Household Contacts Of Index Cases Research Articles

Comparative Effectiveness of Baloxavir Marboxil and Oseltamivir Treatment in Reducing Household Transmission of Influenza: A Post Hoc Analysis of the BLOCKSTONE Trial.

The transmission of influenza virus in households, especially by children, is a major route of infection. Prior studies suggest that timely antiviral treatment of ill cases may reduce infection in household contacts. The aim of the study was to compare the effects of oseltamivir (OTV) and baloxavir marboxil (BXM) treatment of index cases on the secondary attack rate (SAR) of influenza within household. A post hoc analysis was done in BLOCKSTONE trial-a placebo-controlled, double-blinded post-exposure prophylaxis of BXM. Data were derived from the laboratory-confirmed index cases' household contacts who received placebo in the trial and also from household members who did not participate in the trial but completed illness questionnaires. To assess the SAR of household members, multivariate analyses adjusted for factors including age, vaccination status, and household size were performed and compared between contacts of index cases treated with BXM or OTV. In total, 185 index cases (116 treated with BXM and 69 treated with OTV) and 410 household contacts (201 from trial, 209 by questionnaire) were included. The Poisson regression modeling showed that the SAR in household contacts of index cases treated with BXM and OTV was 10.8% and 18.5%, respectively; the adjusted relative reduction in SAR was 41.8% (95% confidence interval: 1.0%-65.7%, p = 0.0456) greater with BXM than OTV. Similar reductions were found in contacts from the trial and those included by questionnaire. BXM treatment of index cases appeared to result in a greater reduction in secondary household transmission than OTV treatment.

1978. Vaccine effect on household transmission of omicron and delta SARS-CoV-2 variants in South Korea

Abstract Background We aimed to evaluate household secondary attack rate (SAR) of SARS-CoV-2 variants, omicron and delta, based on index case and contact vaccination status, and antibody level effect of vaccinated index cases on household transmission. Methods A prospective study of 92 index cases and 197 quarantined household contacts was performed. Tests for SARS-CoV-2 variant type and antibody level were conducted in index cases, and results of PCR tests (during the quarantine period) were collected from contacts. Association of antibody levels in vaccinated index cases and SAR was evaluated by multivariate regression analysis. To evaluate the association between antibody levels in vaccinated index cases and household transmission, the probability of transmission was calculated using the logistic regression model. We refit the model for the probability of transmission using the variables that could affect the household transmission (meal with index, contact with index case ≥5/day, respiratory symptoms and immunocompromised status of index patients, and vaccination status of contacts). For this analysis, only vaccinated index cases who tested antibody levels within 7 days of symptom onset or diagnosis, whichever was earlier, were included. Figure 1. Study flow chart A total of 187 SARS-CoV-2 patients were recruited for this study. Of those, 155 patients and 262 of their household members were eligible for inclusion. After excluding unknown primary and reinfection cases, 77 household contacts of 41 index cases with delta variant infection and 120 household contacts of 51 index cases with omicron variant infection were included. Figure 2.The link between index cases and household contacts based on their vaccination status The link between index cases and household contacts according to their vaccination status is shown in Figure. A total of 40, 27, and 10 contacts were linked with 20 unvaccinated index cases, 14 booster-unvaccinated index cases, and 7 booster-vaccinated index cases with delta variant infection, respectively. Among the contacts of index cases with omicron variant infection, 20, 65, and 35 contacts were exposed to 7 unvaccinated, 25 booster-unvaccinated, and 9 booster-vaccinated index cases, respectively. Results SAR was higher in households exposed to omicron variant than those exposed to delta variant. SAR was 35% and 23% for unvaccinated and vaccinated delta variant exposed contacts, respectively. SAR was 44% and 41% for unvaccinated and vaccinated omicron exposed contacts, respectively. Booster dose immunisation of contacts or vaccination of index cases reduced SAR of vaccinated omicron variant exposed contacts. In a model with adjustment, anti-receptor binding domain antibody levels in vaccinated index cases were inversely correlated with household transmission of both delta and omicron variants. Neutralising antibody levels had a similar relationship. When we performed sensitivity analyses using 3 day and 5 day thresholds for the period of antibody test, the results did not differ from the main analyses. Table 1.The secondary attack rate among household contacts of index cases with delta and omicron variant infections according to vaccination status of contactsSAR, secondary attack rate; CI, confidence interval*P-value was calculated using the Fisher’s Exact Test.Table 2.The secondary attack rate according to vaccination status of household contacts linked to that of index casesSAR, secondary attack rate; CI, confidence intervalFigure 3.The association of antibody levels in vaccinated index cases and household transmission. In a model with adjustment for factors that could affect the household transmission, the estimated probabilities of SARS-CoV-2 infection among 132 contacts according to the level of anti-RBD antibodies (A) and neutralising antibodies (B) of 62 index cases. Serum samples for antibody tests were collected within 7 days of symptom onset or diagnosis, whichever was earlier, in vaccinated index cases. Shaded areas indicate 95% confidence intervals. RBD, receptor-binding domain Conclusion Despite of decreased vaccine effectiveness on the transmission of the omicron variant in households, we suggest that enhancing the immunity of all household members through vaccination may help mitigate the current pandemic. Disclosures All Authors: No reported disclosures.

