Dengue fever in US military personnel in Haiti.

OBJECTIVE: To describe clinical manifestations and public health implications of an outbreak of dengue fever (DF) during Operation Uphold Democracy, Haiti, 1994. DESIGN: Consecutive sample. SETTING: Military combat support hospital, Port-au-Prince, Haiti. PATIENTS: A total of 101 US military personnel with acute febrile illnesses. INTERVENTIONS: A disease surveillance team collected clinical and epidemiologic data from US military clinics throughout Haiti. Febrile patients admitted to the combat support hospital were evaluated with standardized clinical and laboratory procedures. The surveillance team followed patients daily. MAIN OUTCOME MEASURES: Arbovirus isolation and specific antibody determination and symptoms and physical findings. RESULTS: Febrile illnesses accounted for 103 (25%) of the 406 combat support hospital admissions during the first 6 weeks of deployment. All patients with febrile illness recovered. A total of 30 patients had DF; no patient had evidence of infection with malaria. Dengue virus serotypes 1, 2, and 4 were isolated from 22 patients, and 8 patients developed IgM antibody to dengue virus. Patients with DF could not be distinguished from other febrile patients on clinical grounds alone. No arboviruses other than dengue were identified. CONCLUSIONS: Active surveillance, with clinical and laboratory evaluation directed by an epidemiologic team, led to the timely recognition of an outbreak of febrile illness among US troops in Haiti. Viral isolation and serological studies were essential in confirming DF. During the surveillance period, DF accounted for at least 30% of the febrile illnesses among hospitalized US troops. Dengue fever is a significant threat to military personnel and civilian travelers in Haiti and has the potential for introduction to and transmission in the United States.

Hepatitis B virus, human immunodeficiency virus type-1, and syphilis among women attending prenatal clinics in Belize, Central America.

Women and their infants may benefit from therapeutic interventions when hepatitis B, human immunodeficiency virus (HIV), or syphilis are detected during the prenatal period. We initiated hepatitis B and HIV screening of women attending prenatal clinics in Belize. Risk factor assessment information for hepatitis B infection and demographic data were determined by interview. Of 543 evaluable women, 81 (14.9%) were seropositive for hepatitis B core antibody (anti-HBc); one woman had asymptomatic hepatitis B surface antigenemia. Antibodies to HIV-1 were detected in one woman. Reactive syphilis serologies were detected in 15 (2.8%) women. Anti-HBc seroprevalence varied by district (range 3.1-43.5%) and by ethnicity (range 0.0-40.9%). Significant identified risks for anti-HBc seropositivity from univariate analyses included being of the Garifuna ethnic group, residence or birth in the Stann Creek or Toledo districts, a reactive syphilis serology, a household size of eight or greater, and five or more lifetime sexual partners. Multivariate analyses identified ethnicity and a reactive rapid plasma reagin as the best predictors of anti-HBc seropositivity. Highly variable differences in anti-HBc prevalence by district may permit the targeting of limited public health resources for education, screening, and prevention programs.

PIP: A cross-sectional study of 543 pregnant women attending prenatal clinics in Belize's 6 districts in a 6-week period in 1993 detected highly variable prevalences of hepatitis B virus (HBV) markers. 81 sera specimens (14.9%) were positive for anti-hepatitis B core antigen (anti-HBc); one woman had asymptomatic hepatitis B surface antigenemia. No HBV markers were detected in the sera of the 1 woman with human immunodeficiency virus (HIV)-1 infection. 15 women (2.8%) had reactive syphilis serologies. Serologic evidence of exposure to HBV was significantly associated with the following sociodemographic factors: single status, age 30-34 years, household size exceeding 8, 5 or more lifetime sexual partners, geographic location (residence in the Stann Creek or Toledo districts), and ethnicity (Garifuna, Creole, and Mayan). In the multivariate analysis, ethnicity and a reactive syphilis result were the only independent predictors of anti-HBc seroprevalence. Anti-HBc seroprevalence varied by district from 3.1-43.5%, with the highest rate in Stann Creek, and by ethnicity from 0 to 40.9%, with the highest rate among the Garifuna. Prevalences were substantially lower among Mestizo-Spanish from the northern and western districts of Orange Walk, Corozal, and Cayo. The overall low prevalence of HBsAg does not support a nationwide prenatal screening program, especially given limited public health care resources. However, this study's findings suggest the feasibility of HBV screening of pregnant women among the Garifuna, Creole, Mayan, and immigrant populations of Belize's Stann Creek and Toledo districts.

