Lights, camera research! Short film and social media to recruit to HIV research in Indonesia.

Introduction: HIV prevalence among men who have sex with men has increased in Indonesia, amid reports of growing stigma against lesbian, gay, bisexual and transgender individuals and policies that have pushed back public health outreach to these groups. Methods: We assessed the utility of tailored short film and targeted social media engagement to recruit men who have sex with men in Indonesia to HIV social science research. A short HIV testing promotion film, anonymised short survey and invite to a wider research study was embedded on a website platform and disseminated using geo and social/community group targeting for 1 month via a social networking app and social media platforms. Results: From 3 January 2021 to 3 February 2021, there were over 2200 hits of the website within Indonesia. A total of 177 male web users who identified as men who have sex with men or preferred not to declare their sexuality, engaged by watching the short film and completing the survey, they were aged between 17 and 60 years old, of Indonesian nationality and living in Indonesia. Of these, 88% indicated having at least one HIV test in their lifetime, 66% had felt shame with respect to their sexuality and 53% indicated feeling afraid to have a HIV test. Ninety (51%) of the 177 validated using their email or mobile phone number demonstrating willingness to be contacted to join a further study. Twenty-three eligible men who have sex with men, aged 21-55 years old, joined a further social science research study. Participants were from diverse backgrounds and included men born in provinces outside Bali, of different socio-economic and employment backgrounds and diverse relationship contexts. Discussion: Engaging, empowering digital media involving key health messaging can provide health education in more effective ways, build trust and bring communities together. Targeted digital and social media approaches could reach increasingly marginalised and vulnerable communities to promote individual and public health and enable recruitment to valuable medical research.

Phylogenetic analysis and victim contact tracing of rabies virus from humans and dogs in Bali, Indonesia.

SUMMARY: The emergence of human and animal rabies in Bali since November 2008 has attracted local, national and international interest. The potential origin and time of introduction of rabies virus to Bali is described. The nucleoprotein (N) gene of rabies virus from dog brain and human clinical specimens was sequenced using an automated DNA sequencer. Phylogenetic inference with Bayesian Markov Chain Monte Carlo (MCMC) analysis using the Bayesian Evolutionary Analysis by Sampling Trees (BEAST) v. 1.7.5 software confirmed that the outbreak of rabies in Bali was caused by an Indonesian lineage virus following a single introduction. The ancestor of Bali viruses was the descendant of a virus from Kalimantan. Contact tracing showed that the event most likely occurred in early 2008. The introduction of rabies into a large unvaccinated dog population in Bali clearly demonstrates the risk of disease transmission for government agencies and should lead to an increased preparedness and efforts for sustained risk reduction to prevent such events from occurring in future.

Increasing resistance to ciprofloxacin and other antibiotics in Neisseria gonorrhoeae from East Java and Papua, Indonesia, in 2004 - implications for treatment.

We examined gonococci isolated in 2004, in East Java and Papua, Indonesia, to review the suitability of ciprofloxacin-based and other treatment regimens. Gonococci from the two provinces were tested in Sydney for susceptibility to penicillin, tetracycline, spectinomycin, ceftriaxone, ciprofloxacin, gentamicin, azithromycin and rifampicin. Of 163 gonococcal isolates from East Java (91) and Papua (72), 120 (74%) of gonococci, 62 (68%) and 58 (80%) from East Java and Papua, respectively, were penicillinase-producing gonococci and 162 displayed high-level tetracycline resistance. Eighty-seven isolates (53%) were ciprofloxacin resistant, 44 (48%) from East Java and 43 (60%) from Papua. All isolates were sensitive to cefixime/ceftriaxone, spectinomycin and azithromycin. Minimum inhibitory concentrations of gentamicin were in the range 0.05-8 mg/L. Sixty-nine gonococci (42%) showed combined resistance, to penicillin, tetracycline and quinolones. Quinolone resistance has now reached unacceptable levels, and their use for the treatment of gonorrhoea in Indonesia should be reconsidered.

Treatment of tinea imbricata: a randomized clinical trial using griseofulvin, terbinafine, itraconazole and fluconazole.

