Increased risk of tuberculosis transmission in families with microepidemics

Abstract

In the present study, we analysed: 1) prevalence of TB infection and incidence of disease among family contacts of a cohort of patients with TB; 2) differential characteristics of families with microepidemics and families with ≤1 new case of TB; and 3) efficacy of chemoprophylaxis in this group of contacts.Three thousand and seventy one family contacts of 635 patients with TB were studied. The study consisted of tuberculin skin testing and chest radiography in all cases, and bacteriological studies when active disease was suspected. Contacts were classified as belonging to: families with microepidemics (FME) (those with ≥2 new cases of TB); families with one new case; and families with with no new cases. Chemoprophylaxis was prescribed in contacts following standard recommendations; all were followed up for 12-18 months. Rates of TB infection and disease among families, as well as the incidence of TB disease between those compliant and noncompliant with chemoprophylaxis were compared.Among the 3,071 contacts, 1,264 (41%) were infected and 176 (6%) had TB. Twenty two families with FME (3%) yielded 55 new cases of TB. The prevalence of infection (excluding the TB cases) was 80% in families with FME, 52% in families with one new case, and 41% in families with no new case (odds ratio (OR) 3.7; 95% confidence interval (95% CI) 2.1-6.5). Sputum smears were positive in 53% of cases in FME and 24% in non-FME families (OR 3.4; 95% CI 1.7-6.5). Bronchial sample cultures were positive in 84% of patients from FME families but in only 40% of those from non-FME families (OR 7.5; 95% CI 3.6-15.8).Chemoprophylaxis was prescribed in 356 contacts, of whom 296 complied and generated only one new case of TB, whilst there were 13 new cases among the 60 who did not comply (OR 81.6; 95% CI 26.7-248.7).This study showed the prevalence of infection and incidence of tuberculosis among family contacts of patients with newly diagnosed tuberculosis to be very high. A small number of families with microepidemics accounted for most new cases of tuberculosis, which were also more infectious. The extremely high risk of transmission in these families, together with the proven efficacy of chemoprophylaxis, justifies prescription of chemoprophylaxis to all their members, regardless of age.

Contact investigation for tuberculosis: a systematic review and meta-analysis

“…World Bank Income Gross National Income per capita: low income (≤$1,005 per yr); lower-middle income ($1,006 to $3,975 per yr); upper-middle income ($3,976 to $12,275 per yr); high income (≥$12,276 per yr) [22]. # : [9, 32, 34, 36–39, 41–43, 48, 49, 52, 55, 57–60, 62–67, 69, 71, 73, 74, 77–79, 81, 83–89, 91, 93–95, 97–101, 185–187, 194–196, 199–201 203–215]; ¶ : [10, 28, 30, 31, 102, 103, 105, 107, 109–111, 115, 116, 119, 121–125, 128–138, 142–145, 147–157, 159–184, 188, 189, 193, 202, 216–233]. …”

“…World Bank Income Gross National Income per capita: low income (≤$1,005 per yr); lower-middle income ($1,006 to $3,975 per yr); upper-middle income ($3,976 to $12,275 per yr); high income (≥$12,276 per yr) [22]. # : [9, 33, 34, 38, 42–46, 54, 56–58, 60, 62, 63, 66–68, 70–73, 75, 76, 79, 82, 84, 85, 88, 90, 91, 95, 97, 99–101, 234]; ¶ : [30, 31, 111–113, 116, 119, 120, 122, 134, 135, 137, 138, 148–150, 154, 165, 166, 170, 177]. …”

Multilevel Modeling of Household Contextual Determinants of Tuberculin Skin Test Positivity among Contacts of Infectious Tuberculosis Patients, Umerkot, Pakistan

“…To our knowledge similar data from the study area or other areas of Pakistan are not available for comparison. However, comparable data on the prevalence of M. tuberculosis infection among the contacts of TB patients as high as 41% in Spain, 34 63.9% in Brazil, 35 and 66% in Uganda, 36 have been reported. In a high TB incidence area, 34% of children under the age of 5 years and living in the same household as an index TB case, were reportedly diseased and 14% were infected with M. tuberculosis .…”

Proporsi Infeksi Tuberkulosis dan Gambaran Faktor Risiko pada Balita yang Tinggal dalam Satu Rumah dengan Pasien Tuberkulosis Paru Dewasa

“…Oleh sebab itu, semakin banyak kuman yang dikeluarkan, semakin besar pula risiko seorang anak terkena infeksi. [19][20][21] Risiko infeksi TB lebih tinggi pada subjek dengan kepadatan populasi yang tidak memenuhi syarat (46,8%) dibandingkan dengan memenuhi syarat (36,8%). Beberapa kepustakaan 2,4,6,18 yang menyatakan bahwa tingkat populasi/hunian yang padat akan meningkatkan risiko infeksi TB pada anak.…”