Disease Progression and Survival with Human Immunodeficiency Virus Type 1
Subtype E Infection among Female Sex Workers in Thailand
Peter H. Kilmarx,1,5Khanchit Limpakarnjanarat,1
Jaranit Kaewkungwal,1,2Renu Srismith,3
Supachai Saisorn,4Wat Uthaivoravit,3
Nancy L. Young,1,5and Timothy D. Mastro1,5
1The HIV/AIDS Collaboration, Nonthaburi,
Medicine, Mahidol University, Bangkok, and
5National Center for HIV, STD, and TB Prevention, Centers
for Disease Control and Prevention, Atlanta, Georgia
2Faculty of Tropical
3Chiang Rai Hospital
4Chiang Rai Provincial Health Office, Chiang Rai, Thailand;
This study describes rates and correlates of disease progression and survival among 194
female sex workers in northern Thailand who were infected with human immunodeficiency
virus type 1 (HIV-1; 96% with subtype E). The median rate of CD4 T lymphocyte decline (3.9
cells/mL/month), median time from infection to !200 CD4 T lymphocytes/mL (6.9 years), and
time to 25% mortality (6.0 years) were similar to those found in studies performed in Western
countries before highly active antiretroviral therapy was available to populations infectedwith
HIV-1 subtype B. Mortality rates among women with 1100,000 HIV-1 RNA copies/mL were
15.4 times higher (95% confidence interval, 5.2–45.2) than among women with !10,000 copies.
Initial CD4 T lymphocyte counts and serum virus load were independently strong predictors
of survival. These results can help in assessing the effects of the epidemic in Thailand and in
determining the prognoses for individual patients.
Rates of disease progression and survival in individuals with
human immunodeficiency virus (HIV) type 1 infection must be
known in order to determine patient prognosis and to assess
the demographic, economic, and social effects of the epidemic.
Most information about disease progression comes from de-
veloped countries [1–14] or from Africa [15, 16]. HIV infection
was not widespread in Asia until the late 1980s, so, although
16.7 million persons in South and Southeast Asia are living
with HIV , there are few studies on HIV disease progression
from the region [18–20]. Population-specific rates areimportant
because geographic areas may differ as a result of factors such
as the availability of treatment and the presence of other in-
fectious diseases, such as tuberculosis [15, 18–20] or penicilliosis
. In addition, although most of the limited data do not
Received 12 November 1999; revised 31 January 2000; electronicallypub-
lished 8 May 2000.
Presented in part: 12th World AIDS Conference, Geneva, Switzerland,
June-July 1998 (abstract 13135).
Written informed consent was obtained from each study participant.The
study protocol was approved by the Ethical Review Committee of the Thai
Ministry of Public Health and by an institutional review board of the US
Centers for Disease Control and Prevention.
Financial support: US Centers for Disease Control and Prevention (as
part of a research collaboration with the Ministry of Public Health of
Use of trade names is for identification purposes only and does not imply
endorsement by the US Department of Health and Human Services or the
Public Health Service or the Ministry of Public Health of Thailand.
Reprints or correspondence: Dr. Peter Kilmarx, The HIV/AIDS Collab-
oration, DMS 6 Bldg., Ministry of Public Health, Tivanon Rd.,Nonthaburi
11000, Thailand (firstname.lastname@example.org).
The Journal of Infectious Diseases
? 2000 by the Infectious Diseases Society of America. All rights reserved.
indicate subtype differences in pathogenesis, infecting HIV-1
viral subtype may also be a factor [16, 22–25].
The quantity of virus in the peripheral circulation has
emerged as one of the most important predictors of disease
progression [7, 12]. However, the studies in which this deter-
mination was made were performed in Western countries with
HIV-1 subtype B, and data on virus levels and pathogenesis
from other geographic areas or for other HIV-1 subtypes are
We report on HIV-1 disease progression and survival rates
among women in the Chiang Rai Health Club; these women
are part of an ongoing cohort study of female sex workers
(FSWs) in upper northern Thailand. Typical of heterosexually
transmitted HIV infection in Thailand,subtypeEpredominates
in this population. Northern Thailand was one of the areas
first and most severely affected by the AIDS epidemic in Asia
, and FSWs, along with injection-drug users, were one of
the first groups to exhibit high infection rates .