BACKGROUND: Griseofulvin has been the mainstay of treatment for tinea imbricata (TI) for decades; however, there have been few reports of efficacy of newer antifungals in the treatment of this condition. Many patients with TI have several obstacles to treatment due to their remote geographical locations and the primitive nature of their societies. OBJECTIVES: The aim of this study was to compare the efficacy of itraconazole, terbinafine and fluconazole with that of griseofulvin after 4 weeks of therapy. METHODS: Patients aged 12-76 years with the clinical diagnosis of TI were randomly assigned to one of four treatment groups: griseofulvin 500 mg twice daily for 4 weeks, terbinafine 250 mg daily for 4 weeks, itraconazole 200 mg twice daily for 1 week or fluconazole 200 mg once weekly for 4 weeks. Disease activity was monitored weekly. Laboratory measurements included monitoring complete blood count and liver function enzymes. Fifty-nine patients were included in the efficacy analysis: 13 in the fluconazole group, 15 in the griseofulvin group, 12 in the terbinafine group and 19 in the itraconazole group. RESULTS: Significant remission was achieved in the terbinafine and griseofulvin groups, lasting up to 8 weeks after cessation of therapy. The fluconazole group experienced no significant remission, and remission was of short duration in the itraconazole group. No adverse events were reported, and non-compliance with medications or follow-up was the only reason for removal from the study. CONCLUSIONS: Griseofulvin and terbinafine are effective in the treatment of TI. The decision of whether to treat at all and which medication to choose depends greatly on the extent of involvement, the social situation, and the availability of resources such as laboratory testing and follow-up.

Importation of multiple HIV type 1 strains into West Papua, Indonesia (Irian Jaya).

HIV-1 from 16 sexually transmitted disease clinic patients in Timika, West Papua, Indonesia was amplified by RT-PCR and subtyped by a combination of envelope and gag region heteroduplex mobility analysis (HMA) and direct PCR DNA sequencing. HMA showed the presence of 14 subtype E (CRF01_AE) and 2 subtype B HIV-1. Phylogenetic analysis of a 540-bp V3-V4 region of gp120 showed that 9 of 10 CRF01_AE variants clustered tightly with a median distance of 1.3% (range, 0.5 to 2.2%) whereas 1 CRF01_AE variant diverged significantly from the others (median distance, 10.7%; range, 10.1 to 11.8%). One subtype B virus envelope was typical of United States/European strains whereas the other appeared to be related to Thai subtype B' variants. These results reflect the independent introduction of multiple HIV-1 strains into West Papua, with the rapid spread in the majority of infected patients tested of a single strain of HIV-1E (CRF01_AE).

Asymptomatic sexually transmitted disease prevalence in four military populations: application of DNA amplification assays for Chlamydia and gonorrhea screening.

The prevalence of asymptomatic chlamydial and gonococcal infections in male and female military populations was determined using urine-based ligase chain reaction DNA amplification assays (DAAs). Cross-sectional surveys in four military settings revealed an overall prevalence of asymptomatic chlamydial infection of 4.2% (56/1338). This included 3.4% (21/618) of Western Pacific shipboard US Marine Corps enlisted men; 5.2% (21/406) of male marines shore-based in Okinawa, Japan; 2.7% (5/183) of female enlisted US Navy subtender personnel in dry dock; and 6.9% (9/131) of shore-based female naval personnel in San Diego. No gonococcal infections were detected. All subjects were treated within 2 weeks of screening; none of them had progressed to symptomatic disease. General population-based screening for asymptomatic sexually transmitted diseases, and in particular chlamydial infection, can be successfully implemented using urine-based DAA tests. Benefits are maximized in a population in which compliance for follow-up therapy is high.

Immune response against the exp-1 protein of Plasmodium falciparum results in antibodies that cross-react with human T-cell lymphotropic virus type 1 proteins.

To examine the role of the Plasmodium falciparum Exp-1 blood-stage protein in producing antibodies that cross-react with human T-cell lymphotropic virus type I (HTLV-I) proteins, we studied sera from Indonesian volunteers who seroconverted to malaria after transmigrating to an area where malaria is hyperendemic. Samples from Philippine volunteers, that were used in a prior study that examined malaria antibodies that cross-react with HTLV-I proteins, were also used. Eighty-three percent of the Indonesian transmigrants developed antibodies against the malaria Exp-1 protein by 6 months postmigration. Of these malaria seroconverters, 27% developed false-positive HTLV-I enzyme immunoassay (EIA) immunoreactivity, as indicated by indeterminate HTLV-I Western blot banding patterns. Five of the six Philippine samples tested were HTLV-I EIA false positive and Western blot indeterminate. When a recombinant Exp-1 protein was used in blocking experiments, the HTLV-I Western blot immunoreactivity of sera from both groups was either completely eliminated or greatly reduced. No effect on the Western blot immunoreactivity of truly HTLV-I-positive sera was seen. To determine if immunization with the recombinant Exp-1 protein could elicit the production of HTLV-I antibodies, six mice were inoculated with the recombinant protein. Following administration of three 50-microgram doses of the protein, four of the six mice developed antibodies that cross-reacted with HTLV-I proteins on Western blot. These results indicate that the immune response against the malaria Exp-1 protein may result in HTLV-I-cross-reacting antibodies that can lead to false-positive EIA and indeterminant Western blotting results.

