The serial intervals of seasonal and pandemic influenza viruses in households in Bangkok, Thailand.

The serial interval (SI) of human influenza virus infections is often described by a single distribution. Understanding sources of variation in the SI could provide valuable information for understanding influenza transmission dynamics. Using data from a randomized household study of nonpharmaceutical interventions to prevent influenza transmission in Bangkok, Thailand, over 34 months between 2008 and 2011, we estimated the influence of influenza virus type/subtype and other characteristics of 251 pediatric index cases and their 315 infected household contacts on estimates of household SI. The mean SI for all households was 3.3 days. Relative to influenza A(H1N1)pdm09 (3.1 days), the SI for influenza B (3.7 days) was 22% longer (95% confidence interval: 4, 43), or about half a day. The SIs for influenza viruses A(H1N1) and A(H3N2) were similar to that for A(H1N1)pdm09. SIs were shortest for older index cases (age 11-14 years) and for younger infected household contacts (age ≤15 years). Greater time spent in proximity to the index child was associated with shorter SIs. Differences in the SI might reflect differences in incubation period, viral shedding, contact, or susceptibility. These findings could improve parameterization of mathematical models to better predict the impact of epidemic or pandemic influenza mitigation strategies.

Effect of intensive hand washing education on hand washing behaviors in thai households with an influenza-positive child in urban Thailand.

This study assessed the effect of intensive education on self-reported frequency of hand washing (FHW), measured quality of hand washing (QHW), and measured scores of knowledge, attitude, and practice (KAP) after 7 days and 90 days home-based intensive education of participants (aged >7 years) in households with a influenza-positive child. The authors provided intensive hand washing education using interactive participation including individual training, self-monitoring diary, provision of soap, and so on. There were significant improvements on FHW and QHW on day 7, control group (n(1) = 135) reported 3.9 hand washing episodes/day, whereas the intervention group (n(2) = 140) reported 5.7 episodes/day; control group (n(1) = 164) obtained a 3.2 measured quality score, whereas the intervention group (n(2) = 166) obtained a score of 6.4. Pre-education and 90 days post-education, FHW significantly improved by 2 episodes/day and QHW increased by 3 scores/episode. Knowledge of influenza and hand washing following coughing/sneezing showed significant improvement, but attitude modification toward severity of influenza requires a more intensified and longer intervention.

Findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in Bangkok, Thailand.

BACKGROUND: Evidence is needed on the effectiveness of non-pharmaceutical interventions (NPIs) to reduce influenza transmission. METHODOLOGY: We studied NPIs in households with a febrile, influenza-positive child. Households were randomized to control, hand washing (HW), or hand washing plus paper surgical face masks (HW + FM) arms. Study nurses conducted home visits within 24 hours of enrollment and on days 3, 7, and 21. Respiratory swabs and serum were collected from all household members and tested for influenza by RT-PCR or serology. PRINCIPAL FINDINGS: Between April 2008 and August 2009, 991 (16·5%) of 5995 pediatric influenza-like illness patients tested influenza positive. Four hundred and forty-two index children with 1147 household members were enrolled, and 221 (50·0%) were aged <6 years. Three hundred and ninety-seven (89·8%) households reported that the index patient slept in the parents' bedroom. The secondary attack rate was 21·5%, and 56/345 (16·3%; 95% CI 12·4-20·2%) secondary cases were asymptomatic. Hand-washing subjects reported 4·7 washing episodes/day, compared to 4·9 times/day in the HW + FM arm and 3·9 times/day in controls (P = 0·001). The odds ratios (ORs) for secondary influenza infection were not significantly different in the HW arm (OR = 1·20; 95% CI 0·76-1·88; P-0.442), or the HW + FM arm (OR = 1·16; 95% CI .0·74-1·82; P = 0.525). CONCLUSIONS: Influenza transmission was not reduced by interventions to promote hand washing and face mask use. This may be attributable to transmission that occurred before the intervention, poor facemask compliance, little difference in hand-washing frequency between study groups, and shared sleeping arrangements. A prospective study design and a careful analysis of sociocultural factors could improve future NPI studies.