What should be looked for when assessing a child for measles?

When assessing a child for measles, one key aspect to look for is the presence of mouth ulcers, also known as Koplik spots. These are small, white, shiny lesions that appear inside the cheeks, usually before the onset of the characteristic measles rash. Identifying these spots is crucial because they are a specific indicator that can support the diagnosis of measles, especially in the early stages of the illness.

The other choices, while relevant to general pediatric assessments, do not specifically indicate measles. Signs of dehydration might be important in various contexts, but they are not diagnostic features for measles. A family history of measles and previous vaccinations can provide context to the child's risk and exposure to the virus, yet they do not serve as direct indicators in assessing whether a child currently has measles. Therefore, focusing on signs like mouth ulcers is critical for accurate diagnosis and timely intervention.