A fever illness appeared in three neighboring towns of one province, rising from 12 to 400 cases in five weeks. No cases were reported outside that province. How should this outbreak be classified?

A newly identified respiratory virus was reported in 90 countries on six continents within three months, with more than 200,000 confirmed cases. Which classification do these data support?

Health records from one district show about 50 malaria cases every month for the past eight years, with no month above 60. What do these data show about malaria there?

Measles cases in one city climbed from 8 to 260 over seven weeks. Health teams found no cases in the surrounding provinces during those weeks. What does this pattern show?

Disease X caused 600 cases in three neighboring towns. Disease Y caused 12,000 cases in 45 countries across four continents. How should the two be classified?

In week 1, a new flu strain was found only in one country. By week 12, 40 countries on five continents reported cases. What changed between week 1 and week 12?

Weekly new cases of a school illness were 5, 22, 75, 210, 190, 90 and 35. Sick students were kept home starting at the end of week 4. Which conclusion do these data support?

New cases reported each week during an outbreak were 8, 30, 95, 240, 260, 120 and 40. When did the outbreak peak?

A town began a handwashing campaign at the start of week 3. Weekly new cases of a stomach illness were 10, 45, 160, 150, 60 and 20. Which claim about the campaign do these data support?

During the first six weeks of an outbreak with no control measures, new cases were 4, 9, 20, 44, 96 and 205. What does this pattern show about the spread?

In weeks 6, 7 and 8 of an outbreak, the new cases reported each week were 100, 80 and 50. What happened to the total number of people infected over those three weeks?

Two villages were tracked through the same cholera outbreak. One had a chlorinated well and latrines; the other did not. Rates were 6 cases per 1,000 people and 55 per 1,000. Which statement do these data support?

During a measles outbreak, 4,000 vaccinated students recorded 12 cases and 4,000 unvaccinated students recorded 160 cases. What do these data show about the vaccine?

Factory A sent infected workers home for 10 days, but Factory B had no such rule. Over the same eight weeks, Factory A recorded 25 cases per 1,000 workers and Factory B recorded 130 per 1,000. What do the rates show?

Town A reported 300 cases among 60,000 residents. Town B reported 90 cases among 6,000 residents. In which town was a resident more likely to catch the disease?

Clinic A installed handwashing stations; Clinic B did not. Clinic A recorded 18 infections per 1,000 patients and Clinic B recorded 70 per 1,000. Which reasoning links this evidence to the claim that handwashing helped?

In a study of bacterial pneumonia, 150 patients received an antibiotic plus usual care and 6 died; 150 received usual care alone and 30 died. Which statement do these data support?

During a flu outbreak, 200 patients given antibiotics and 200 given rest and fluids were compared. Within a week, 88 and 90 patients recovered. What do these results show?

Patients given an antiviral within 48 hours of their first symptoms stayed in hospital 3 days on average; patients treated later stayed 6 days. What do these data support?

Of 250 diphtheria patients given an antitoxin, 15 were still ill after 10 days; of 250 given usual care, 95 were still ill. A student claims the antitoxin cures everyone. Why do the data not support that?