Increased Secondary Attack Rate among Unvaccinated Household Contacts of Coronavirus Disease 2019 Patients with Delta Variant in Japan.

This study aimed to elucidate the household secondary attack rate (HSAR) of the Delta variant in comparison to the Alpha variant, and evaluate the risk factors among unvaccinated household contacts of patients with coronavirus disease 2019 (COVID-19). We studied household contacts of index cases of COVID-19 infected with Delta (L452R mutation), Alpha (N501Y mutation), and wild strain from December 2020 through November 2021 in Itako, Japan. The HSARs of the entire household contact, and the contact of index case with Delta variant were calculated and compared across the risk factors. We used a generalized estimating equation regression model for the multivariate analysis. We enrolled 1257 unvaccinated contacts from 580 households. The HSAR was higher in household contacts of index patients with Delta (48.5%) than with Alpha variant (21.7%) (aOR = 3.34, p = 0.000). In Delta variants, the HSAR was higher in household contacts with spousal relationships to index patients (63.4%) than contacts with other relationships (45.5%) (aOR 1.94, p = 0.026), and was lower in household contacts of index patients aged ≤19 (33.1%) than for contacts of index cases aged 20–59 years (52.6%) (aOR = 0.50, p = 0.027). The result of our study can be used to devise informed strategy to prevent transmission within households.

Risk of Secondary Household Transmission of COVID-19 from Health Care Workers in a Hospital in Spain.

Hospital health care workers are at high risk of developing COVID-19 and transmitting the disease to their family upon returning home; the aim here is to estimate the secondary attack rate of COVID-19 in household contacts of health care workers and their transmission risk factors. COVID-19 cases in the health care workers of an academic hospital in Pamplona, Spain, from 2 March to 26 May 2020, were followed up. The secondary attack rate (SAR) was estimated from cases in household contacts of index cases and their risk factors by Poisson regression. 89 index cases were studied from 99 notified cases in health care workers (89.0%), excluding secondary cases or those who lived alone. Forty-six secondary cases confirmed by the laboratory were found among 326 household contacts, a secondary attack rate of 14.11% (95% CI 10.75-18.31), and 33 household contacts with acute infection symptoms without microbiologic confirmation 10.12% (95% CI 7.30-13.87). Considering all the cases, the secondary attack rate was 27.3 (95% CI 22.75-32.38). Risk factors were the gender and profession of the index case, the number of people living in the household, and the number of persons per bedroom. When the index case health worker used a single room, it had a protective effect, with an incidence rate ratio (IRR) of 0.493 (95% CI 0.246-0.985); Conclusions: The secondary attack rate found among household contacts of health care workers is high. The preventive isolation of health care workers in individual rooms in their house may reduce the transmission in their families.

Secondary Attack Rate among Non-Spousal Household Contacts of Coronavirus Disease 2019 in Tsuchiura, Japan, August 2020–February 2021

Household secondary attack rate (HSAR) by risk factor might have a higher transmission rate between spouses. We investigated risk factors for the HSAR among non-spousal household contacts of patients with coronavirus disease 2019 (COVID-19). We studied household contacts of index cases of COVID-19 in Tsuchiura, Japan, from August 2020 through February 2021. The HSARs of the whole household contacts and non-spousal household contacts were calculated and compared across risk factors. We used a generalized linear mixed regression model for multivariate analysis. We enrolled 496 household contacts of 236 index COVID-19 cases. The HSAR was higher for spousal household contacts (37.8%) than for other contacts (21.2%). The HSAR was lower for non-spousal household contacts with a household size (number of household members) of two (18.2%), compared to the HSAR for contacts with a household size ≥4. The HSAR was higher for non-spousal household contacts of index patients with ≥3 days of diagnostic delay (period between onset and diagnosis) (26.0%) compared to those with ≤2 days’ delay (12.5%) (p = 0.033). Among non-spousal household contacts, the HSAR was low for those with a household size of two and was high for contacts of index patients with a long diagnostic delay.

