UCLA

Yellow fever is a vaccine-preventable acute viral hemorrhagic disease. Children are vaccinated in the Democratic Republic of Congo (DRC), beginning at nine months. Yellow fever transmission can also be prevented through mosquito control and bite prevention. Nonetheless, there was an outbreak of yellow fever in DRC in 2016. The potential for yellow fever outbreaks persists due to an abundance of mosquitos and immunity gaps. Costly and logistically challenging vaccination campaigns are often needed once an outbreak is detected.

This research aims to use diverse methodologies to examine the background situation and risk factors of the 2016 DRC yellow fever outbreak and identify opportunities to effectively mitigate or prevent future outbreaks. Chapter 1 provides background about the virus, transmission, epidemiology, prevention, and health infrastructure in DRC. Chapter 2 explores the level of childhood yellow fever vaccination in DRC, identifies demographic and behavioral factors associated with vaccination, and geographic differences in yellow fever vaccination in DRC using the Demographic and Health Survey (DHS). Vaccination coverage varied by the source of information (69.9% to 82.9%). Maternal factors, like antenatal and postnatal care and delivery at a government or public facility, were influential for childhood vaccination. Understanding these factors, specifically for yellow fever in DRC, can help guide immunization efforts. Chapter 3 identifies spatial patterns in reported yellow fever cases and analyzes the spatial relationship between sociodemographic, environmental, and organizational risk factors and yellow fever using statistical and spatial analyses. Reported yellow fever cases were clustered among certain health zones in DRC, and several factors may be associated with reported cases. Chapter 4 approximates the outbreak using a mathematical model to evaluate interventions. Many resources are needed for outbreak response, so it may be most useful to strengthen the health delivery system and integrate widespread interventions before an outbreak, which establishes capacity to detect and respond to all outbreaks.

These studies bring much-needed attention to the outbreak of yellow fever in DRC and highlight potential deficiencies in immunity, factors that may contribute to increased transmission and where cases are reported, and how outbreaks can be prevented by investing in a comprehensive disease prevention infrastructure.