An outbreak of El Tor cholera associated with a tribal funeral in Irian Jaya, Indonesia.

An outbreak of El Tor biotype cholera occurring in a rural village in Irian Jaya, Indonesia was evaluated for risk factors associated with death from cholera. Among those dying in the village during the epidemic, a significant association between membership in one of the five tribal groups in the village complex was associated with an elevated risk of suffering a cholera death (odds ratio = 5.9). Interviews with members of the decedents' families revealed a very strong association (odds ratio = 11.6) between risk of cholera death and having attended the two day funeral of a woman who died of a cholera-like illness a few days prior to an outbreak of cholera-like diarrheal disease in the village complex. Recent flooding may have contributed to the creation of an environment conducive to cholera transmission.

Epidemic and sporadic hepatitis E virus transmission in West Kalimantan (Borneo), Indonesia.

A cross-sectional survey was conducted in West Kalimantan (Borneo), Indonesia to geographically profile hepatitis E virus (HEV) prevalence in the riverine areas recognized as the foci of epidemic HEV transmission in 1987. Additionally, a contiguous, although distinct, population with no identifiable historical exposure to epidemic HEV was surveyed downstream for comparative purposes. Eight hundred eighty-five sera were assayed by enzyme immunoabsorbent assay for anti-HEV IgG and anti-hepatitis A virus (HAV) IgG markers. A very high percent (90%) of both the outbreak and comparison populations was anti-HAV IgG positive by the age of nine years. In contrast, the prevalence of anti-HEV IgG in the outbreak area (50%) was significantly higher than in the comparison area (23%) (P < 0.0001). In both the outbreak and comparison areas, anti-HEV IgG prevalence increased with age ( < 0.0001), except for the group > or = 50 years of age. The prevalence (53%) of antibody to HEV in the population > or = seven years of age from the outbreak area (alive during the actual 1987 outbreak) was significantly (P < 0.0001) greater than among the children < seven years of age (born after the outbreak) (15%). However, anti-HEV IgG prevalence among the population from the comparison area did not differ significantly between the > or = seven- (23%) and < seven- (20%) year-old age groups. The percentage of anti-HEV IgG-positive individuals among males (47%) from the outbreak area was lower (P < 0.05) compared with females (55%). While overall usage of river water for drinking purposes was not universal, dependence on river water as a primary source was significantly higher (P < 0.001) in households from the outbreak area (60%) compared with the comparison area (30%). This study indicates persistence of an anti-HEV IgG response in a large percentage of the population seven years after an epidemic of HEV infections. Also, the relatively high prevalence (15%) of anti-HEV in children < seven years of age from the outbreak area reflects continuing, sporadic infections.

Mefloquine compared with doxycycline for the prophylaxis of malaria in Indonesian soldiers. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: Mefloquine and doxycycline are the two drugs recommended for prophylaxis of malaria for visitors to areas where Plasmodium falciparum is resistant to chloroquine. OBJECTIVE: To compare the efficacy and tolerability of mefloquine with those of doxycycline as prophylaxis for malaria. DESIGN: Randomized, double-blind, placebo-controlled field trial of chemoprophylaxis of malaria. SETTING: Northeastern Irian Jaya, Indonesia. PARTICIPANTS: 204 Indonesian soldiers. INTERVENTION: After radical curative treatment, participants were randomly assigned to receive 100 mg of doxycycline per day and mefloquine placebo; 250 mg of mefloquine per week (preceded by a loading dose of 250 mg/d for 3 days) and doxycycline placebo; or placebos for both drugs. Prophylaxis lasted approximately 13 weeks. MEASUREMENTS: The primary end point for efficacy was the first occurrence of malaria, as documented by a positive malaria smear. Malaria smears were obtained weekly and when patients had symptoms suggesting malaria. Reported symptoms were recorded daily, and an exit study questionnaire was conducted. RESULTS: In the placebo group, 53 of 69 soldiers developed malaria (9.1 person-years), resulting in an attack rate of 5.8 cases per person-year (95% CI, 4.3 to 7.7 cases per person-year). Plasmodium falciparum accounted for 57% of cases, and P. vivax accounted for 43% of cases. No malaria occurred in the 68 soldiers (16.9 person-years) in the mefloquine group; thus, the protective efficacy of mefloquine was 100% (CI, 96% to 100%). In the doxycycline group, P. falciparum malaria occurred in 1 of 67 soldiers (16.0 person-years), yielding a protective efficacy of 99% (CI, 94% to 100%). Both drugs were very well tolerated. CONCLUSIONS: Mefloquine and doxycycline were both highly efficacious and well tolerated as prophylaxis of malaria in Indonesian soldiers.

