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Yellow fever is transmitted through the bite of an infected mosquito. There is an effective vaccine against yellow fever, so if you have been immunised, you can basically rule this disease out. Symptoms of yellow fever range from a mild fever which resolves over a few days to more serious forms with fever, headache, muscle pains, abdominal pain and vomiting. This can progress to bleeding, shock and liver and kidney failure. The liver failure causes jaundice, or yellowing of your skin and the whites of your eyes - hence the name. There's no specific treatment but you should seek medical help urgently if you think you have yellow fever.
This diarrhoeal disease can cause rapid dehydration and death. Cholera is caused by a bacteria, Vibrio cholerae. It's transmitted from person to person by direct contact (often via healthy carriers of the disease) or via contaminated food and water. It can be spread by seafood, including crustaceans and shellfish, which get infected via sewage.
Cholera exists where standards of environmental and personal hygiene are low. Every so often there are massive epidemics, usually due to contaminated water in conditions where there is a breakdown of the normal infrastructure.
The time between becoming infected and symptoms appearing is usually short, between one and five days. The diarrhoea starts suddenly, and pours out of you. It's characteristically described as 'ricewater' diarrhoea because it is watery and flecked with white mucus. Vomiting and muscle cramps are usual, but fever is rare. In its most serious form, it causes a massive outpouring of fluid (up to 20L a day). This is the worst case scenario - only about one in 10 sufferers get this severe form.
It's a self-limiting illness, meaning that if you don't succumb to dehydration, it will end in about a week without any treatment.
You should seek medical help urgently; in the meantime, start re-hydration therapy with oral re-hydration salts. You may need antibiotic treatment with tetracycline, but fluid replacement is the single most important treatment strategy in cholera.
Prevention is by taking basic food and water precautions, avoiding seafood and having scrupulous personal hygiene. The currently available vaccine is not thought worthwhile as it provides only limited protection for a short time.