Incidence of Infection of Enterovirus 71 and Coxsackieviruses A6 and A16 among Household Contacts of Index Cases in Dong Thap Province, Southern Vietnam.

Background Scarce information exists about immunity to hand, foot, and mouth disease (HFMD) among household contacts of index cases in Vietnam and what that means for reducing ongoing HFMD transmission in the community. Methods We analyzed neutralizing antibodies (NT) and the incidence of enterovirus (EVs) infection among household contacts of index cases in a province where HFMD remains endemic. Throat swab and 2 mL blood samples from household contacts were collected at enrollment, during and after 2 weeks follow-up. Results The incidence of EV-A71 infection among household contacts was 40/84 (47.6%, 95% Cl: 36.9-58.3%), compared with 106/336 (31.5%, 95% Cl: 26.6-36.5%) for CV-A6 and 36/107 (33.6%, 95% Cl: 24.7-42.6%) for CV-A16. The incidence of CV-A6 infection was fairly constant across ages; in contrast, CV-A71 and CV-A16 had some variation across ages. At baseline, higher geometric mean titer (GMT) of EV-A71, CV-A6, and CV-A16 antibody titers was found for 25-34-year groups (range 216.3 to 305.0) compared to the other age groups. There was a statistically significant difference in GMT values of CV-A6 and CV-A16 between those who had an infection or did not have infection among households with an index case of these serotypes. Conclusions Our results indicated that adults were becoming infected with HFMD and could be contributing to the transmission. There is, therefore, a need for considering the household setting as an additional target for intervention programs for HFMD.

Prevalence and risk factors for latent tuberculosis infection among household contacts of index cases in two South African provinces: Analysis of baseline data from a cluster-randomised trial.

Household contacts of patients with active pulmonary tuberculosis (TB) often have latent TB infection, and are at risk of progression to disease. We set out to investigate whether index TB case HIV status was linked to a higher probability of latent TB infection among household contacts. Data were collected prospectively from participants in the intervention arm of a household cluster-randomised trial in two South Africa provinces (Mangaung, Free State, and Capricorn, Limpopo). In intervention group households, TB contacts underwent HIV testing and tuberculin skin testing (TST). TST induration was estimated at two cut-offs (≥5mm, ≥10mm). Multilevel Bayesian regression models estimated posterior distributions of the percentage of household contacts with TST induration ≥5mm and ≥10mm by age group, and compared the odds of latent TB infection by key risk factors including HIV status index case age and study province. A total of 2,985 household contacts of 924 index cases were assessed, with most 2,725 (91.3%) undergoing TST. HIV prevalence in household contacts was 14% and 10% in Mangaung and Capricorn respectively. Overall, 16.8% (458/2,725) had TST induration of ≥5mm and 13.1% (359/2,725) ≥10mm. In Mangaung, children aged 0-4 years had a high TST positivity prevalence compared to their peers in Capricorn (22.0% vs. 7.6%, and 20.5% vs. 2.3%, using TST thresholds of ≥5mm and ≥10mm respectively). Compared to contacts from Capricorn, household contacts living in Mangaung were more likely to have TST induration ≥5mm (odds ratio [OR]: 3.08, 95% credibility interval [CI]: 2.13-4.58) and ≥10mm (OR: 4.52, 95% CI: 3.03-6.97). There was a 90% and 92% posterior probability that the odds of TST induration ≥5mm (OR: 0.79, 95% CI: 0.56-1.14) and ≥10mm (OR: 0.77, 95% CI: 0.53-1.10) respectively were lower in household contacts of HIV-positive compared to HIV-negative index cases. High TST induration positivity, especially among young children and people living in Mangaung indicates considerable TB transmission despite high antiretroviral therapy coverage. Household contact of HIV-positive index TB cases were less likely to have evidence of latent TB infection than contacts of HIV-negative index cases.