Diagnosis of resistance to chloroquine by Plasmodium vivax: timing of recurrence and whole blood chloroquine levels.

To develop criteria for the diagnosis of resistance to chloroquine using an in vivo test, we examined published records of early clinical trials of quinine and chloroquine against Plasmodium vivax. These data established the timing of relapse by tropical P. vivax relative to therapy by these drugs. The first relapse occurred 17 days after initiating and three days after terminating quinine therapy. The median day of relapse was day 23, and 59% of the patients had relapsed by day 30 (n = 333). In contrast, no relapse occurred until day 36 following chloroquine treatment (n = 256). Data from our laboratory may help explain this difference; among 91 Indonesian patients with malaria, the mean whole blood levels of chloroquine (CQ) and desethylchloroquine (DCQ) were 141 ng/ml (95% confidence interval = 115-167) on day 28 after initiating standard therapy (25 mg base/kg in three doses over a 48-hr period). This exceeds the estimated minimal effective concentration of chloroquine (100 ng/ml of whole blood). Thus, chloroquine lingering in the blood for at least 28 days after starting standard therapy was sufficient to eliminate or at least suppress chloroquine-sensitive tropical P. vivax. We conclude that a parasitemia by P. vivax recurring in the 28 days after full compliance to standard chloroquine therapy demonstrates resistance. If the recurrence appears before day 16, it is almost certainly a recrudescence and between days 17 and 28 it may be either a recrudescence or a relapse by chloroquine-resistant parasites. Recurrences beyond day 28 could be relapse by chloroquine-sensitive P. vivax.

Systemic reactions in U.S. Marine Corps personnel who received Japanese encephalitis vaccine.

The overall hypersensitivity reaction rate among 14,249 U.S. Marine Corps personnel who received 36,850 doses of an investigational Japanese encephalitis vaccine was 10.3 per 10,000 doses; reaction rates were 16.1 and 10.3 per 10,000 doses for the first two doses, and 2.0 per 10,000 doses for the third. The reaction rate was 26.7 per 10,000 vaccinees. Of 38 reactors, 26 had urticaria and/or angioedema, and 11 had pruritus. Vaccine reaction intervals clustered within 48 hours for dose 1, but the median reaction interval for dose 2 was 96 hours. A history of urticaria or allergic rhinitis was associated with an increased probability of a vaccine reaction.

Malaria in a nonimmune population after extended chloroquine or primaquine prophylaxis.

Extended chemoprophylaxis against endemic malaria raises concern with regard to susceptibility after ceasing use of the drug. In this study, we measured attack rates of malaria among adult men for 28 weeks after they ended one year of prophylaxis using either weekly chloroquine (5 mg base/kg, n = 20), daily primaquine (0.5 mg base/kg, n = 30), or a placebo of primaquine (n = 41). The 28-week incidence densities, times to parasitemia, parasite densities, and symptoms of primary post-prophylaxis infections were not significantly different among the former primaquine, chloroquine, and placebo groups. However, the incidence of Plasmodium falciparum infection in the post-chloroquine group was significantly greater than in the post-primaquine group during the first (P = 0.03) and second (P = 0.02) months post-prophylaxis. Six of 10 primary P. falciparum and three of 10 P. vivax infections occurred in the former chloroquine group within one month after ending prophylaxis and the mean time to infection was 30-35 days. In contrast, only one P. falciparum and no P. vivax infections occurred during the first month after ending primaquine prophylaxis. The mean time to first parasitemia by either species of malaria parasite in this group was 72-77 days. There was no indication that daily use of primaquine for one year placed subjects at greater risk of malaria infection or to more severe clinical symptoms of malaria than subjects who had taken placebo or chloroquine, despite the potential for some degree of immunity to have been acquired in these latter two groups during the year-long prophylaxis period. The results do suggest that chloroquine suppressed P.falciparum infections until drug levels decreased, and that primaquine had effectively prevented the establishment of liver-stage parasites.

