In most industrialized countries, it is not difficult to find qualified medical assistance if needed. It may be a problem in third world countries, especially in remote areas. Even in major cities medical services can be a questionable and the quality may differ a lot between physicians, public and private hospitals.
If living in a third world country one should identify physicians and hospitals which can be used in case of an emergency. Your travel insurance company will be able to assist you.
When should I seek medical advice?
strong headache especially if there is vomiting and nausea at the same;
rash and fever;
vomiting continuously over several days;
diarrhoea over several days especially if accompanied by fever;