Active case finding of tuberculosis among household contacts of newly diagnosed tuberculosis patients: A community-based study from southern Haryana.

Background:Active case-finding is provider-initiated and implies systematic searching for TB in individuals who would not spontaneously present to a health service, and bringing them into care for diagnosis and treatment.Aim:The present study was carried out with the objective to assess the yield and feasibility of active case finding strategy among household contacts of newly diagnosed pulmonary TB cases and to determine risk factors in household contact.Methods:This community-based study with cross-sectional design was conducted among the household contacts of all newly diagnosed microbiologically confirmed pulmonary TB patients registered at Tuberculosis Unit (TU), Nuh. Investigator conducted house to house visit and met respective index case and his/her household contacts to build the rapport.Results:In the present study, there were 55 sputum smear-positive index cases and 356 household contacts of index cases. The most common symptom among screening positive household contacts was cough followed by weight loss. A substantial proportion (83.8%) of symptom positive household contacts were investigated for tuberculosis and among them, 18.9% were found to be positive for tuberculosis. The overall prevalence of TB cases among household contacts was found to be 1.97%.Conclusion:The present study concludes that household contact screening for active case finding for TB is a feasible and efficient tool that can potentially result in earlier diagnosis and treatment of active TB, thus minimizing the severity and decreasing transmission. It can also contribute toward improving treatment outcomes, health sequelae, and the social and economic consequences of TB.

Development of a Predictive Model of Tuberculosis Transmission among Household Contacts.

Background Household contacts of patients with tuberculosis (TB) are at great risk of TB infection. The aim of this study was to develop a predictive model of TB transmission among household contacts. Method This was a secondary analysis of data from a prospective cohort study, in which a total of 700 TB patients and 3417 household contacts were enrolled between 2010 and 2013 at two study sites in Peru. The incidence of secondary TB cases among household contacts of index cases was recorded. The LASSO regression method was used to reduce the data dimension and to filter variables. Multivariate logistic regression analysis was applied to develop the predictive model, and internal validation was performed. A nomogram was constructed to display the model, and the AUC was calculated. The calibration curve and decision curve analysis (DCA) were also evaluated. Results The incidence of TB disease among the contacts of index cases was 4.4% (149/3417). Ten variables (gender, age, TB history, diabetes, HIV, index patient's drug resistance, socioeconomic status, spoligotypes, and the index-contact share sleeping room status) filtered through the LASSO regression technique were finally included in the predictive model. The model showed good discriminatory ability, with an AUC value of 0.761 (95% CI, 0.723–0.800) for the derivation and 0.759 (95% CI, 0.717–0.796) for the internal validation. The predictive model showed good calibration, and the DCA demonstrated that the model was clinically useful. Conclusion A predictive model was developed that incorporates characteristics of both the index patients and the contacts, which may be of great value for the individualized prediction of TB transmission among household contacts.

Factors affecting applicability of “home-based interventional model” for active case finding among household contacts of index cases of pulmonary tuberculosis in Kashmir

BackgroundThere are various biological, behavioural and social determinants associated with the epidemiology of pulmonary tuberculosis (P-TB) which have been extensively described in literature. Present study was conducted to know the influence of such factors on the “home-based interventional model” for active case finding among household contacts of index P-TB cases. MethodsIn a quasi-randomized controlled interventional study, the “home-based interventional model” for active case finding was applied to index P-TB cases and their household contacts of interventional group of study subjects. Study was conducted from January 2014 to June 2015 for evaluation of the model in comparison to the existing usual practice of contact tracing. Baseline data regarding factors associated with epidemiology of P-TB likely to influence effectiveness of intervention were collected, collated and analysed. ResultsThe overall acceptance of intervention was 70.74% which was statically significantly influenced by gender (p<0.0001), age group (p=0.0006), education (p<0.0001), occupation (p<0.0001) and relationship of household contacts with index case (p<0.0001). Total 27 (4.51%) cases were detected among contacts. Out of personal and family level characteristics “relationship with index case” (p=0.0418) and “overcrowding in house” (p=0.0017) were found to statistically significantly influencing the effectiveness of interventional model. The prevalent risk factors for TB among contacts, level of exposer of household contacts to index cases, grade sputum positivity and type of index case were not found statistically significantly influencing the yield of interventional model. ConclusionFactors/determinants influencing the applicability of interventional model for active case finding among household contacts were identified and their impact on acceptance and yield of intervention was assessed.

