Certification Board of Infection Control and Epidemiology (CBIC) Practice Exam 2025 – The All-in-One Guide for Exam Success

The first step in vector transmission before infecting a host involves the vector invasion by the microbe. In the context of vector-borne diseases, vectors, such as mosquitoes or ticks, carry pathogens and play a crucial role in the transmission process. For infection to occur, the pathogen must first invade the vector, where it can replicate or undergo necessary developmental stages. This invasion allows the pathogen to subsequently be transmitted to a host when the vector feeds on their blood or tissue.

Ingestion of the pathogen is not applicable here, as the vector typically acquires the pathogen from an infected host rather than ingesting it in a conventional sense like food consumption. Host immune response activation occurs after the pathogen has entered a new host and is not a precursor to vector transmission. Development of the pathogen can occur within the vector after invasion but is not the initial step in the transmission process itself. Therefore, the sequence logically begins with vector invasion by the microbe before any subsequent steps can take place in the infection process.