Murine immunoglobulin G subclass responses following immunization with live dengue virus or a recombinant dengue envelope protein.

Murine immunoglobulin G (IgG) subclass responses to immunization are restricted to certain subclasses depending on the nature of the immunogen. Immunization with live viruses generally leads to a predominant IgG2a response, which may be the most effective at resisting future challenge due to the unique effector functions of IgG2a. Knowledge of subclass responses following immunization with dengue vaccine candidates may be helpful in determining which candidates are most efficacious. We measured the dengue-specific IgG subclass responses of BALB/c mice following immunization with live dengue-2 virus or with a partially purified recombinant dengue-2 envelope (E) protein. Subclass responses following immunization with live virus were IgG2a > IgG1 > IgG2b > IgG3, as opposed to IgG1 > IgG2a > IgG2b > IgG3 after immunization with recombinant protein. Responses of all subclasses except IgG1 were greater following immunization with live dengue than with the recombinant E protein. Neutralizing antibody titers were also higher after immunization with live virus than with E protein and were positively correlated with dengue-specific IgG2a responses in mice immunized with recombinant E protein. Following separation of the four IgG subclasses by chromatography, the IgG2a fraction exhibited the greatest neutralizing activity. The results seen after immunization with live dengue virus or recombinant E protein in this study are in concordance with studies involving other viruses and viral proteins and may have implications for the development of an effective vaccine for dengue.

Short report: hepatitis E infection in the Brazilian Amazon.

This is the first report of serologic evidence of hepatitis E infection in Brazil. During a community-based survey of healthy individuals, six of 97 gold miners in the Amazon region of Mato Grosso had antibody to the virus. The mining camps have poor sanitation with a great potential for fecal-oral transmission of disease. Since levels of hepatitis E antibodies may quickly wane, studies to directly measure the incidence of seroconversion are planned to determine the intensity of transmission in this area.

Immunization of US soldiers with a two-dose primary series of inactivated hepatitis A vaccine: early immune response, persistence of antibody, and response to a third dose at 1 year.

To study the feasibility of using inactivated hepatitis A vaccine for rapid immunization of US soldiers, 276 randomized seronegative volunteers received one of four regimens: two injections, on day 0 or one each on day 0 and 14, day 0 and 30, or day 0 and 180. A third dose was given on day 380. Among the 256 recipients of two doses, 99% responded with antibody (by ELISA) with few symptoms. A higher percentage of recipients of both doses on day 0 had antibody at day 14 (68% vs. 52% of all others, P < .03). The highest antibody concentrations (711 mIU/mL on day 240) were observed in subjects given a second dose on day 180. Recipients of the third injection developed a median 15-fold rise in antibody within 2 weeks. Virus-neutralizing antibody was detected in high titers after the third dose and neutralized strains of hepatitis A virus from several countries. Vaccines containing 1440 ELISA units of antigen may be useful for rapid immunization.

Administration of hepatitis A vaccine to a military population by needle and jet injector and with hepatitis B vaccine.

Military personnel are an important target population for hepatitis A immunization. Soldiers are often given vaccines by jet injector and may be required to receive multiple vaccines at one time. Formalin-inactivated hepatitis A vaccine containing 360 ELISA units of antigen was evaluated at Fort Campbell. Volunteers received vaccine at 0, 1, and 6 months as follows: group 1, hepatitis A vaccine by needle; group 2, hepatitis A vaccine by jet injector; group 3, hepatitis B vaccine by needle; and group 4, both hepatitis vaccines by needle in separate arms. Immune response and reactogenicity were evaluated. After two doses, recipients of vaccine administered by jet injector had a higher prevalence of antibody than those who received vaccine by needle (93% vs. 79%). By the 8th month, the vaccine was 100% immunogenic by either route or with hepatitis B vaccine. No interaction between hepatitis A and B vaccines was detected.

Early lead challenge and subsequent hypertension in Sprague-Dawley rats.