Case-ascertained study of household transmission of seasonal influenza — South Africa, 2013

The household is important in influenza transmission due to intensity of contact. Previous studies reported secondary attack rates (SAR) of 4-10% for laboratory-confirmed influenza in the household. Few have been conducted in middle-income countries. We performed a case-ascertained household transmission study during May-October 2013. Index cases were patients with influenza-like-illness (cough and self-reported or measured fever (≥38°C)) with onset in the last 3 days and no sick household contacts, at clinics in South Africa. Household contacts of index cases with laboratory-confirmed influenza were followed for 12 days. Thirty index cases in 30 households and 107/110 (97%) eligible household contacts were enrolled. Assuming those not enrolled were influenza negative, 21/110 household contacts had laboratory-confirmed influenza (SAR 19%); the mean serial interval was 2.1 days (SD=0.35, range 2-3 days). Most (62/82; 76%) household contacts who completed the risk factor questionnaire never avoided contact and 43/82 (52%) continued to share a bed with the index case after illness onset. SAR for laboratory-confirmed influenza in South Africa was higher than previously reported SARs. Household contacts did not report changing behaviors to prevent transmission. These results can be used to understand and predict influenza transmission in similar middle-income settings.

Effectiveness of clindamycin and intravenous immunoglobulin, and risk of disease in contacts, in invasive group a streptococcal infections.

The use of clindamycin and intravenous immunoglobulin (IVIG) in treatment of invasive group A streptococcal (iGAS) infection, and the need for prophylactic antibiotics in close contacts, remains contentious. Controlled trials are unlikely to be conducted, so prospective, observational studies provide the best data to inform practice. We conducted population-based, prospective, active surveillance of iGAS infections throughout the state of Victoria, Australia (population 4.9 million), from March 2002 through August 2004. Eighty-four cases of severe iGAS infection (streptococcal toxic shock syndrome, necrotizing fasciitis, septic shock, or GAS cellulitis with shock) were identified. Clindamycin-treated patients had more severe disease than clindamycin-untreated patients but lower mortality (15% vs 39%; odds ratio [OR], 0.28; 95% confidence interval [CI], .10-.80). Among those who received concurrent IVIG, the fatality rate was lower still (7%). The adjusted point estimate of the OR for mortality was lower in clindamycin-treated patients (0.31; 95% CI, .09-1.12) and clindamycin plus IVIG-treated patients (0.12; 95% CI, .01-1.29) compared with clindamycin-untreated patients. Three confirmed cases of iGAS infection occurred in household contacts of index cases. The incidence rate of iGAS disease in contacts was 2011 (95% CI, 413-5929) times higher than the population incidence in Victoria. Our data suggest that clindamycin treatment of patients with severe iGAS infections substantially reduces mortality and that this effect may be enhanced by concurrent treatment with IVIG. The dramatically increased risk of iGAS disease among household contacts within 1 month of the index case highlights a potential role for antibiotic prophylaxis.

Epidemiological Aspects of Intrafamilial Spread of HCV Infection in Egyptian Population: A Pilot Study

Aim: Liver disease is a leading cause of morbidity and mortality among Egyptians. The major cause is infection with HCV, with 70 000 up to 140 000 newly reported cases annually. The objectives of this study were to determine the prevalence of anti-HCV antibodies among household contacts of HCV index cases and to identify the possible risk factors of transmission of HCV among Egyptian families. Material and Methods: The present external pilot study (double centre study) was performed on a convenient sample of 125 index cases and their 321 household family contacts recruited from Mansoura & Cairo University where 2 questionnaires were used to collect data from the index & their related contacts. The all were exposed to clinical examinations, routine laboratory testing & screening for the prevalence of Anti-HCV antibodies. Results: The prevalence of anti-HCV seropositivity among household contacts of index cases was found to be 13.7% which husbands of female index cases ranked first followed by wives of male index cases (36.36% versus 17.86% respectively, P

