title: Variola minor in coalfield areas of England and Wales, 1921-34: Geographical determinants of a national smallpox epidemic that spread out of effective control.
abstract: This paper uses techniques of binary logistic regression to identify the spatial determinants of the last national epidemic of smallpox to spread in England and Wales, the variola minor epidemic of 1921-34. Adjusting for age and county-level variations in vaccination coverage in infancy, the analysis identifies a dose-response gradient with increasing odds of elevated smallpox rates in local government areas with (i) medium (odds ratio [OR] = 5.32, 95% Confidence Interval [95% CI] 1.96-14.41) and high (OR = 11.32, 95% CI 4.20-31.59) coal mining occupation rates and (ii) medium (OR = 16.74, 95% CI 2.24-125.21) and high (OR = 63.43, 95% CI 7.82-497.21) levels of residential density. The results imply that the spatial transmission of variola virus was facilitated by the close spatial packing of individuals, with a heightened transmission risk in coal mining areas of the country. A syndemic interaction between common respiratory conditions arising from exposure to coal dust and smallpox virus transmission is postulated to have contributed to the findings. We suggest that further studies of the geographical intersection of coal mining and acute infections that are transmitted via respiratory secretions are warranted.
authors.affiliation: School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK. Electronic address: matthew.smallman-raynor@nottingham.ac.uk.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Smallman-Raynor
authors.affiliation: School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Rafferty
authors.affiliation: Department of Geography, University of Cambridge, Downing Place, Cambridge, CB2 3EN, UK.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Cliff
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003032:Coal Mining; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D004739:England; D005260:Female; D062305:Geographic Mapping; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011156:Population Density; D012899:Smallpox / Q000453:epidemiology*; D014611:Vaccination / Q000639:trends; D012901:Variola virus / Q000472:pathogenicity; D014852:Wales; D000078329:Workforce
keywords: 1921–34 epidemic; Binary logistic regression; Coal mining; England and Wales; Medical geography; Smallpox