OBJECTIVE: The consequences of chronic, low grade lead (Pb) burden from earlier exposure on development of hypertension (HT) and cardiovascular disease is, at best, controversial, even though many epidemiological studies suggest the possibility. Accordingly, we examined ability of a short-term Pb challenge to cause later developing HT in rats. METHODS: We gave 12 newly weaned Sprague-Dawley rats (SD) a 1% Pb acetate solution to drink for 6 weeks, while 12 control rats drank water. The rats were further subdivided into groups consuming high and low amounts of sugar. All rats were followed for 4 months after cessation of the Pb challenge. RESULTS: Early Pb challenge caused no significant changes in body weight (BW) from controls; however, systolic blood pressures (SBP) of rats initially receiving Pb continued to rise significantly above their respective dietary controls for months after cessation of challenge. While a high sugar diet alone was associated with elevated SBP, high sugar consumers also challenged with Pb had the highest SBP. Protein excretion did not increase, suggesting, along with other evidence, a lack of significant renal damage. CONCLUSIONS: Previous exposure to Pb can cause subsequent chronic elevations in SBP.

Vaccine-preventable disease susceptibility in a young adult Micronesian population.

Current US military recruit vaccination policy presumes that recruits have had a complete childhood immunization series. This assumption may not be appropriate for recruits from Micronesia, who may have had limited access to modern health care, including immunization programs. During 1988 and 1990, a cross-sectional serosurvey was conducted among 66 US military recruits, 56 from the Federated States of Micronesia and 10 from the Republic of the Marshall Islands, collectively referred to as Micronesia. Antibody seronegativity levels for 12 vaccine-preventable (or potentially so) diseases were: measles (52%), mumps (14%), rubella (21%), varicella (38%), diphtheria (39%) tetanus (0%), polio type 1 (4%), polio type 2 (0%), polio type 3 (14%), hepatitis A (9%), hepatitis B (17%), and hepatitis C (98%). Compared with Army recruits in general, Micronesian recruits were significantly more likely to be seronegative for measles and varicella and seropositive for hepatitis types A and B. Personal histories of disease were felt to be inadequate in predicting antibody status.

Solid-phase antibody capture hemadsorption assay for detection of hepatitis A virus immunoglobulin M antibodies.

A solid-phase antibody capture hemadsorption (SPACH) assay was developed to detect hepatitis A virus (HAV)-specific immunoglobulin M (IgM) antibodies in sera from humans recently infected with hepatitis. The assay is performed with microtiter plates coated with anti-human IgM antibodies to capture IgM antibodies from the test sera. HAV-specific IgM antibody is detected by the addition of HAV hemagglutinating antigen and goose erythrocytes. Hemadsorption of erythrocytes to antigen-antibody complexes attached to the solid phase indicate the presence of IgM antibodies. The SPACH assay was compared to a commercial radioimmunoassay and was found to be equally or more sensitive and specific for the detection of HAV IgM antibodies. The SPACH assay is an alternative, rapid assay that doesn't require hazardous substrates or radioactivity for the detection of HAV-specific antibodies.

Initial report of a hepatitis investigation in rural Belize.

In spring 1991, Belizian health officials expressed concern about a possible hepatitis outbreak in a banana farming district. A study was designed to identify cases and to address the serological prevalence of hepatitis virus markers. Three populations were studied: (i) persons meeting a clinical case definition for hepatitis; (ii) designated banana workers; and (iii) people in a random sample of households in the community. Information was collected using questionnaires and sera were collected for laboratory testing. This report presents the preliminary results of a study conducted in June 1991. Among people who met the clinical case definition, 24% of 42 tested had immunoglobulin M antibody to hepatitis B virus (HBV) core antigen (anti-HBc IgM). In the worker and household survey populations, 284 and 280 people, respectively, were tested for anti-HBc IgM. In each group, 4% were positive. HBV surface antigen was found in 37% of 43 clinical cases, 18% of workers, and 13% of people in the household survey. Among the 3 study populations, the prevalence of HBV core antibody (anti-HBc) ranged from 73% to 81%. Almost all tested persons had evidence of prior hepatitis A virus infection. Evidence of prior infection with hepatitis viruses A and B was widespread, but an aetiology could not be established for most of the clinical cases. However, the prevalence of hepatitis B markers in this population was very high compared to other reports from the Caribbean.

