Characteristics of within-household varicella transmission events associated with school outbreaks in Shanghai, China, 2009-2018.

Transmission of varicella occurs frequently in schools and households. We investigated the characteristics of varicella cases derived from within-household transmission and the modes of varicella transmission between school and household settings in Shanghai, China, from 2009 to 2018. Within-household transmission occurred in 278 households, of which 134 transmission events were between children. Sixty-one household varicella transmission events may be attributed to isolation procedures for infected students during school outbreaks, and 7.6% of school outbreaks were caused by schoolchildren cases derived from within-household transmission. The frequency of 'school-household-school' transmission adds an additional layer of complexity to the control of school varicella outbreaks. Administration of varicella vaccine as post-exposure prophylaxis after exposure is considered to be an effective measure to control varicella spread within households and schools.

[Relationship between risk of childhood acute leukemia and children's and parents' lifestyles and household environment exposure].

OBJECTIVE: To investigate the association between children's and their parents' lifestyles, household environmental exposures and risk of childhood acute leukemia (AL). METHODS: A 1:2 matched case-control study of childhood AL was conducted in Shanghai between April 2011 and January 2014. The study enrolled 66 cases aged < 15, diagnosed with AL and 132 controls matched by age, gender and residence. All of the controls had no hematological diseases or previous history of malignancy. Children who had been adopted and had congenital genetic syndromes such as Down's syndrome or a positive HIV test result were not eligible as either cases or controls. Information was obtained from standardized face-to-face interviews of their parents/guardians with detailed questions on demographic characteristics, lifestyle, and household environment. Conditional logistic regression models were used to analyze effecting factors of childhood AL, odds ratios (OR) and their 95% confidence intervals (CI) were calculated. RESULTS: Among 198 cases, 66 cases were aged (5.0 ± 3.7) years old, and 132 controls were aged (6.0 ± 3.8) years old (t = 0.48, P = 0.523). The paternal drink frequencies of cases and controls were 57.6% (38/66), and 31.1% (41/132), respectively (χ² = 4.91, P = 0.027). And the frequencies of household insecticides usage in the last year in the two groups were 78.8% (52/66), and 65.2% (86/132) (χ² = 3.87, P = 0.049). Chemical exposure during childhood (OR = 4.76, 95% CI: 1.34-16.89), maternal exposure to chemicals (OR = 4.51, 95% CI: 1.65-12.33), household insecticides use during 0-3 years of child (OR = 2.90, 95% CI: 1.31-6.39), and renovating after their children's birth (OR = 3.12, 95% CI: 1.26-7.74) were associated with an increased risk of childhood AL and these differences between the cases and the controls have statistical significance. Besides, we found that frequent contaction with other children during 0-3 years old (OR = 0.32, 95% CI: 0.15-0.69) and ventilation during sleeping in summer (OR = 0.43, 95% CI: 0.18-0.98) were associated with a decreased risk of childhood AL. CONCLUSION: Our results support the association between children's and their parents' lifestyles, household environmental exposures and childhood AL.