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SUMMARY:Trade-off theory and the surprising efficacy of early public healt
 h interventions: the case of faecal-oral diseases in England c.1840-1930 -
  Romola Davenport (Cambridge Group for the History of Population and Socia
 l Structure)
DTSTART:20230621T110000Z
DTEND:20230621T120000Z
UID:TALK202609@talks.cam.ac.uk
CONTACT:Dr Ciara Dangerfield
DESCRIPTION:The ‘trade-off’ theory of pathogen evolution predicts that
  pathogen life histories represent a (complex) compromise between virulenc
 e and transmission (Acevedo et al.\, 2019\; Anderson & May\, 1982\; Ewald\
 , 1983). The evolutionary trade-offs involved vary depending on transmissi
 on mode(s) among other factors\, and result in a very wide range of virule
 nce from benign to extremely lethal. Here I consider the history of infect
 ious disease mortality in England from the perspective of trade-off theory
 \, with particular reference to faecal-oral diseases in the 19th century.\
 nFaecal-oral diseases are caused by ingestion of infected faeces via conta
 minated water\, food or via flies or touch. The importance of these transm
 ission pathways varies for different faecal-oral pathogens\, and virulence
  is associated with water-borne transmission (Ewald\, 1991). In 19th centu
 ry England the most lethal faecal-oral diseases were ‘Asiatic’ cholera
 \, typhoid and dysentery\, with case-fatality rates of perhaps 20 %. Diarr
 hoeal diseases on the other hand killed mainly very young children and the
  elderly and are assumed to have had very low case-fatality rates. As wate
 r supplies gradually improved after c. 1850\, the most lethal diseases und
 erwent major declines. Infant diarrhoeal mortality on the other hand did n
 ot decline substantially until the 1910s. I suggest that the precocious de
 clines of the most lethal faecal-oral diseases reflected the relative ease
  with which waterborne transmission of these diseases was disrupted by ear
 ly and relatively crude attempts to source clean water. Infant diarrhoeal 
 mortality on the other hand failed to fall even after decades of very cost
 ly improvements in water treatment and sewerage\, and the eventual disappe
 arance of summer diarrhoeal epidemics remains poorly understood. This para
 dox mirrors current conundrums in WaSH (Water\, Sanitation and Hygiene) pr
 ogrammes globally: while huge gains have been made in controlling typhoid 
 and cholera\, infant diarrhoeal disease has proven more intractable. This 
 suggests that public health interventions may often face a problem of dimi
 nishing returns\, because early interventions often fortuitously target 
 ‘low-hanging fruit’\, that is\, diseases that are both relatively leth
 al\, and relatively easy to control.
LOCATION:Zoom
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