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Biomedical subjects

K E Nelson

Publications and source records attributed to K E Nelson.

At least 91 records · Page 5Linked to original sources
PubMed1997

The molecular epidemiology of HIV-1 among male sex workers in northern Thailand.

Male commercial sex workers (CSWs) in northern Thailand are at high risk for HIV-1 infection and may be exposed to multiple subtypes of HIV-1 through sexual contact with men and women from Thailand, other Asian nations, and the West. We studied 103 male Thai nationals working in gay bars and clubs in Chiang Mai city who participated in the 1994 sentinel surveillance of the Thai Ministry of Public Health using HIV serologic testing, DNA polymerase chain reaction methods, molecular cloning, differential colony hybridization, nucleotide sequencing, and a third hypervariable region (V3) peptide enzyme-linked immunoabsorbent assay to differentiate subjects infected with HIV-1 subtypes B, E, both, or neither. The majority (58%) reported heterosexual orientation, and 35 (34%) were married. Seventeen (16.5%) were HIV infected: 16 (94%) of 17 had HIV-1 subtype E; 1 had HIV-1 subtype B. Two subjects had dually reactive results by molecular techniques but colony hybridization sequencing revealed only HIV-1 subtype E. HIV-1 subtype E appears to be the predominant clade among male CSWs in northern Thailand. This may have important implications for the global kinetics of the HIV epidemic.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Multiple condom use and decreased condom breakage and slippage in Thailand.

There is compelling evidence that male condoms effectively prevent transmission of sexual pathogens, including HIV-1. Condom breakage and slippage reduce this effect. We measured rates of condom slippage and breakage during heterosexual commercial sex in northern Thailand. Of 7,594 condoms examined in 4,734 client visits (5,040 sex acts), breakage was noted in 1.8% of single condom use (49.3% of acts), as compared with 0.2% with two condoms (49% of sex acts), and no breaks with more than two condoms (1.2% of sex acts). These breakage rates declined from 5.9% in a similar 1992 study in which 2.8% of sex acts were with more than one condom used at a time. Slippage occurred in only 0.1% of sex acts. Case-control analysis indicated that multiple clients, younger aged clients, sex after midnight, and high intensity (rough) sex were associated with condom breaks. The decline in breakage may be attributable to greater expertise in condom use by sex workers and clients, in response to the successful Thai national "100% Condom Campaign." Use of more than one condom during sex has been initiated by sex workers and their clients, a community response to condom promotion messages and fears of HIV infection. These data demonstrate the potential of condom use for high efficacy in reducing exposure to HIV-1 and other STDs. If condom use in commercial sex remains high, HIV incidence may decline among Thai men.

Adult↗
PubMed1997

Widely varying HIV prevalence and risk behaviours among the ethnic minority peoples of northern Thailand.

We compared HIV prevalence, risk behaviours, and social and sexual norms among nine ethnic minority (Hilltribe) groups in northern Thailand. Communities were selected on the basis of size, ethnicity, development level and geography. Subjects (15-45 years) were stratified by gender and selected by household using two-stage randomization. Forty volunteers were identified in each of 27 villages. Participation was voluntary and informed consent was obtained. HIV infection status was determined using ELISA and Western Blot on saliva samples. Risks for HIV were measured with structured interviews using local languages. Overall HIV prevalence was 23/1080 (2.13%) with an equal male-female ratio. HIV prevalence rates were: Shan 8.75%, Akha 5.0%, Yao 5.0%, Thin 1.25%, Hmong 0.63%, Lahu 0.63%, Lisu 0.63%, Karen 0, and Pa-Long 0. Sex worker use was an HIV risk for men (p = 0.0001), but injecting drug use was not; for women, having been a sex worker was a significant HIV risk (p < 0.0001). HIV rates, social norms and sexual behaviour varied considerably among ethnic groups, as did attitudes toward commercial sex work and use. HIV prevention needs to target the Shan, Akha, and Yao communities, and to focus on reduction of brothel work and use.

Adolescent↗
PubMed1997

Case-control study of risk factors for Penicillium marneffei infection in human immunodeficiency virus-infected patients in northern Thailand.

