In the context of an outbreak investigation in microbiology, which individual is most likely to be identified as the source of infection for a child who develops symptoms after attending a daycare?

• A. Another child at the daycare who was recently ill
• B. A pet that does not leave the house
• C. A family member who lives in a different city
• D. A teacher who has no symptoms

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of the 'source of infection' in an outbreak investigation. The source is the individual or object from which the infection was transmitted to the case in question.
2. Step 2: Consider the incubation period and timing of symptom development. The source is typically someone who was infectious before or during the time the child was exposed.
3. Step 3: Evaluate the likelihood of transmission based on proximity and interaction. Individuals who have close and frequent contact with the child, such as other children at the daycare, are more probable sources.
4. Step 4: Exclude less likely sources based on their exposure and symptom status. For example, a pet that does not leave the house or a family member living in a different city is less likely to be the source due to limited contact or geographic separation.
5. Step 5: Conclude that the most likely source is another child at the daycare who was recently ill, as this individual had both the opportunity and timing to transmit the infection.