Materials and Methods
The Chiang Rai Health Club study has been described elsewhere
[27, 28]. In order to be eligible, women needed to be ?16 years
old, have Thai national identification cards, and report current
employment as an FSW in the Chiang Rai province. They were
approached by the study staff in the Chiang Rai provincial sexually
transmitted diseases (STD) clinic, in other district medical clinics
in the province, and at their workplaces. Enrollment took place
from 1991 through 1994, and prevention counseling and condoms
were provided at each study visit. Epidemiologic data were double-
entered and validated. Epi Info, version 6.04 (Centers for Disease
Control and Prevention, Atlanta); Statistical Analysis Software
by guest on October 27, 2015
JID 2000;181 (May)HIV-1 Subtype E Disease Progression, Thailand1599
counts (higher than median, 3.9 cells/mL/month) among 107 human
immunodeficiency virus (HIV)–infected female sex workers in northern
Risk factors for rapid rate of decline in CD4 T lymphocyte
Age at infection, years
Oral contraceptive use
Depot medroxyprogesterone use
Seropositive at enrollment
Virus load, HIV-1 RNA copies/mL
First CD4 count, cells/mL
NOTE. CI, confidence interval.
(SAS), version 6.12 (SAS Institute, Cary, NC); and Stata, version
6.0 (Stata, College Station, TX) were used for data analysis.
Study participants were evaluated at the pro-
vincial STD clinic at baseline and at 3-month follow-up visits. Use
of contraceptives and antiretroviral agents or antimicrobials for
opportunistic infection prophylaxis was ascertained at each study
visit. HIV-infected women were referred totheonlyisoniazid(INH)
tuberculosis prevention program in the province, and information
on INH use was obtained from that clinic. This report includes
data that was obtained through October 1998.
At enrollment and at follow-up visits, se-
rum specimens were collected and screened for HIV antibodies
(until participants were seropositive) using EIA(HIV-1/HIV-2EIA;
Genetic Systems, Redmond, WA) and, if positive, using Western
blot (WB; NovaPath HIV-1 Immunoblot; BioRad Diagnostics
Group, Hercules, CA). HIV-1 envelope (env) subtype was deter-
mined for seropositive specimens with subtype E and B’ (Thai B)
V-3 loop peptide EIAs (PEIA); nucleic acid sequencing of the C2-
V3 env region was performed on PEIA-nonreactive specimens .
Serum specimens were stored at ?70?C. In 1998 they were tested
for serum HIV-1 RNA virus levels (Amplicor HIV-1 Monitor Test,
version 1.5; Roche Molecular Systems, Branchburg, NJ). In this
test, a new primer pair enhances the ability to amplify non–B sub-
types, allowing for improved HIV-1 RNA detection and quanti-
tation of the subtype E specimens found in Thailand . An en-
rollment specimen was used for women who were seropositive at
enrollment. Because RNA levels stabilize about 6 months after
infection , for the women who seroconverted, we used the first
specimen collected 180 days after the first positive EIA and WB
specimen. If no specimen was available after 180 days, we used the
latest available specimen. CD4 T lymphocytecountwasdetermined
every 3 months for the HIV-seropositive participants. A complete
blood count quantitative buffy-coat analysis (QBC; Centrifugal
Hematology System; Becton Dickinson, Franklin Lakes, NJ) of an
EDTA blood specimen was performed at the Chiang Rai field
station. Another EDTA specimen collected at the same time was
sent on the day of collection via overnight express (in a wet-ice
temperature-controlled cooler) for lymphocyte immunophenotyp-
ing by flow cytometry (FACScan; Becton Dickinson Immunoflow-
cytometry Systems, San Jose, CA), which was performed the fol-
lowing day at the HIV/AIDS Collaboration Laboratory in
Nonthaburi (a suburb of Bangkok, Thailand).
