Epidemic Investigation

During an outbreak of acute diarrhea in a school hostel in Delhi affecting 47 students over 3 days, the epidemiologist constructs an epidemic curve showing a steep rise followed by a plateau. Attack rates are highest among students who consumed food from the hostel canteen on Day 1. The incubation period ranges from 4 to 36 hours. Stool culture from 3 affected students grows Salmonella typhi. What is the MOST LIKELY source and transmission route for this outbreak?

During an epidemic investigation, the epidemiologist plots the number of cases against time and observes a sharp rise followed by a gradual decline. Which type of epidemic curve pattern is this?

A 28-year-old woman from a rural village in Maharashtra presents to the primary health centre with acute onset fever (39.5°C), severe headache, and neck stiffness for 2 days. On examination, Kernig's sign and Brudzinski's sign are positive. CSF analysis shows pleocytosis with predominant polymorphs, elevated protein (180 mg/dL), and low glucose (18 mg/dL). Gram stain of CSF reveals gram-negative diplococci. Within 48 hours, 5 more cases with identical clinical presentation are reported from the same village. The district epidemiologist is called to investigate. What is the FIRST priority in the epidemic investigation of this outbreak?

During an investigation of a suspected foodborne outbreak of gastroenteritis in a residential colony in Mumbai, the epidemiologist identifies 24 cases over 48 hours. All cases consumed food from a community feast held 2 days ago. The incubation period for suspected organisms ranges from 1–6 hours (Staphylococcus aureus) to 12–36 hours (Salmonella). A histogram of case onset times shows a sharp peak at 6–8 hours after the feast, with a tail extending to 24 hours. What is the most likely causative organism, and what does the epidemic curve pattern suggest?

In epidemic investigation, which of the following is the PRIMARY objective of establishing a case definition?