Ebola hemorrhagic fever, Kikwit, Democratic Republic of the Congo, 1995: risk factors for patients without a reported exposure.

In 1995, 316 people became ill with Ebola hemorrhagic fever (EHF) in Kikwit, Democratic Republic of the Congo. The exposure source was not reported for 55 patients (17%) at the start of this investigation, and it remained unknown for 12 patients after extensive epidemiologic evaluation. Both admission to a hospital and visiting a person with fever and bleeding were risk factors associated with infection. Nineteen patients appeared to have been exposed while visiting someone with suspected EHF, although they did not provide care. Fourteen of the 19 reported touching the patient with suspected EHF; 5 reported that they had no physical contact. Although close contact while caring for an infected person was probably the major route of transmission in this and previous EHF outbreaks, the virus may have been transmitted by touch, droplet, airborne particle, or fomite; thus, expansion of the use of barrier techniques to include casual contacts might prevent or mitigate future epidemics.

Measles outbreak in Juneau, Alaska, 1996: implications for future outbreak control strategies.

OBJECTIVE: To determine the most effective outbreak control strategy for school-based measles outbreaks as the proportion of children with two doses of measles-containing vaccine (MCV) increases. SETTING: A school-based measles outbreak during 1996 involving 63 cases in Juneau, Alaska (population 29 288), where systematic revaccination with MCV was not implemented. DESIGN: A retrospective evaluation using chain-of-transmission data of three possible outbreak control strategies: no school revaccination, targeted school revaccination (affected schools only), and community-wide school revaccination (all schools). Two-dose MCV coverage among students was estimated from school vaccination records and a survey issued to parents. PRIMARY OUTCOME MEASURES: Potentially preventable cases of measles and doses of MCV administered per case prevented. RESULTS: Two-dose MCV coverage among Juneau students was estimated to be 44% and 53% immediately before and after the outbreak, respectively. Of all the measles cases, an estimated 24 to 28 and 27 to 31 were potentially preventable by the targeted and community-wide school revaccination strategies, respectively. Either strategy might have optimally decreased the outbreak duration by 1 month, sparing one of seven affected schools and 10 of 12 unvaccinated children who had measles. Approximately 133 to 155 and 139 to 160 doses of MCV per case prevented would have been required for targeted and community-wide school revaccination, respectively. CONCLUSIONS: Either targeted or community-wide school revaccination would have been effective control strategies for this outbreak. Targeted school revaccination is probably the intervention of choice for school-based measles outbreaks in larger communities with higher two-dose MCV coverage. As two-dose MCV coverage continues to increase in the United States, public health control measures to respond to outbreaks need to be reevaluated.

Estimating the maximum effective dose in a quantitative dose-response experiment.

A simulation study was conducted to compare several procedures for estimating the maximum effective dose in a quantitative dose-response experiment. Using four equally spaced dose levels, data were generated from four different model types: the quadratic growth curve, the Mitcherlich growth curve, the linear-linear plateau spline model, and the quadratic-linear plateau spline model. Each model type was parameterized to create three different model ranges, and for each range, data were generated from populations with three different standard deviations. The existence of unique dose-response curves is assumed; thus, all the procedures compared in this paper require that the data have been modeled by a polynomial or nonlinear regression model. An attempt was made to fit each generated data set with each of the four model types. Maximum effective dose estimation procedures were applied to a data set only when the data were adequately described by a given model. The stimulation indicated that the estimate of the maximum effective dose is influenced more by the choice of model than by the method of estimation. Because of the consistently low estimates produced when the data were modeled by the linear-linear plateau spline, this model is not recommended for use an maximum effective dose estimation experiments. The simulation also demonstrated that the design failed to provide sufficient information about the form of the dose-response curve. Designs with more than four dose levels should be considered.

The role of young children in a community-wide outbreak of hepatitis A.

An Hasidic Jewish community has experienced recurrent hepatitis A outbreaks since 1980. To assess risk factors for illness during a 1985-6 outbreak, the authors reviewed case records and randomly selected 93 households for an interview and serologic survey. In the outbreak, 117 cases of hepatitis A were identified, with the highest attack rate (4.2%) among 3-5 year olds. Among the survey households, the presence of 3-5 year olds was the only risk factor that increased a household's risk of hepatitis A (indeterminant relative risk, P = 0.02). Furthermore, case households from the outbreak were more likely to have 3-5 years olds than were control households from the survey (odds ratio = 16.4, P < 0.001). Children 3-5 years old were more likely to have hepatitis A and may have been the most frequent transmitters of hepatitis A in this community. Hepatitis A vaccination of 3-5 year olds can protect this age group and might prevent future outbreaks in the community.

