Typhoid fever in children aged less than 5 years

Area of Science:

• Epidemiology
• Infectious Diseases
• Public Health

Background:

• Typhoid fever incidence calculation is crucial for optimizing immunisation schedules and vaccine selection in developing nations.
• Existing hospital-based data suggesting low risk in children under 5 requires community-based validation.
• A prospective study in Delhi, India, was conducted to re-evaluate typhoid fever risk in preschool-aged children.

Purpose of the Study:

• To determine the incidence of typhoid fever in preschool-aged children.
• To challenge the prevailing notion that typhoid fever primarily affects school-aged children and adults.
• To inform public health strategies regarding typhoid immunisation.

Main Methods:

• A longitudinal community-based study involving active surveillance was conducted in Kalkaji, Delhi.
• 8172 residents from 1820 households were visited twice weekly for case detection over a one-year period (Nov 1995 - Oct 1996).
• Blood samples were collected from febrile patients, and Salmonella typhi-positive cases were treated with ciprofloxacin.

Main Results:

• A total of 63 culture-positive typhoid fever cases were identified.
• Notably, 44% (28 cases) occurred in children under 5 years of age.
• The incidence rate per 1000 person-years was highest in children under 5 (27.3), followed by those aged 5-19 years (11.7), and adults aged 19-40 years (1.1).
• Significant differences in incidence were observed across all age groups (p<0.001).
• Morbidity, including fever duration, symptoms, and hospitalisation rates, was similar between children under 5 and older individuals.

Conclusions:

• The study findings contradict the common belief that typhoid fever predominantly affects school-aged children and adults.
• Typhoid fever represents a significant and common cause of morbidity in children between 1 and 5 years of age.
• Reassessment of the optimal age for typhoid immunisation and vaccine selection is warranted based on these findings.