Incidence of Scrub Typhus in Rural South India

Area of Science:

• Infectious Diseases
• Epidemiology
• Public Health

Background:

• Scrub typhus is a significant cause of severe undifferentiated fever in endemic Asian regions.
• Population-based incidence and illness data for scrub typhus remain limited.
• Understanding the disease burden is crucial for public health interventions.

Purpose of the Study:

• To determine the population-based incidence of scrub typhus infection and illness.
• To describe the epidemiologic and clinical characteristics of scrub typhus in Tamil Nadu, India.
• To assess the incidence of both symptomatic and asymptomatic Orientia tsutsugamushi infections.

Main Methods:

• A 2-year population-based cohort study was conducted in 37 villages in Tamil Nadu, India.
• Participants were monitored for febrile illness, with blood samples collected for laboratory confirmation.
• A subcohort underwent serial blood sampling to estimate seroconversion rates for Orientia tsutsugamushi.

Main Results:

• The incidence of clinical scrub typhus was 6.0 cases per 1000 person-years.
• Hospitalization occurred in 21.6% of clinical cases, and 8.8% were severe.
• The incidence of asymptomatic seroconversion was 81.2 events per 1000 person-years.

Conclusions:

• This study quantifies the substantial burden of scrub typhus in an endemic Asian region.
• It highlights the incidence of both clinical and asymptomatic Orientia tsutsugamushi infections.
• Findings underscore the need for improved surveillance and control strategies for scrub typhus.