Some researchers have argued that the traditional theory of transmission of influenza by person-to-person contact from an infected to a healthy person is an inadequate explanation for the speed with which the disease spreads.
In the 1980s R. Edgar Hope-Simpson undertook detailed studies of burial records in parish registers in six counties in England and Wales – ranging from Devon in the south to Northumberland on the border with Scotland. He found that brief but high excess mortality rates occurred in most places at about the same time and corresponded with eight historic influenza epidemics. Furthermore, the death rates in early epidemics were similar to those found in today’s epidemics.
His research covered the period 1558 to 1837. Hope-Simpson hypothesized that if influenza is transmitted by person-to-person contact then it could not have occurred in such distant places at the same time, particularly in the early years of his study period when the road system was appalling and railways non-existent. He proposed that the influenza virus is latent in individuals who have been infected, and that it is re-activated by some seasonal occurrence, although what exactly this seasonal occurrence was eluded him.[1]
Recently researcher have suggested that “[c]ompelling epidemiological evidence indicates vitamin D deficiency is the ‘seasonal stimulus’” that eluded Hope-Simpson.[2] Vitamin D is synthesized in the skin by exposure to the sun, and vitamin D deficiency is greater in the winter month, hence influenza tends to be a disease of the winter.
The speed with which the Spanish ‘flu travelled would seem to be due to the combination of: a particularly virulent version of the virus; a population debilitated by four years of war, and low levels of Vitamin D. ↩
1. R. E. Hope-Simpson, “Recognition of historic influenza epidemics from parish burial records: a test of prediction from a new hypothesis of influenzal epidemiology,” The Journal of Hygiene (London) October 1983, 91(2), 293–308. passim, <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2129371/?page=1> accessed on 6 March 2014. R. E. Hope-Simpson, “The Method of Transmission of Epidemic Influenza: Further Evidence from Archival Mortality Data”, The Journal of Hygiene, Vol. 96, No. 2 (Apr., 1986), pp. 353-375, p. 353, 362–63. <http://www.jstor.org/stable/3863172> accessed on 8 March 2014.
2. John J Cannell, Michael Zasloff, Cedric F Garland, Robert Scragg, and Edward Giovannucci, “On the epidemiology of influenza”, Virology Journal 2008, 5:29, Conclusion, <http://www.virologyj.com/content/5/1/29#B1> accessed on 3 March 2014. A. Juzeniene, L.W. Ma, M. Kwitniewski, G.A. Polev, Z. Lagunova, A. Dahlback, J. Moan, “The seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin D,” International Journal of Infectious Diseases, 2010 Dec; 14(12), passim <http://www.ncbi.nlm.nih.gov/pubmed/21036090> accessed on 15 March 2014. J. F. Aloia, M. Li-Ng, , “Re: epidemic influenza and vitamin D.” Epidemiology and Infection, 2007 Oct; 135(7): 1095–96, passim <http://www.ncbi.nlm.nih.gov/pubmed/17352842?dopt=Abstract&holding=f1000,f1000m,isrctn> accessed on 15 March 2014.