Serum beta-human chorionic gonadotropin, estradiol and progesterone as early predictors of pathologic pregnancy.

We prospectively studied 110 asymptomatic female infertility patients with serial serum measures of beta-human chorionic gonadotropin (hCG), estradiol (E2) and progesterone (P) to determine their sensitivity, specificity, predictive value and test efficiency, alone or in combination, for the prediction of pathologic gestations prior to five weeks after ovulation. Circulating levels of serum beta-hCG, E2 and P were measured at 48- or 72-hour intervals. Seventy-four patients (67%) had viable pregnancies, for which the abnormal changes in steroid levels were defined as: a beta-hCG rise of less than 66% in 48 hours or less than 120% in 72 hours, an E2 decline of greater than 15% in 48 hours or greater than 20% in 72 hours, or a P decline of greater than 25% in 48 hours or greater than 33% in 72 hours. Thirty-six women (33%) had pathologic pregnancies, which included ectopic pregnancies (8), spontaneous or missed abortions (7), blighted ova (anembryonic gestation, 20) and hydatidiform mole (1). For the detection of pathologic pregnancies in this asymptomatic infertility population, the sensitivity of beta-hCG, E2 and P, singly or in combination, ranged from 34% to 78%, and the test efficiency ranged from 68% to 88%. Beta-hCG alone provided the highest sensitivity (78%) and test efficiency (88%). When compared to measuring serial beta-hCG alone, serum E2 or P did not enhance the test efficiency and lowered the sensitivity for the detection of pathologic pregnancies in an asymptomatic infertility population.

Laboratory tests and reference reagents employed in studies of inactivated hepatitis A vaccine.

Procedures to evaluate inactivated hepatitis A vaccines in volunteers have been examined. Solid-phase immunoassays were standardized with reference preparations and have been tested to measure antibody response to immunization and antigen content of vaccines. Following immunization, there was a good correlation between antibody response, determined with commercial immunoassays, and neutralization titres, as measured by the radioimmunofocus inhibition test. However, at lower titres of neutralizing antibody, the commercial immunoassay often yielded negative results. To improve the sensitivity of the immunoassay, the serum volume was increased. A fourfold increase of test serum resulted in greater sensitivity, increasing from 54 to 94%, while retaining 100% specificity. Further increases in the volume of test serum resulted in a loss of specificity. In a comparison of neutralization tests, similar titres of postvaccination sera were obtained by using the HM175/18f cytopathic strain of hepatitis A virus in a plaque reduction assay or the HM175 parental virus in the radioimmunofocus inhibition test. Use of the cytopathic virus obviates the need for radioactively labelled serum and reduces the time taken to conduct neutralization tests. The current laboratory procedures can meet the needs of large field trials of inactivated hepatitis A vaccines.

Hepatitis A in the US Army: epidemiology and vaccine development.

Control of hepatitis A has been an important concern for US military forces in war and peace. Immune serum globulin, although effective, is exceedingly cumbersome to use. The prevalence of antibody against hepatitis A is decreasing in young American soldiers, putting them at risk of hepatitis A during deployment. The US Army has been an active participant in development of hepatitis A vaccine. The first successful cell-culture-derived, formalin-inactivated hepatitis A vaccine was developed at the Walter Reed Army Institute of Research. This prototype vaccine was shown, in 1986, to be safe and immunogenic for humans. Since then we have evaluated the following issues related to the use of inactivated hepatitis A vaccines in military populations. Immunogenicity of vaccine derived from the CLF and HM175 strains; immunogenicity of hepatitis A vaccine given by jet injector; immunogenicity of hepatitis A vaccine when given with hepatitis B vaccine; immunogenicity when given in shortened schedules; safety and immunogenicity in Thai children; and efficacy under field conditions in the tropics. The hepatitis A vaccines which we tested are safe and highly immunogenic. Immunization by jet gun confers immunity equivalent to immunization by needle. Hepatitis A vaccine is equally potent when given with hepatitis B vaccine. Data on rapid immunization schedules and efficacy are under evaluation. We conclude that hepatitis A vaccine is a major improvement in our ability to prevent hepatitis A in soldiers.