Correlates of gun-carrying among adolescents in south Louisiana.

In the majority of episodes of fatal interpersonal violence, the weapon used is a firearm. Amid frequent reports of youths carrying weapons, including firearms, we conducted a case-control study to identify risk factors for being charged with gun-carrying and gun-carrying, per se, among adolescents in Jefferson Parish, Louisiana. Cases were defined as incidents of gun-carrying among adolescents < 19 years of age, legally charged in the Jefferson Parish, Louisiana, juvenile court from January 1, 1992, through April 15, 1993. For each case, we randomly drew three age-, gender-, and school-matched control subjects from the enrollment rosters of the Jefferson Parish public schools and administered a questionnaire. The data set comprised 38 case subjects and 103 matched control subjects. Thirty (29%) control subjects reported gun-carrying. Both case subjects and gun-carrying control subjects reported self-defense (40%) as the main reason for gun-carrying. Most case subjects (25 [66%]) were African Americans, but only 8 (27%) gun-carrying and 27 (37%) non-gun-carrying control subjects were African Americans. Case subjects were significantly more likely than gun-carrying control subjects to report being African American (odds ratio [OR] = 5.3, 95% confidence intervals [CI] = 1.6, 17.5). In crude analyses, case subjects were more likely than non-gun-carrying control subjects to report adult-male unemployment among households with adult men, to foresee a likelihood to be shot in school, to have seen a shooting, to use marijuana, to watch television > 6 hours per day, and to be African American. After the effect estimates were adjusted in conditional logistic regression modeling, case subjects were more likely than non-gun-carrying control subjects to report adult-male unemployment among households with adult men, using marijuana, and watching television > 6 hours per day (OR = 8.6, 95% CI = 1.2, 61,2; OR = 11.7, 95% CI = 2, 70.2; and OR = 6.5, 95% CI = 0.8, 51.9, respectively). Gun-carrying control subjects were significantly more likely than non-gun-carrying control subjects to report their school not safe, having seen a shooting, using marijuana, and having fired a gun (OR = 9, 95% CI = 1, 82.1; OR = 7, 95% CI = 1.3, 38.2; OR = 6.8, 95% CI = 1.8, 25.5; and OR = 17, 95% CI = 1.8, 156.6, respectively). We found that gun-carrying was very common, and that adolescent youths who carry guns were more likely to have familiarity with guns and experience with or perception of an unsafe environment. Together, these lead to the conclusion that gun-carrying is a common response of youths who live in a risky environment, who do not have the social support to learn how to deal effectively with that risk, and who have access to guns, which they think may provide them with some protection.

Cardiac effects of standard-dose halofantrine therapy.

The antimalarial drug halofantrine hydrochloride has been associated with cardiac arrhythmias. This is a report of a study on the cardiac effects of standard-dose halofantrine (24 mg/kg) on a sample of 48 patients selected from a group of 402 Dega (Montagnard) refugees treated for Plasmodium falciparum infection. Prolongation of the rate-corrected QT interval (QTc) on the electrocardiogram (ECG) was used as an indicator of risk for halofantrine-associated cardiac arrhythmias. We found that standard-dose halofantrine was associated with a lengthening of the mean QTc from 0.04 sec(1/2) to 0.44 sec(1/2). Two patients had a QTc increase of greater than 25%, but none had a follow-up QTc of more than 0.55 sec(1/2), an interval length generally considered to be a risk factor for ventricular arrhythmias. Regression analysis indicated that pretreatment ECGs were poorly predictive of QTc lengthening during therapy, although pretreatment ECGs may be useful to evaluate patients with pre-existing cardiac conditions. The manufacturer has recommended that the halofantrine dose not exceed 24 mg/kg and revised the list of medication contraindications to include some cardiac conditions. Clinicians should weigh a patient's risk, including history of cardiac disease and availability of alternative therapy before use of halofantrine.