A case-control study was done in Chiang Mai, Thailand, comparing risk-related behavior and exposures in 80 incident cases of disseminated Penicillium marneffei infection in patients with AIDS and 160 control patients with AIDS who did not have P. marneffei infection. All subjects were admitted to Chiang Mai University Hospital between December 1993 and October 1995. Cases were younger than controls (16-30 years vs. > 30 years of age; odds ratio [OR] = 2.22; 95% CI, 1.22-4.07). Patients with a recent history of occupational or other exposure to soil, especially during the rainy season (May to October), were more likely to present with P. marneffei infection (OR = 1.91; 95% CI, 1.04-3.52). History of exposure to or consumption of bamboo rats, the only known nonhuman hosts of P. marneffei, was not a risk factor for infection. Our data suggest that recent exposure to a potential environmental reservoir of organisms in the soil may be associated with disseminated P. marneffei infections among patients with AIDS in Northern Thailand.

Adolescent↗
PubMed1997

Hepatitis A among homosexual men and injection drug users: more evidence for vaccination.

As agencies develop guidelines for administering the newly developed hepatitis A virus (HAV) vaccine, information is needed regarding the occurrence of HAV infection in groups putatively at risk for the infection. We tested serum samples from 300 injection drug users (IDUs), 300 homosexual males, and 300 blood donors for the presence of total antibody to HAV (anti-HAV). Anti-HAV was detected in 66% of IDUs, 32% of homosexual males, and 14% of blood donors. Anti-HAV was not significantly associated (P > .10) with high-risk drug-using behaviors but was more prevalent among IDUs with annual incomes of <$5,000 (P = .018). The occurrence of anti-HAV increased among homosexual males as the number of sexual partners increased (P < .001) but was similar to the age-adjusted prevalence (30.6%) estimated for the general United States population. IDUs are at increased risk for HAV infection; however, our data suggest that factors related to low socioeconomic status contribute more to the occurrence of HAV infection among IDUs than does injection drug use. IDUs and persons at risk for injection drug use should receive HAV vaccine.

Baltimore↗
PubMed1997

Persistence and clinical significance of hepatitis G virus infections in injecting drug users.

To assess the persistence of hepatitis G virus (HGV) infection and its association with liver disease, HGV RNA was assessed in the most recent serum sample for 246 long-term injecting drug users (IDUs) and in prior specimens for those found HGV RNA-positive. HGV RNA was detected at the most recent visit in 38 (15.4%). For 31 (82%), HGV RNA was also found at all prior visits occurring a median of 6.1 years earlier. HGV-positive IDUs were younger and had fewer years of drug use, suggesting that HGV RNA had previously been cleared. Serial samples from 29 short-term IDUs were then assessed. HGV RNA was detected in 9 (31%) of 29 short-term IDUs, and 5 (56%) of the 9 HGV infections cleared. No differences were detected in serum levels of liver-related enzymes among HGV RNA-positive and -negative participants (P > .20). HGV infection is not associated with hepatic inflammation. HGV clearance occurs after many acute infections but uncommonly in persons who remain RNA-positive years after exposure.

Adolescent↗
PubMed1997

Syphilis serology in human immunodeficiency virus infection: evidence for false-negative fluorescent treponemal testing.

Injection drug users were assessed serologically for human immunodeficiency virus infection and syphilis every 6 months. Treatment histories were reviewed for any high-titer biologic false-positive (BFP) reactors, that is, persons with rapid plasma reagin (RPR) titers > or = 1:4 and negative results for fluorescent treponemal antibody absorption (FTA-ABS) tests. Selected sera were analyzed further by immunoblotting for the presence of antibodies reactive with specific Treponema pallidum antigens. Of 112 BFP reactors, 35 (31%) had at least one RPR test reactive at a dilution >1:8 while the FTA-ABS test remained nonreactive. Five reactors (4.5%) converted from nonreactive to reactive by FTA-ABS test; 4 (3.6%) were reactive by FTA-ABS tests but later became nonreactive. Antibodies to T. pallidum membrane antigens were detected in some samples that were persistently nonreactive by FTA-ABS test. Serologic patterns over time, along with very high-titer BFP reactions and reactivity with T. pallidum-specific antigens, suggest that some BFP reactions may represent FTA-negative syphilis.