Genetic, antigenic and serologic characterization of human immunodeficiency virus type 1 from Indonesia.

To examine the genetic and antigenic characteristics of HIV-1 in Indonesia, samples from 19 HIV-positive volunteers were studied. By a combination of PCR typing and DNA sequence analysis, 12 of the 19 volunteers were determined to be infected with HIV-1 clade B and seven with clade E. Six of the seven Indonesian clade E isolates were from volunteers associated with the Indonesian Military during a peacekeeping mission in Cambodia. Infectivity reduction neutralization assays showed that the Indonesian E viruses were effectively neutralized by Thailand clade E HIV-1 antisera but not by U.S. clade B antisera. The Indonesian clade B virus tested was neutralized by U.S. clade B antisera and not by the Thailand E antisera. Using a previously described serologic typing ELISA based on clade B and E V3 peptides, genetic clade was accurately determined in eight of eight sera tested. This is the first report of the genetic and antigenic analysis of HIV-1 isolates from Indonesia. The data indicate that at least two genetic and antigenic HIV-1 clades (clade E and B) circulate in Indonesia.

The postwar hospitalization experience of U.S. veterans of the Persian Gulf War.

BACKGROUND: Since the Persian Gulf War ended in 1991, many veterans of that conflict have reported diverse, unexplained symptoms. To evaluate the health of Gulf War veterans, we studied their postwar hospitalization experience and compared it with that of other military personnel serving at the same time who did not go to the Persian Gulf. METHODS: Using a retrospective cohort approach and data from Department of Defense hospitals, we studied hospitalizations of 547,076 veterans of the Gulf War who were serving in the Army, Navy, Marine Corps, and Air Force and 618,335 other veterans from the same era who did not serve in the Persian Gulf. Using multivariate logistic-regression models, we analyzed risk factors for hospitalization both overall and in 14 broad diagnostic categories during three periods from August 1991 through September 1993 (a total of 45 specific comparisons). RESULTS: After the war, the overall odds ratio for hospitalization of the Gulf War veterans was not higher than that of the other veterans, even after adjustment for selection effects related to deployment. In 16 of the 42 comparisons involving specific diagnoses, the risk of hospitalization among Gulf War veterans differed significantly from that among other veterans. Among these 16 comparisons, Gulf War veterans were at higher risk in 5: neoplasms (largely benign) during 1991, diseases of the genitourinary system during 1991, diseases of the blood and blood-forming organs (mostly forms of anemia) during 1992, and mental disorders during both 1992 and 1993. The differences were not consistent over time and could be accounted for by deferred care, postwar pregnancies, and postwar stress. CONCLUSIONS: During the two years after the Persian Gulf War, there was no excess of unexplained hospitalization among Americans who remained on active duty after serving in that conflict.

The epidemiology of HIV-1 infection in Peru, 1986-1990.

OBJECTIVE: To determine the extent of the HIV-1 epidemic in Peru. DESIGN: Part of a national serosurvey in Peru. METHODS: Between January 1986 and December 1990, 140,976 serum samples were tested for HIV-1 antibody. RESULTS: HIV-1 antibody was found in a high percentage of serum samples provided by 4300 homosexual men (26%), 2204 male sexually transmitted disease patients (10%), 145 drug users (13%), 269 hemophiliacs (10%), and 146 unlicensed female prostitutes (10%). In addition, the prevalence of HIV-1 infection increased substantially among these groups between the beginning and end of the survey period. A low but rising prevalence of HIV-1 antibody was found during this period among serum samples provided by 83,526 blood donors and 11,101 military personnel:total period prevalence, 0.25 and 0.32%, respectively. CONCLUSION: These data indicate that HIV-1 infection is epidemic in Peru among groups at high risk of sexually and parenterally transmitted diseases, and that the risk of infection appears to be low but possibly increasing among the general population.

