/AIDS Uncertainties abut the ptential spread f HIV and the ultimate dimensins f the HIV / AIDS pandemic have existed since the initial recgnitin f AIDS in the early 1980s. The majr uncertainties include: when, and at what level, HIV prevalence will peak in different ppulatins at risk in the varius gegraphical areas, and the rate at which HIV -infected children and adults will ultimately develp AIDS and die. Desp:ite thse uncertainties, a variety f methds and mdels have been develped fr making future prjectins f the pandemic. The first st.ep in making future prjectins is t gauge the current magnitude f the HIV pandemic. Here, the majr prblem is that HIV infectin is largely silent -AIDS cases are the nly visible part f the HIV "iceberg". Attempting t estimate the number f HIV infectins frm (h.e number f AIDS cases has several majr disadvantages. T begin with, the number f AIDS cases may itself be seriusly underestimated in sme cuntries because f inadequate diagnstic facilities and pr reprting mechanisms. Even if the true number f AIDS cases were knwn, estimating the number f HIV infectins frm this number is fraught with difficulty because f the lng and variable time between initial HIV infectin and the nset f AIDS,$ymptms. Mrever, because f the lng interval between infectin and illness, AIDS cases at best reflect the level and distributin f HIV infectin 5-10 years earlier. In making estimates f the cucrent magnitude f HIV spread, WHO therefre draws n ther surces f infrmatin, such as studies f HIV prevalence in specific ppulatin grups and areas, the estimated size f such grups, prevalence in neighburing areas, and trends ver time, fr example the changes in prevalence frm year t year in a given grup (see Figure 5). WHO's estimates f cumulative HIV infectins in adults, and f cucrent and prjected HIV prevalence by "macr" regin, are shwn in Tables 1 and 2 respectively. The ultimate lng-tenn dimensins f the HIV/AIDS pandemic cannt yet be frecast with any degree f cnfidence. Hwever, n the basis f available data n the current glbal status f the pandemic and recent trends in its spread, WHO has generated a plausible range f prjected new HIV infectins during the 1990s. In making prjectins f the future magnitude f the pandemic, WHO uses the lwer limits f its estimated reginal ranges f HIV prevalence. The results f HIV/AIDS frecasting by WHO shuld thus be cnsidered cnservative. During this decade, WHO prjects that arund millin new HIV

19 WHO/GPA/CNP/EV 3.1 Page 16 infectins may be expected in adults, mstly in develping cuntries. During the same perid, WHO prjects that as many as 5-10 millin children will be HIV -infected at birth r thrugh breast-feeding, the majrity f them in sub-saharan Africa. By the year 2000, the cumulative number f HIV -related deaths in adults is predicted t rise t mre than 8 millin frm its current ttal f 2 millin. PrjectIns f the number f AIDS cases in infants and children are based n perinatal transmissin rates f abut 30%. This means that up t 70% f infants brn t HIV -infected mthers will nt be infected. Hwever, because their infected mthers are likely t die f AIDS within 5 t 10 years f their birth, these uninfected infants will cnstitute a grwing ppulatin f rphans. Already as many as 5-10 millin children under 10 years f age will be rphaned by the end f the 1990s as a result f the AIDS-related deaths f their mthers, r bth parents. The number f rphans will increase further in the early years f the next century as a result f the death f thse parents infected with HIV in the 1990s. Fr the year 2000, the current WHO prjectin is that there will be a cumulative ttal f millin HIV infectins in men, wmen and children, f which mre than 90% will be in the develping cuntries. The prjected cumulative ttal f adult AIDS cases is clse t 10 millin. Table 2 shws WHO's estimates, by "macr'l regin, f the number f adults infected with HIV as f mid 1993, and its prjectins f the number wh will be living with HIV infectin in the year Figure 6 illustrates estimated and prjected annual AIDS incidences in the same regins. Table 2. Estimated and prjected HIV prevalence in adults by II macr II regin 'tal number f HIV -infected peple currently alive.

20 Figure 6. Estimated and prjected annual AIDS incidencesl by "macr" regin The increased mrtality amng adults and children has raised cncerns that AIDS may becme s devastating as t reverse psitive ppulatin grwth rates and wipe ut entire ppulatins. In December 1989, WHO, in cnjunctin with the United Natins Ppulatin Divisin, used six mathematical mdels t examine the demgraphic cnsequences f the AIDS pandeic. In a ppulatin with a 3% grwth rate, mdelling shwed that a negative grwth rate wuld result nly when HIV prevalence in the entire ppulatin exceeded 40% -a level that has nt, thus far, been seen in any general ppulatin. During the 1990s, the impact f AIDS will be greatest in large urban areas f sub- Saharan Africa, especially in Eastern and Central Africa, where tday, in sme cities, as many as a quarter t ne-third f all adults aged are infected with HIV. In such cities, AIDS deaths in yung children and in thse aged may reduce expected ppulatin grwth by ver 30%, and the adult mrtality rate may mre than triple. In additin, the ptential exists fr the devastating spread f the pandemic thrughut Asia -a cntinent in which ver half f the wrld's ppulatin live. ******