Antibodies, Bacterial↗
PubMed1997

Tn916 transposition in Haemophilus influenzae Rd: preferential insertion into noncoding DNA.

The availability of completely sequenced genomes has created an opportunity for high throughput mutational studies. Using the conjugative transposon Tn916, a pilot project was initiated to determine the efficiency of gene disruption in the first completely sequenced bacterium, Haemophilus influenzae Rd strain KW20. DNA was isolated from Tn916-mutagenized cells, and the point of transposon insertion was determined by inverse PCR, DNA sequencing, and mapping to the wild-type genome sequence. Analysis of the insertion sites at the nucleotide level demonstrated a biased pattern of insertion into regions rich in stretches of A's and T's. Although Tn916 integrated at multiple dispersed positions throughout the chromosome, 9 of 10 insertion events occurred in noncoding, intergenic DNA. It was determined that the intergenic DNA was over 5% more A + T-rich than that of protein coding sequences. This suggests that A + T-rich sequences similar to the Tn916 insertion site would be more likely to reside in the intergenic DNA. In an effort to identify other likely sites for transposon integration, a hidden Markov model of the consensus target insertion site was derived from the Tn916-H. influenzae junction fragments and searched against the entire genome. Eighty percent of the 30 highest-scoring predicted Tn916 target sites were from intergenic, nonprotein-coding regions of the genome. These data support the hypothesis that Tn916 has a marked preference for insertion into noncoding DNA for H. influenzae, suggesting that this mobile element has evolved to minimize disruption of host cell function on integration.

Base Sequence↗
PubMed1997

HIV-related risk factors of blood donors in northern Thailand before and after knowing HIV test results.

BACKGROUND: The epidemic of Human Immunodeficiency Virus (HIV) infection led blood banks to initiate donation deferral criteria based on self-reported risk factors. However little information is available on the differences in reporting risk factors before and after HIV status is known. METHODS: Between April and July 1994, blood donors in a provincial hospital in northern. Thailand were interviewed at the time of donation, about their demographic characteristics and risk factors. All donors had agreed to learn their test results and were called back for post-test counselling and reinterview. RESULTS: HIV-positive blood donors were more likely to change from 'denying' to 'acknowledging' risk factors while HIV-negatives were more likely to change from 'acknowledging' to 'denying'. The differences between risk factors obtained before and after test results were known resulted in stronger, weaker or even opposite risk measures. CONCLUSION: The study results raise questions about the impact of the differences in reporting HIV-related risk factors by the donors on how effective donation deferral criteria can be developed.

Adult↗
PubMed1997

Multiple condom use in commercial sex in Lamphun Province, Thailand: a community-generated STD/HIV prevention strategy.

BACKGROUND AND OBJECTIVE: In an investigation of condom breakage in commercial sex, we found a high proportion of multiple condoms use. This study sought to ascertain the characteristics of brothel-based commercial sex workers (CSWs) and their clients; to identify the decision makers (clients and/or CSWs) active in choosing multiple condom use; and to determine whether there is an implicit hierarchy of condom use negotiation. GOALS: To identify factors associated with multiple condom use in commercial sex and to provide an understanding of how this innovation developed in this setting. STUDY DESIGN: Sixty-seven brothel-based CSWs in Lamphun Province who participated in a study of condom breakage participated in a case-control study of multiple versus single condom use, which determined CSW and client characteristics for evidence of multiple condom use. Interviews and focus groups were used to determine decision making for condom use and the contexts for multiple use. Association between characteristics of CSWs/clients and multiple condom use was analyzed using X2 for trend. RESULTS: No official program encouraged multiple condom use; this appeared to be a community-devised strategy to increase protection from human immunodeficiency virus (HIV) and other sexually transmitted diseases (STDs). CSWs working in daytime brothels had significantly greater multiple condom use than those working in nighttime brothels; mean percentages + SD of multiple simultaneous use were 57.5% + 28.6 and 35.5% + 22.4, respectively (p < 0.001). Day CSWs were older, had more pregnancies, reported higher frequency of STD symptoms and history of pelvic inflammatory disease, and had more clients per day but had a lower number of sex acts per client than night CSWs. Among factors associated with multiple condoms, only age was significant. The decision to use single or multiple condoms for a sex act was primarily (78.2% in single and 79.3% in multiple) made by the CSW herself. The main reason given for multiple condom use was protection from HIV/STD. CONCLUSIONS: There is high compliance between CSWs in Lamphun province and the Ministry of Public Health-sponsored 100% condom use campaign, and CSWs are attempting to further reduce their risks of HIV/STD exposure by using multiple condoms for sex with their clients.

