Epidemiological information: E. coli O157:H7 illness in the Maritimes and Ontario

18 January 2013

What is epidemiology?

Epidemiology is the study of disease in a population. Epidemiologists, or "disease detectives," use surveillance systems to identify those who are sick and confirm that the sick people are part of this event. They then gather information from the people who got sick and review the clues from all parts of the investigation that might reveal the cause of the illness event.

The figure and table below form part of the epidemiological investigation into this outbreak. An "epi curve" (Figure 1) is a valuable reference tool in any epidemiological investigation. An epi curve shows when cases begin, when they peak, and when they trail off. Certain details of the people who got sick (Table 1) also help epidemiologists as they work to solve the questions involved in foodborne illness.

Figure 1. Number of people infected with the outbreak strain of E. coli

Figure 1
Text equivalent for figure 1
Table 1. People confirmed to be infected with the outbreak strain of E. coli O157, by date of illness onset
Date of Onset Number of Cases
12-Dec 0
13-Dec 0
14-Dec 0
15-Dec 0
16-Dec 0
17-Dec 0
18-Dec 0
19-Dec 0
20-Dec 0
21-Dec 0
22-Dec 1
23-Dec 9
24-Dec 3
25-Dec 0
26-Dec 5
27-Dec 1
28-Dec 2
29-Dec 1
30-Dec 1
31-Dec 1
01-Jan 0
02-Jan 3
03-Jan 1
04-Jan 0
05-Jan 1
06-Jan 0
07-Jan 0
08-Jan 0
09-Jan 1
10-Jan 0
11-Jan 0
12-Jan 0
13-Jan 0
14-Jan 0
15-Jan 0
16-Jan 0
17-Jan 0
Note: It can take several weeks from the time a person becomes ill to when this illness is reported and testing confirms a link to the outbreak.
Table 1: At a Glance
Outbreak status Ongoing
Case count 30
Provinces/Territories 3
Deaths 0
Hospitalizations* 13
Cases with Hemolytic Uremic Syndrome (HUS) 1
Gender (m:f) 15:15
Age range in years 1-83
Recall Yes

* Verification conducted as part of the investigation has confirmed that 13 cases were hospitalized not 14, as previously noted.

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