| Date | November 2015 | Marks available | 2 | Reference code | 15N.3.HL.TZ0.7 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Compare | Question number | 7 | Adapted from | N/A |
Question
The bacterium Escherichia coli is responsible for over 70 000 cases of illness each year in the US. More than half of these cases are due to transmission of the bacteria in food, particularly from ground beef in undercooked burgers. Epidemiologists collected evidence from 183 outbreaks of food poisoning between the years 1982 and 2002 and identified the food responsible for the outbreak. They divided the foods into dairy products, fruit and vegetables, beef, ground beef (beef which has been minced) and other foods. In some cases they were unable to identify the food that had caused the outbreak. The results are displayed in the bar chart.
State the number of years during the study when contaminated dairy products caused food poisoning.
Compare the outbreaks of food poisoning in 1989 and 1994.
Suggest two reasons for these changes.
Explain how pasteurization may have prevented food poisoning by dairy products.
Markscheme
6 (years) (units not required)
a. total number of outbreaks of food poisoning (much) greater in 1994/ changed from 1 to 23;
b. more unknown outbreaks in 1994 than in 1989;
c. food poisoning in 1994 due to ground beef/beef/fruit and vegetables/other sources which did not occur in 1989;
d. greatest increase in food poisoning due to ground beef;
e. no food poisoning due to dairy products in either year / increase in food poisoning from other sources from 1989 to 1994;
a. increase in range of foods available;
b. increase in fast food outlets (short time of cooking) / change in preparation methods / OWTTE;
c. increase in technological advances to analyse outbreaks / more awareness (of occurrence of contaminations) / better data collection / OWTTE;
d. increase in bacterial resistance;
a. milk is quickly heated;
b. to high temperatures then rapidly cooled down;
c. this kills harmful bacteria;
Examiners report
Candidates handled the data without problems although some of the comparisons were weak. Some gave very vague reasons for the changes such as more food, more bacteria, etc., without any explanation of why these changes could have occurred in 5 years. The most common answers were related to food preparation and types of food available. Most had some knowledge about pasteurization, but few included sufficient detail as to timing.
Candidates handled the data without problems although some of the comparisons were weak. Some gave very vague reasons for the changes such as more food, more bacteria, etc., without any explanation of why these changes could have occurred in 5 years. The most common answers were related to food preparation and types of food available. Most had some knowledge about pasteurization, but few included sufficient detail as to timing.
Candidates handled the data without problems although some of the comparisons were weak. Some gave very vague reasons for the changes such as more food, more bacteria, etc., without any explanation of why these changes could have occurred in 5 years. The most common answers were related to food preparation and types of food available. Most had some knowledge about pasteurization, but few included sufficient detail as to timing.
Candidates handled the data without problems although some of the comparisons were weak. Some gave very vague reasons for the changes such as more food, more bacteria, etc., without any explanation of why these changes could have occurred in 5 years. The most common answers were related to food preparation and types of food available. Most had some knowledge about pasteurization, but few included sufficient detail as to timing.
