Darwin worked very hard and neglected his health.

From the clinical syndromes described, modern physicians concluded that Darwin suffered from three painful diseases:

• cyclical vomiting syndrome,
• chagas disease (an acute infectious disease caused by the parasite Trypanosoma cruzi),
• gastric ulcers caused by Helicobacter pylori infection.

Darwin's records included a reference to a painful insect bite during his stay in Argentina, after which he suffered a prolonged fever associated with chills (the insect was probably infected with Trypanosoma cruzi).