Ascertaining vital status.
Vital status was determinedbyseveral
redundant mechanisms. Study staff learned of patient deaths from
coworkers and family members of the participants. They also re-
viewed records at the provincial public hospital and mortality re-
port forms from the provincial public health office. In Thailand,
deaths are noted in Ministry of Interior districthousingregistration
records and are reported to the national office. From December
1997 through March 1998, study staff reviewed the housing regi-
stration records of all participants registered in Chiang Rai prov-
ince. In December 1998, the Ministry of Interior database was
queried with regard to all 500 women by using the women’s unique
13-digit national identification number. A copy of the mortality
report form was requested for all reported cases of death, andcause
and date of death were abstracted from this report.
Time of infection.
For women who seroconverted, infection
was assumed to have occurred at the midpoint between the last
negative and first positive EIA and WB test results. For women
who were seropositive at enrollment, we made several assumptions,
based on the unique dynamics of the Thai epidemic, about the
timing of infection. HIV infection was introduced in Thailand
shortly before this study began, and it spread very rapidly. The
seroprevalence among brothel-based sex workers in Chiang Rai
increased from 0% in 1987, to 0.5% in 1988, to 46% in 1989, and
then to 60% in 1990 . In addition, infection rates were much
higher among FSWs (32% at enrollment in this cohort), compared
with women of reproductive age in general (3%–6% among preg-
nant women in Chiang Rai during 1991–1994) . Therefore,
infection was assumed to have occurred after a woman began com-
mercial sex work. Finally, in this cohort [27, 28] and in otherstudies
of Thai FSWs , HIV infection was more likely to occur shortly
after the beginning of commercial sex work, so we assumed that
infection occurred relatively close to that time. Women who began
sex work during or before 1987 were assumed to have been infected
in 1989, and those who began during 1988 were assumed to have
been infected in 1990. For women who began sex work during or
after 1989, we assumed that they were infected 1 year after they
began sex work. A woman who began sex work at her current age
or 1 year earlier was assumed to have been infected6 monthsbefore
enrollment. We also did a sensitivity analysis of the effect of our
assumptions on rates of disease progression and survival by using
early and late extreme assumptions about the time of infection
among women who were HIV seropositive at enrollment.
by guest on October 27, 2015
1606 Kilmarx et al. JID 2000;181 (May)
24. Amornkul PN, Tansuphasawadikul S, Limpakarnjanarat K, et al. Clinical
disease associated with HIV-1 subtype B’ and E infection among 2104
patients in Thailand. AIDS 1999;13:1963–9.
25. Alaeus A, Lidman K, Bjorkman A, et al. Similar rate of disease progression
among individuals infected with HIV-1 genetic subtypes A–D. AIDS
26. Weniger BG, Limpakarnjanarat K, Ungchusak K, et al. The epidemiology
of HIV infection and AIDS in Thailand. AIDS 1991;5(Suppl 2):S71–85.
27. Limpakarnjanarat K, Mastro TD, Saisorn S, et al. HIV-1 and other sexually
transmitted infections in a cohort of female sex workers in Chiang Rai,
Thailand. Sex Transm Infect 1999;75:30–35.
28. Kilmarx PH, Limpakarnjanarat K, Mastro TD, et al. HIV-1 seroconversion
in a prospective study of female sex workers in northern Thailand: con-
tinued high incidence among brothel-based women. AIDS 1998;12:
29. Subbarao S, Limpakarnjanarat K, Mastro TD, et al. HIV-1 in Thailand,
1994–1995: persistence of two subtypes with low genetic diversity. AIDS
Res Hum Retroviruses 1998;14:319–27.
30. Parekh B, Phillips S, Granade TC, Baggs J, Hu DJ, Respess R. Impact of
HIV type 1 subtype variation on viral RNA quantitation. AIDS ResHum
31. Bunnell RE, Yanpaisarn S, Kilmarx PH, et al. HIV-1 seroprevalence among
childbearing women in northern Thailand: monitoring a rapidly evolving
epidemic. AIDS 1999;13:509–15.