Adult↗
PubMed1997

Incidence and risk factors for hepatitis C among injection drug users in Baltimore, Maryland.

Between 1988 and 1996, the incidence of and risk factors for hepatitis C virus (HCV) infection were studied in a cohort of injection drug users in Baltimore, Maryland. By second-generation antibody testing of stored serum samples, 142 participants were found to be susceptible to HCV at the time they entered the study. After a median follow-up of 6.5 years, 43 participants (30.3%) developed antibodies to HCV (anti-HCV). The overall incidence was 6.4 cases per 100 person-years, but a substantial decline in the annual incidence rate was observed after the first 2 years (1988 to 1990, 13.4/100 person-years; 1991 to 1996, 2.3/100 person-years [P = 0.0001 for trend]). Participants who acknowledged active drug use, especially those who acknowledged frequent use and sharing of drug paraphernalia, were at increased risk of HCV infection. However, high-risk sexual practices were not associated with HCV seroconversion. Efforts to reduce HCV infection must be focused on curbing drug use and especially on the sharing of needles and drug paraphernalia.

Adult↗
PubMed1997

Seroreactivity to hepatitis E virus in areas where the disease is not endemic.

If the occurrence of hepatitis E virus antibody (anti-HEV) in regions where the disease is not endemic represents infection, rates may be greater in high-risk populations and behavioral correlates may reflect recognized transmission modes. Serum samples from 300 homosexual males, 300 injection drug users (IDUs), and 300 blood donors from Baltimore, Md., were tested for anti-HEV by enzyme immunoassay. Anti-HEV was found in an unexpectedly high percentage of homosexual men (15.9%) and IDUs (23.0%). However, anti-HEV was present in a similar proportion of blood donors (21.3%) (P > 0.05), while hepatitis A, B, and C virus antibodies were more prevalent in the high-risk groups (P < 0.001). Among homosexual men, anti-HEV was not significantly correlated with a history of hepatitis, high-risk sexual practices, or sexually transmitted infections, in contrast to hepatitis A and B antibodies. Among IDUs, anti-HEV was not significantly associated with a history of hepatitis or high-risk drug-using practices, as was found with hepatitis C antibodies. In a setting without endemic hepatitis E disease, there was no evidence that anti-HEV reflected subclinical infection. Until the basis for HEV seroreactivity in such areas is elucidated, anti-HEV results should be interpreted with caution.

Hepatitis E↗
PubMed1997

Osteopathic medical considerations of reflex sympathetic dystrophy.

Review of current medical literature reveals little understanding of the physiology underlying the complex signs and symptoms that accompany reflex sympathetic dystrophy (RSD). The author surveyed the osteopathic medical literature and found a significant body of research documenting the physiology of somatic dysfunction. The manifestations of upper thoracic somatic dysfunction are strikingly similar to those of RSD and may offer insight into its heretofore unexplained physiology of this disorder.

Diagnosis, Differential↗
PubMed1996

Human immunodeficiency virus type 1 neutralizing antibody serotyping using serum pools and an infectivity reduction assay.

