- Obesity
- Obsessive compulsive disorder
- Obstetrical tetanus
- Obstructed labour
- Obstructive uropathy
- Oesophageal cancer
- Onchocerciasis
- Orchitis
- Osteomalacia
- Osteomyelitis
- Osteoporosis
- Other bacterial foodborne intoxications e.g. foodborne staphyllococcal intoxication, botulism, clostridium perfringens
- Other bacterial intestinal infections e.g. E.coli, campylobacter
- Other dermatophytoses
- Other mosquito-borne viral fevers e.g. rift valley fever
- Other non toxic goitre
- Other protozoal intestinal diseases e.g. Giardiasis, cryptosporidiosis, isosporiasis etc
- Other superficial mycoses
- Other therapy
- Ovarian cancer
- Ovarian torsion