PIP: The findings of a national seroprevalence survey conducted in Peru during 1986-90 indicate accelerating rates of human immunodeficiency virus (HIV) among population groups at high risk of sexually transmitted diseases. Two databases were maintained: 1) January 1986-December 1988 and 2) January 1989-December 1990. Of the 140,976 survey participants, 3345 (2.4%) were HIV-positive by Western blot. 2591 participants were selected because of clinical signs suggestive of acquired immunodeficiency syndrome (AIDS); 46.7% were HIV-positive, but the prevalence increased from 19% in the 1986-88 period to 60% during 1989-90. Among the 4300 men who identified themselves as homosexual or bisexual, 26% were seropositive (8% during 1986-88 and 41% during 1989-90). HIV prevalence among 2204 men attending a sexually transmitted diseases clinic was 10.3%, with an increase from 2.0% in the first period to 19.0% in the later period. 10.4% of the 269 hemophiliacs were HIV-infected, with an increase from 8% to 36%. Among the 145 intravenous drug users, the prevalence rose from 1% during 1986-88 to 27% during 1989-90. Among 5827 registered female prostitutes, the prevalence rose from 0.3% to 0.7%; however, a 1990 analysis of 146 unregistered prostitutes revealed a rate of 9.6%. The HIV rates among 285 female and 105 male heterosexual partners of known HIV-positive persons were 50.2% and 40.0%, respectively. HIV prevalence increased from 0.8% during 1986-88 to 8.0% during 1989-90 among 1532 men and 1247 women who requested anonymous HIV testing. The prevalence among 542 male and 615 female medical personnel was 2.3%. Among 78,793 volunteer and 4733 paid blood donors, HIV prevalence was 0.2% (0.3% among paid donors). The period prevalence among 11,101 male military recruits and active duty members increased from 0.009% to 0.5%. Finally, only 0.3% of 21,595 applicants for immigration visas were HIV-positive, and there were no HIV cases among 1234 pregnant women attending antenatal clinics. Although the very low HIV prevalence among military personnel and pregnant women suggests that the virus is not yet widely disseminated within the general population, the finding that 28% of HIV-positive men were married and engaged in bisexual behavior suggests potential for heterosexual transmission in the years ahead.

War syndromes and their evaluation: from the U.S. Civil War to the Persian Gulf War.

PURPOSE: To better understand the health problems of veterans of the Persian Gulf War by analyzing previous war-related illnesses and identifying possible unifying factors. DATA SOURCE: English-language articles and books on war-related illnesses published since 1863 that were located primarily through a manual search of bibliographies. DATA EXTRACTION: Publications were assessed for information on the clinical characteristics of war-related illnesses and the research methods used to evaluate such illnesses. DATA SYNTHESIS: Poorly understood war syndromes have been associated with armed conflicts at least since the U.S. Civil War. Although these syndromes have been characterized by similar symptoms (fatigue, shortness of breath, headache, sleep disturbance, forgetfulness, and impaired concentration), no single recurring illness that is unrelated to psychological stress is apparent. However, many types of illness were found among evaluated veterans, including well-defined medical and psychiatric conditions, acute combat stress reaction, post-traumatic stress disorder, and possibly the chronic fatigue syndrome. No single disease is apparent, but one unifying factor stands out: A unique population was intensely scrutinized after experiencing an exceptional, life-threatening set of exposures. As a result, research efforts to date have been unable to conclusively show causality, have been subject to reporting bias, and have lacked similar control populations. In addition to research limitations, war syndromes have involved fundamental, unanswered questions about the importance of chronic somatic symptoms and the factors that create a personal sense of ill health. CONCLUSION: Until we can better understand what constitutes health and illness in all adult populations, we risk repeated occurrences of unexplained symptoms among veterans after each war.

Survey of resistance to chloroquine by Plasmodium vivax in Indonesia.

In February 1995 we surveyed to chloroquine among patients with Plasmodium vivax malaria at Nias Island, in the Indian Ocean near north-western Sumatra, Indonesa. The subjects, 21 indigenous males and females (6-50 years old) infected with > 40 asexual blood stage parasites of P. vivax per microliter of blood, had mild symptoms or none at all. Seven of these patients had > 100 ng/mL whole blood chloroquine levels before the first supervised dose of chloroquine (3 doses of 10 mg/kg, 10 mg/kg, 5 mg/kg of base given at 24 h intervals). Whole blood chloroquine levels on the last day of dosing confirmed normal absorption (range 413-3248, mean 1141, SD 616 ng/mL). Blood films were examined on days 0, 2, 4, 7, 11, 14, 18, 21 and 28 after initiating therapy. Three patients had recurrent asexual P. vivax parasitaemias between days 14 and 18, despite effective levels of chloroquine in whole blood (> or = 100 ng/mL) at the time of recurrence. Resistance to standard chloroquine therapy by P. vivax appeared in 14% of infections among residents of Nias.