Typhoid fever is caused when the bacterium Salmonella typhi (a.k.a. salmonella, a Gram negative rod bacilus, from the family Enterobacteriaceae) which is spread by the faecal-oral route, leaves the intestine and multiplies throughout the body. Typhoid fever affects 17 million people worldwide every year, with approximately 600,000 deaths annualy. It is more common in less developed countries, especially where the level of hygiene is low, sanitation is poor and the population is not educated in proper food handling.
The usual symptoms in typhoid fever are sustained fever, severe headache, nausea, severe loss of appetite, constipation or sometimes diarrhoea -- and most commonly, a good combination of the above. Mortality rates of 10% have been known to be reduced to less than 1% with appropriate therapy.
If you're stuck in a developing country, to help avoid typhoid, boil drinking water and thoroughly clean and cook all food before consumption. Also, take precautions to dispose of all faeces in a sanitary manner to avoid contamination. A vaccine is also available but does not provide 100% immunity.
Typhoid is treated with antibiotics. Ampicillin, trimethoprim-sulfamethoxazole (Bactrim) and Ciprofloxacin have been known to work. Ciprofloxacin is currently the antibiotic of choice against typhoid.