Transmissibility of Influenza

The authors respond: We thank Farrell and colleagues1 for further discussion on our recent article in Epidemiology.2 In a separate transmission study, we estimated similar secondary infection risks among household contacts of index cases with pandemic and seasonal influenza.3 One concern in that study was whether selecting index cases based on a positive rapid test could have led to bias. The study presently under discussion followed a cohort design, which should minimize such selection bias.2 An advantage of both studies is that pandemic and seasonal influenza viruses were cocirculating, allowing fair comparison between the strains under the same study design and procedures. It is challenging to compare secondary infection risks between different studies, given the substantial effects of study design and procedures.4 Our household study was designed before the 2009 pandemic, and we were able to take the opportunity to estimate the household secondary infection risks. For this reason, we agree with Farrell and colleagues1 that a weakness of our study is the small sample size.5 Rather than aiming to detect small differences in transmissibility, we used the existing data for statistical modeling to qualitatively validate our earlier findings.3 As Farrell and colleagues1 have noted, receipt of influenza vaccination could affect the results. Although valid estimation of secondary infection risks is based on the assumption of uniform susceptibility among household contacts,6 we currently lack good correlates of immunity. In a sensitivity analysis, we excluded everyone who received seasonal vaccine (eAppendix Table 3, https://links.lww.com/EDE/A519) and came to similar conclusions. Including or excluding those with antibody titers ≥1:160 did not change secondary infection risks for seasonal and pandemic strains. In summary, the results on relative transmissibility were not influenced by vaccination and thus we believe are generalizable. We chose to use an age cutoff of 15 years based on early work assessing antibody responses in children and adults7 and because this cutoff was used in several studies addressing transmission of influenza within households.8,9 The immune system undergoes changes during puberty, which would support the use of a threshold at this age or even younger.10 Alternatively, expanding the threshold to include all school-age children would have had minimal effect, as only 16 people (4%) in our study were 15–17 years of age. Finally, we completely agree that there is a critical need to elucidate genetic variation between host generations of influenza infection.11 Brendan Klick School of Public Health The University of Hong Kong Pokfulam Hong Kong Special Administrative Region People's Republic of China Hiroshi Nishiura School of Public Health The University of Hong Kong Pokfulam Hong Kong Special Administrative Region People's Republic of China PRESTO Japan Science and Technology Agency Saitama, Japan Benjamin J. Cowling School of Public Health The University of Hong Kong Pokfulam Hong Kong Special Administrative Region People's Republic of China [email protected]

Risk of secondary cases of Clostridium difficile infection among household contacts of index cases

We aimed to estimate the risk of secondary cases of Clostridium difficile infection (CDI) among household contacts of index cases. We reviewed all 2222 patients with confirmed CDI in a region of Quebec, Canada, during 1998-2009. Our laboratory serves a well-defined population for which it is the sole centre providing CDI testing, enabling us to calculate accurate population annual incidence rates of CDI. Cases with the same phone number were verified individually to determine whether they were indeed related. We considered as related two cases occurring in the same household within one year of each other. We estimated that 1061 spouses and 501 children (<25 years-old) lived in the same household as the index cases, of which respectively 5 and 3 developed CDI. Among spouses and children, the attack rate was 4.71/1000 and 5.99/1000 respectively, and the relative risk was 7.61 (95%CI: 5.77-9.78) and 90.6 (95%CI: 33.89-487.64) for the three months after the diagnosis in the index case. Although the relative risk of CDI among household contacts is somewhat increased for a few months, the absolute risk is too low to justify interventions, apart from avoiding unnecessary courses of antimicrobials.

Household screening and multidrug-resistant tuberculosis

Of the estimated half a million people who develop multidrug resistant (MDR) tuberculosis each year, less than 7% are diagnosed and only 1 in 5 of these have access to effective treatment.1 To control this epidemic, dramatically increased efforts are required to scale up case detection and treatment provision. In The Lancet, Mercedes Becerra and colleagues2 report the yield of additional MDR tuberculosis diagnoses that are found by screening household contacts of index cases in Lima, Peru. This study—the largest of its kind to date—found that more than 2% of 4503 household contacts had active tuberculosis at the time the index case was diagnosed.