Classification of human immunodeficiency virus type 1 (HIV-1) by neutralization serotype may be important for the design of active and passive immunization strategies. Neutralizing antibody serotyping is hindered by the lack of standard reagents and assay format, and by the weak activity of many individual sera. To facilitate cross-clade neutralization analysis, we used an infectivity reduction assay (IRA) and selected clade-specific serum (or plasma) pools from subjects infected with clade B and E HIV-1, respectively. Several serum pools were utilized; some were selected for strong neutralizing activity against intraclade viruses and others were derived from conveniently available samples. Against a panel of 51 clade B and E viruses, serum pools displayed strong neutralization of most intraclade viruses and significantly diminished cross-clade neutralization. Results were confirmed against a blinded panel of 20 viruses. The data indicate that the phylogenetic classification of virus subtypes B and E corresponds to two distinct neutralization serotypes. This approach to neutralizing antibody serotyping may be useful in defining the antigenic relationship among viruses from other clades.

Enzyme-Linked Immunosorbent Assay↗
PubMed1996

Measuring HIV-1 incidence in northern Thailand: prospective cohort results and estimates based on early diagnostic tests.

Measuring the incidence of the human immunodeficiency virus (HIV) is of vital importance but can be difficult and costly. We compared HIV-1 incidence measured directly from prospective cohort studies with rates derived from a method using the prevalence of HIV-1 antibody-negative, p24-antigen-positive individuals. Male and female commercial sex workers (CSWs) were enrolled and followed in separate cohort studies in northern Thailand between 1989 and 1994, and HIV incidence was measured by prospective follow-up of individuals seronegative at baseline. In 1991-1992 cross-sectional serosurveys were done among male and female CSWs in the same region; all HIV-1 antibody-negative subjects in these surveys were tested for p24 antigenemia. HIV incidence was estimated using the prevalence of p24 antigen and a model based on the mean duration of p24 antigenemia before HIV antibody detection. The cohort studies showed high initial incidence rates-23.8/100 person-years (PY) among female CSWs and 11.9/100 PY among male CSWs-but poor compliance with prospective follow-up. Subjects lost to follow-up appeared to be at greater risk of HIV seroconversion than those retained. The p24 antigen method estimate among female CSWs, 25.4%/year, was quite similar to the initial incidence rate found in the cohort. The estimate by the p24 antigen method was higher, 19.9%/year, among male CSWs than that measured prospectively. In populations with high rates of HIV transmission and in whom long-term follow-up is incomplete, estimates of incidence using p24 antigen prevalence among antibody-negative subjects can give useful and economical estimates of HIV incidence and allow for estimates of whether the incidence rates are similar in subjects successfully followed and those lost to follow-up.

Adolescent↗
PubMed1996

Changes in sexual behavior and a decline in HIV infection among young men in Thailand.

BACKGROUND: In Thailand the epidemic of human immunodeficiency virus (HIV) infection is of recent origin. Because of the high seroprevalence of HIV among sex workers, the Ministry of Public Health began a program in 1990 and 1991 to promote the use of condoms during commercial sex. We evaluated the effect of this and other programs to prevent HIV infection in Thailand. METHODS: Using direct interviews, we studied five cohorts of 21-year-old men from northern Thailand who were conscripted into the army by a lottery in 1991, 1993, and 1995. In all, 4311 men were tested for HIV antibodies by enzyme-linked immunosorbent assay, with confirmation by Western blot assay. RESULTS: In the 1991 and 1993 cohorts, the prevalence of HIV infection was 10.4 to 12.5 percent. In 1995, it fell to 6.7 percent (P < 0.001). The seroprevalence was only 0.7 percent among men who did not have sexual relations with a sex worker before 1992. Over the study period, the proportion of men who reported having sexual relations with a sex worker fell from 81.4 percent to 63.8 percent (P < 0.001). From 1991 to 1995, the men's reported use of condoms during the most recent sexual contacts with sex workers increased from 61.0 percent to 92.5 percent (P < 0.001); and in 1995, 15.2 percent of men had a history of a sexually transmitted disease, as compared with 42.2 percent in 1991 (P < 0.001). CONCLUSIONS: Public health programs in Thailand have led to substantial changes in sexual behavior among young men, especially an increased use of condoms, and the rate of new HIV infections has declined.

Adult↗