Impact of Human Mobility on COVID-19 Transmission According to Mobility Distance, Location, and Demographic Factors in the Greater Bay Area of China: Population-Based Study.

BACKGROUND: Mobility restriction was one of the primary measures used to restrain the spread of COVID-19 globally. Governments implemented and relaxed various mobility restriction measures in the absence of evidence for almost 3 years, which caused severe adverse outcomes in terms of health, society, and economy. OBJECTIVE: This study aimed to quantify the impact of mobility reduction on COVID-19 transmission according to mobility distance, location, and demographic factors in order to identify hotspots of transmission and guide public health policies. METHODS: Large volumes of anonymized aggregated mobile phone position data between January 1 and February 24, 2020, were collected for 9 megacities in the Greater Bay Area, China. A generalized linear model (GLM) was established to test the association between mobility volume (number of trips) and COVID-19 transmission. Subgroup analysis was also performed for sex, age, travel location, and travel distance. Statistical interaction terms were included in a variety of models that express different relations between involved variables. RESULTS: The GLM analysis demonstrated a significant association between the COVID-19 growth rate ratio (GR) and mobility volume. A stratification analysis revealed a higher effect of mobility volume on the COVID-19 GR among people aged 50-59 years (GR decrease of 13.17% per 10% reduction in mobility volume; P<.001) than among other age groups (GR decreases of 7.80%, 10.43%, 7.48%, 8.01%, and 10.43% for those aged ≤18, 19-29, 30-39, 40-49, and ≥60 years, respectively; P=.02 for the interaction). The impact of mobility reduction on COVID-19 transmission was higher for transit stations and shopping areas (instantaneous reproduction number [Rt] decreases of 0.67 and 0.53 per 10% reduction in mobility volume, respectively) than for workplaces, schools, recreation areas, and other locations (Rt decreases of 0.30, 0.37, 0.44, and 0.32, respectively; P=.02 for the interaction). The association between mobility volume reduction and COVID-19 transmission was lower with decreasing mobility distance as there was a significant interaction between mobility volume and mobility distance with regard to Rt (P<.001 for the interaction). Specifically, the percentage decreases in Rt per 10% reduction in mobility volume were 11.97% when mobility distance increased by 10% (Spring Festival), 6.74% when mobility distance remained unchanged, and 1.52% when mobility distance declined by 10%. CONCLUSIONS: The association between mobility reduction and COVID-19 transmission significantly varied according to mobility distance, location, and age. The substantially higher impact of mobility volume on COVID-19 transmission for longer travel distance, certain age groups, and specific travel locations highlights the potential to optimize the effectiveness of mobility restriction strategies. The results from our study demonstrate the power of having a mobility network using mobile phone data for surveillance that can monitor movement at a detailed level to measure the potential impacts of future pandemics.

Genetically deprived vitamin D exposure predisposes to atrial fibrillation.

AIMS: Low vitamin D level is associated with atrial fibrillation (AF) and may be implicated in its pathogenesis. METHODS AND RESULTS: We studied single nucleotide polymorphisms (SNPs) of vitamin D mechanistic pathways and serum 25-hydroxyvitamin D [25(OH)D] levels in an age- and gender-matched case-control study (controls without AF: mean age 68.6 ± 8.7 years, female 25%; n = 1019; with AF: mean age 69.7 ± 9.5 years, female 30%; n = 156) recruited from a Chinese clinical cohort of patients with stable coronary artery disease. Twelve SNPs involved in the vitamin D mechanistic pathways were studied [biosynthetic: rs4646536, rs10877012, rs3829251, rs1790349; activation: rs2060793, rs1993116; vitamin D-binding protein (VBP)/group-specific component (GC): rs4588, rs7041, rs2282679, rs1155563; and vitamin D receptor: rs1544410, rs10735810]. A genetic risk score (GRS) (0-8) was constructed from SNPs associated with serum 25(OH)D as a proxy to lifelong vitamin D-deficient state. All 4 SNPs involved in the VBP/GC were significantly associated with serum 25(OH)D (rs4588, P < 0.001; rs2282679, P < 0.001; rs7041, P = 0.011; rs1155563, P < 0.001; all other SNPs, P > 0.05). Vitamin D GRS (points 0-8) generated from these 4 SNPs was independently predictive of serum 25(OH)D [B = 0.54, 95% confidence interval (CI) 0.30-0.79; P < 0.001]. Genetically deprived vitamin D status as denoted by a low GRS (0-3) independently predicted an increased risk of AF, compared to a high GRS (4-8) (odds ratio = 1.848, 95% CI 1.217-2.805; P = 0.004). CONCLUSION: Genetically deprived vitamin D exposure predisposes to increased AF among patients with coronary artery disease. Whether VBP/GC may alter the risk of AF via alternative mechanisms warrants further studies.

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.