Typhoid and paratyphoid fevers

Overview

Typhoid and paratyphoid fevers, collectively referred to as enteric fever, are caused by systemic infection with Salmonella enterica subspecies serovars Typhi and Paratyphi.

While most non-typhoidal Salmonella spp infections typically produce diarrhoeal illness and less commonly cause bloodstream infection, typhoid and paratyphoid infections produce primarily bacteraemic febrile illnesses, with prolonged high fever, headache, and malaise being characteristic symptoms.

Pathogen(s)

• Salmonella enterica serovar Typhi

• Salmonella enterica serovar Paratyphi (Type A, B and C)

Transmission

Occurs through faecal-oral route via contaminated food or water. Transmission through sexual contact, especially among men who have sex with men, has been documented.

Incubation period:

• Typhoid: Typically 8 to 14 days; Range: 3 to more than 60 days

• Paratyphoid: Typically 1 to 31 days

Infectious period: During acute infection and until stool and urine clearance.

Clinical features

Enteric fever is characterised by an insidious onset of fever, headache, and malaise. Other symptoms include stomach pain, constipation, diarrhoea, cough and loss of appetite. Paratyphoid fever presents with a clinically milder disease compared to typhoid fever.

Risk factors

• Persons who travel to typhoid-endemic areas with poor sanitation and a lack of safe drinking water and clean food

• Persons who had close contact with someone who is infected or had recently been infected with enteric fever

Diagnosis

Blood culture is usually positive for the first two weeks only. Stool and urine culture are positive from the 2nd to 4th weeks. Bone marrow culture is usually positive even after antibiotics have been initiated.

The Widal test is unreliable alone, however, it may provide additional support for the diagnosis when the clinical picture is suggestive.

Treatment and management

Appropriate antibiotics should be started. Patients with enteric fever should be hospitalised.

After successful treatment, patients should be followed up for relapse, chronic carriage, or complications. Chronic carriers (positive stool samples after 6 months) may be treated with a prolonged course of antibiotics.

Precaution, prevention, and control

Vaccination

• Typhoid vaccine may be recommended for travellers going to countries endemic for typhoid fever. Typhoid vaccines are not 100% effective; hence it is important to always practice safe eating and drinking habits to prevent infection.

• There are no vaccines available for paratyphoid fever.

Typhoid carriers should not work as food handlers.

Notification

Who should notify:

• Laboratories

When to notify:

• On laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• As soon as possible. No later than 24 hours from the time of laboratory confirmation.

Resources

Please refer to the Weekly Infectious Diseases Bulletin for the number of confirmed typhoid and paratyphoid cases in Singapore.