Explaining transmission rate variations and forecasting epidemic spread in multiple regions with a semiparametric mixed effects SIR model.

The transmission rate is a central parameter in mathematical models of infectious disease. Its pivotal role in outbreak dynamics makes estimating the current transmission rate and uncovering its dependence on relevant covariates a core challenge in epidemiological research as well as public health policy evaluation. Here, we develop a method for flexibly inferring a time-varying transmission rate parameter, modeled as a function of covariates and a smooth Gaussian process (GP). The transmission rate model is further embedded in a hierarchy to allow information borrowing across parallel streams of regional incidence data. Crucially, the method makes use of optional vaccination data as a first step toward modeling of endemic infectious diseases. Computational techniques borrowed from the Bayesian spatial analysis literature enable fast and reliable posterior computation. Simulation studies reveal that the method recovers true covariate effects at nominal coverage levels. We analyze data from the COVID-19 pandemic and validate forecast intervals on held-out data. User-friendly software is provided to enable practitioners to easily deploy the method in public health research.

Cigarette smoking and decompression illness severity: a retrospective study in recreational divers.

BACKGROUND: Severe decompression illness (DCI) could be more likely in cigarette smokers because of airway obstruction or vascular disease. The present study evaluated the severity of DCI as a function of cigarette smoking in recreational divers. METHODS: We examined all DCI reports recorded in the Divers Alert Network (DAN) database from 1989 through 1997. Smoking history was quantified as heavy (>15 pack-years), light (0 to 15 pack-years), and never smoked. DCI symptoms were classified as severe (alteration in consciousness, balance or bladder/bowel control, motor weakness, visual symptoms, convulsions), moderate (other neurological symptoms), or mild (pain, skin, or nonspecific symptoms). The proportional odds model and generalized logits were used for the adjusted analysis when accounting for other covariates. RESULTS: There were 4,350 patients included in the analysis. After adjustment for confounding variables, heavy smokers were more likely to have severe vs. mild symptoms than nonsmokers (OR = 1.88) (95% CI 1.36, 2.60) or light smokers (OR = 1.56) (95% CI 1.09, 2.23). Heavy smokers and light smokers were more likely to have severe vs. moderate symptoms than nonsmokers (OR = 1.36) (95% CI 1.06, 1.74) and (1.22) (1.02, 1.46), respectively. Although these data do not reveal whether smoking predisposes to DCI, the results are consistent with a tendency, when DCI occurs, for cigarette smoking to trigger more severe symptoms. CONCLUSIONS: The data suggest that when DCI occurs in recreational divers, smoking is a risk factor for increased severity of symptoms.