32. Ungchusak K, Rehle T, Thammapornpilap P, Spiegelman D, Brinkmann U,
Siraprapasiri T. Determinants of HIV infection among femalecommercial
sex workers in northeastern Thailand: results from a longitudinal study.
J Acquir Immune Defic Syndr Hum Retrovirol 1996;12:500–7.
33. Webster HK, Pattanapanyasat K, Pjanupak P, et al. Lymphocyte immuno-
phenotype reference ranges in healthy Thai adults: implications for man-
agement of HIV/AIDS in Thailand. Southeast Asian J Trop Med Public
34. Centers for Disease Control and Prevention. 1993 reised classificationsystem
for HIV infection and expanded surveillance case definition for AIDS
among adolescents and adults. MMWR Morb Mortal Wkly Rep 1992;
35. Karon JM, Buehler JW, Byers RH, et al. Projections of the number ofpersons
diagnosed with AIDS and the number of immunosuppressedHIV-infected
persons, United States, 1992–1994. MMWR Morb Mortal Wkly Rep
36. Tansuphasawadikul S, Amornkul PN, Tanchanpong C, et al. Clinical pre-
sentation of hospitalized adult patients with HIV infection and AIDS in
Bangkok, Thailand. J Acquir Immune Defic Syndr 1999;21:326–32.
37. Veugelers PJ, Schechter MT, Tindall B, et al. Differences in time from HIV
seroconversion to CD4?lymphocyte end-points and AIDS in cohorts of
homosexual men. AIDS 1993;7:1325–9.
38. Evans JS, Nims T, Cooley J, et al. Serum levels of virus burden in early-
stage human immunodeficiency virus type 1 disease in women. J Infect
39. Pape JW, Jean SS, Ho JL, Hafner A, Johnson WD Jr. Effect of isoniazid
prophylaxis on incidence of active tuberculosis and progression of HIV
infection. Lancet 1993;342:268–72.
40. Wiktor SZ, Sassan-Morokro M, Grant AD, et al. Efficacy of trimethoprim-
sulphamethoxazole prophylaxis to decrease morbidity and mortality in
HIV-1–infected patients with tuberculosis in Abidjan, Co ˆte d’Ivoire: a
randomised controlled trial. Lancet 1999;353:1463–75.
41. van Benthem BHB, Veugelers PJ, Schechter MT, Kaldor JM, Page-Shafter
KA, van Griensven GJP. Modelling the AIDS incubation time:evaluation
of three right censoring strategies. AIDS 1997;11:834–5.
42. Ngamvithayapong J, Uthaivoravit W,YanaiH, AkarasewiP,Sawanpanyalert
P. Adherence to tuberculosis preventive therapy among HIV-infected per-
sons in Chiang Rai, Thailand. AIDS 1997;11:107–12.
43. Furth PA, Westphal H, Hennighausen L. Expression from the HIV-LTR is
stimulated by glucocorticoids and pregnancy. AIDS Res Hum Retrovi-
44. Biggar RJ, Pahwa S, Minkoff H, et al. Immunosuppression in pregnant
women infected with human immunodeficiency virus. Am J Obstet Gy-
45. Weisser M, Rudin C, Battegay M, et al. Does pregnancy influence the course
of HIV infection? J Acquir Immune Defic Syndr Hum Retrovirol 1998;
46. Clark RA, Bessinger R. Clinical manifestations and predictors of survival in
older women infected with HIV. J Acquir Immune Defic Syndr Hum
47. Alcabes P, PezzottiP,PhillipsAN,RezzaG,VlahovD.Long-termperspective
on the prevalent-cohort biasesinstudiesofhumanimmunodeficiencyvirus
progression. Am J Epidemiol 1997;146:543–51.
48. Surasiengsunk S, Kiranandana S, Wongboonsin K, Garnett GP, Anderson
RM, van Griensven GJP. Demographic impact of the HIV epidemic in
Thailand. AIDS 1998;12775–84.
by guest on October 27, 2015