re: Diseases and causes of death - one week in London - 1665

Griping of the guts sounds like the runs/ diarrhea where serious enough one could die of dehydration. Remember you would not want to drink the water of 17th century London.
Dysentery and cholera were major killers. This was before microscopes and the discovery of bacteria and viruses.
Best to live way out in the country during that time.