evaluate extreme dispersion parameter for MERS

[avallecam]

This dispersion parameter seems quite extreme? We estimated k = 0.26 (90% CI: 0.11–0.87, 95% CI: 0.09–1.24) - https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2015.20.25.21167 – although this was not analysing the Korea outbreak.

Originally posted by @adamkucharski in #29 (comment)

Regarding the extreme k = 0.02. Should we try to look for studies that estimated and published this from the MERS data? This k value is the one estimated in the superspreading-estimate episode using {fitdistrplus}. Should we add some additional context as papers on MERS with complementary estimates in a callout?