Symptoms include fairly sudden onset of fever, severe headache, nausea, abdominal pain, loss of appetite, constipation or diarrhoea. These symptoms can be very severe and there is a one in 10 mortality unless treatment is given. With antibiotics this can be reduced to 1 in 100, although resistance to antibiotic treatment is a growing problem. Multi-drug resistant strains of S typhi have been reported from Asia, the Middle East and Latin America. Typhoid can be carried without causing harm People who get typhoid carry the bacteria in their bloodstream and intestinal tract while they are ill.
People can transmit the disease as long as the bacteria remain in their system.
Most people are infectious just before and during the first week of convalescence. These people are called carriers. Polluted water is the most common source. This explains why typhoid is a worrying problem in disaster areas, where water supply and sewage disposal is disrupted and controls on food lost. But immunisation against typhoid is not a compulsory requirement for entry into any country.