P305 Pulmonary tuberculosis in household contact of patients with active tuberculosis in Ahvaz, Iran (2003–2005)

Objectives: To determine the prevalence of tuberculosis (TB) among the household contacts. Methodology: It is a retrospective descriptive study conducted in Ahwaz a city in the southwest of Iran, between October and February 2007. Medical files and epidemiological forms of documented TB cases and their contacts in Ahwaz Health Center over the three years period from 2003 to 2005 were reviewed. An index case(IC) was defined as the first TB case identified in the household. A household contact (HC) was defined as an individual who had resided in the household for at least thirty days prior to the diagnosis of tuberculosis in the index case. Secondary cases were defined as TB cases among contacts of the IC. Results: We found 69 patients as IC of TB. Secondary TB in HC and community contacts (CC) was 64 and 15 cases respectively. The studied contact population of 1293 individuals included 352 HC and 941 CC. The prevalence rate of TB for HC and CC was 18.2% and 1.5% respectively (p<0.05). The prevalence rate of TB from IC with smear positive pulmonary tuberculosis (SPPTB) and smear negative pulmonary tuberculosis (SNPTB) for HC and CC was 23.1%, 11.7% and 2.3%, 0.8% respectively (p<0.05). More than 95% of patients with TB in HC were middle aged or elderly. HIV seropositivity and history of IDU addiction was detected in 18.7% of HC with tuberculosis (p<0.05). Conclusions: Tuberculosis is common among household contacts of index cases in Ahvaz (Iran), especially among middle aged and elderly, HIV-infected and IDU addict contacts.

Chemoprophylaxis for household contacts of index cases of invasive non-type b Haemophilus influenzae disease

Macariola, Demetrio R. Jr. M.D.; Ortiz, Joseph M.D.; Brady, Rebecca C. M.D.Editor(s): Peter, Georges M.D. Author Information

Spread of hepatitis C virus infection within families. Investigators of an Italian Multicenter Group.

In 1995, the intrafamilial spread of hepatitis C virus (HCV) was evaluated among 1379 household contacts of 585 HCV antibody-positive HCV RNA-positive subjects (index cases) in Italy. All index cases were patients with histologically proven chronic liver disease. The presence of antibodies to HCV (anti-HCV) was assessed by third-generation enzyme-linked immunosorbent assay (ELISA); the polymerase chain reaction (PCR) was used to test for HCV RNA. The overall anti-HCV prevalence among household contacts of index cases was 7.3% (101/1379); it was 15.6% in spouses and 3.2% in other relatives (P < 0.05; odds ratio (OR), 6.5; 95% confidence interval (CI), 3.5-8.6). Spouses married to index cases for longer than 20 years had a significantly higher anti-HCV prevalence than those married 20 years or less (19.8% vs 8.0%; P< 0.05; OR, 2.8; 95% CI, 1.5-5.3). Parenteral risk factors were more likely to be reported in anti-HCV positive than in anti-HCV negative household contacts. After adjustment for confounders by multiple logistic regression analysis, age greater than 4 5 years (OR, 3.1; 95% CI, 1.6-5.3) and any parenteral exposure (OR, 3.7; 95% CI, 1.7-8.1), were the only independent predictors of the likelihood of anti-HCV positivity among household contacts. Spouses versus other relatives and length of marriage were both no longer associated. These findings suggest that sexual transmission does not seem to play a role in the intrafamilial spread of HCV infection.

Efficacy of Acellular Pertussis Vaccine in Early Childhood After Household Exposure

To evaluate the efficacy of a three-dose primary vaccination with a diphtheria-tetanus tricomponent acellular pertussis vaccine against "typical" pertussis, defined as a spasmodic cough of 21 days or longer with confirmation of Bordetella pertussis infection by culture or serology. Passive monitoring for suspected first household (index) cases of typical pertussis in six areas in Germany comprising 22,505 children vaccinated with study vaccine at 3, 4, and 5 months of age. Blinded, prospective follow-up of household contacts of index cases for incidence and progression of pertussis. Six areas in Germany with a high incidence of pertussis. Four hundred fifty-three households with index cases comprising 360 evaluable contacts eligible for analysis of vaccine efficacy. Vaccine efficacy from attack rates of pertussis in household contacts classified by vaccination status. Of the 173 nonvaccinated household contacts, 96 developed typical pertussis, compared with seven of 112 contacts vaccinated with acellular pertussis vaccine. Vaccine efficacy was consequently calculated to be 88.7% (95% confidence interval, 76.6% to 94.6%). Protection did not wane until at least the time recommended for booster vaccination. None of the analyzed potential confounding factors--age, socioeconomic status, erythromycin treatment, household composition, center effect, and selection bias--influenced study results in favor of the vaccine. Under conditions of intense household exposure, primary vaccination with acellular vaccine protected against pertussis until at least the time recommended for booster vaccination. The vaccine can be expected to be equally or more effective in settings with lower infectious pressure.