Cyclosporiasis Outbreak Investigations: Epi Curves — United States, 2013 (Final Update)

Epi Curves

The illnesses can be visually described with a graph showing the number of persons who became ill each week. This graph is called an epi curve.

Figure 1. Confirmed Cyclosporiasis Cases, by Groups of States, June—August 2013*

* N=631. Outbreak-associated cases are defined as laboratory-confirmed Cyclospora infection in a person with symptom onset (reported or estimated) between June 1 and August 31, 2013, and no known travel outside the United States or Canada in the 14 days prior to symptom onset.

In the graph above, the number of persons who became ill each week is plotted separately for persons who fell ill in Iowa and Nebraska, in Texas, and in all other states combined, for those cases for which onset of illness dates were available.

The cases reported by Iowa and Nebraska peaked in mid-June, and then decreased to low levels. Cases reported from Texas increased more slowly, reaching a peak in late June-early July, before declining moderately. Cases reported in other parts of the country occurred in lower numbers through June and July, without a distinct peak. This suggests that there was more than one outbreak of cyclosporiasis during June–August 2013 in the United States.

Figure 2. Confirmed Cyclosporiasis Cases by Week of Illness Onset, United States*

*A total of 645 reported cases not know to be international travel associated had onset of illness between April 28 and September 28, 2013. Of these reported cases, 631 were outbreak associated. Outbreak-associated cases are defined as laboratory-confirmed Cyclospora infection in a person with symptom onset (reported or estimated) between June 1 and August 31, 2013, and no known travel outside of the United States or Canada in the 14 days prior to symptom onset. Reported cases of cyclosporiasis in the United States have returned to baseline levels, as shown by the green line; therefore, it is likely that the outbreaks identified during June–August 2013 have ended. The number of reports of persons with illness increased beginning in June and returned to baseline in mid-to-late August.

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