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We report temporal patterns of viral shedding in 94 laboratory-confirmed COVID-19 patients and modelled COVID-19 infectiousness profile from a separate sample of 77 infector-infectee transmission pairs. We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% of transmission could occur before first symptoms of the index. Disease control measures should be adjusted to account for probable substantial pre-symptomatic transmission.

To identify risk variants for lung cancer, we conducted a multistage genome-wide association study. In the discovery phase, we analyzed 315,450 tagging SNPs in 1,154 current and former (ever) smoking cases of European ancestry and 1,137 frequency-matched, ever-smoking controls from Houston, Texas. For replication, we evaluated the ten SNPs most significantly associated with lung cancer in an additional 711 cases and 632 controls from Texas and 2,013 cases and 3,062 controls from the UK. Two SNPs, rs1051730 and rs8034191, mapping to a region of strong linkage disequilibrium within 15q25.1 containing PSMA4 and the nicotinic acetylcholine receptor subunit genes CHRNA3 and CHRNA5, were significantly associated with risk in both replication sets. Combined analysis yielded odds ratios of 1.32 (P < 1 × 10 −17 ) for both SNPs. Haplotype analysis was consistent with there being a single risk variant in this region. We conclude that variation in a region of 15q25.1 containing nicotinic acetylcholine receptors genes contributes to lung cancer risk.Lung cancer is frequently cited as a malignancy attributable solely to environmental exposures -primarily cigarette smoke. However, evidence that genetic factors influence lung cancer © 2008 Nature Publishing Group Correspondence should be addressed to C.I.A. (E-mail: camos@mdanderson.org). 6 These authors contributed equally to this work. AUTHOR CONTRIBUTIONS Texas: C.I.A. and M.R.S. conceived of this study. M.R.S. established the Texas lung cancer study. C.I.A. supervised and performed the analyses. G.M. provided oversight in manuscript development and in the conduct of genetic studies. I.P.G., Q.D., Q.Z., W.V.C. and X.G. performed statistical analyses. S.S. developed and implemented statistical procedures for joint analysis. X.W. and J. Direct evidence for a genetic predisposition to lung cancer is provided by the increased risk associated with constitutional TP53 (tumor protein p53) 4 and RB1 (retinoblastoma) 5,6 gene mutations, rare mendelian cancer syndromes such as Bloom's 7 and Werner's syndromes 8 , and strongly familial lung cancer 9 . The genetic basis of inherited susceptibility to lung cancer outside the context of these disorders is at present undefined, but a model in which high-risk alleles account for all of the excess familial risk seems unlikely. Alternatively, part of the inherited genetic risk may be caused by low-penetrance alleles. This hypothesis implies that testing for allelic association should be a powerful strategy for identifying alleles that predispose to lung cancer.We conducted a genome-wide association study (GWAS) of histologically confirmed nonsmall cell lung cancer (NSCLC) to identify common low-penetrance alleles influencing lung cancer risk. To minimize confounding effects from cigarette smoking and increase the power to detect genetic effects, we frequency matched controls to cases according to smoking behavior. We also matched controls to cases by age (within 5 year categories) and sex, and we further matched former smokers by year...