Article No. 5 - Vol. 28, No. 4 - December 2009 Print E-mail

Epidemiological Calendar 2010

The uses of surveillance data include the description and comparison of disease patterns using the person, place, and time variables. In particular, examples of the use of the time variable can be found in the earliest known epidemiological studies. For example, in a report on the 1847 influenza epidemic in London, William Farr presented data collected by week and easily calculated the excess of mortality due to influenza in different periods of the year. (1)

The discussion among statisticians from various disciplines on the use of specific time units seems to have been a constant at the beginning of the 20th century. In May 1925, a document was presented to the British Royal Statistical Society, which argues for the first time that a period of time shorter than the calendar month (the week) is necessary as a “principle of division” of the year for purposes of vital statistics analysis. (2)

Today, there is an international consensus about the use of a standard time period to group deaths or other epidemiological events. This period is generally the week and is known as the epidemiological week. The division of the 365 days of the year in 52 epidemiological weeks is known as the epidemiological calendar. It is a way to standardize the time variable for the purpose of epidemiological surveillance.

The importance of this division and above all of the use of the epidemiological week relies on the fact that it allows for the comparison of epidemiological events that occurred in a given year or period of a year, with that of previous years. It also facilitates the comparison between countries.

Epidemiological weeks start on a Sunday and end on a Saturday; The first epidemiological week of the year ends, by definition, on the first Saturday of January, as long as it falls at least four days into the month, even if it means that this first week starts in December.

The 2010 Epidemiological Calendar begins on 3 January 2010. To illustrate the previous point, the following correspond to the first epidemiological weeks of a few consecutive years:

2005 January 2 – January 8, 2005

2006 January 1 – January 7, 2006

2007 December 31, 2006 – January 6, 2007

2008 December 30, 2007 – January 5, 2008

2009 January 4 – January 10, 2009

2010 January 3 – January 9, 2010

 

EW

Mo

Sun

Mon

Tue

Wed

Thu

Fri

Sat

Mo

1

Jan

3

4

5

6

7

8

9

Jan

2

Jan

10

11

12

13

14

15

16

Jan

3

Jan

17

18

19

20

21

22

23

Jan

4

Jan

24

25

26

27

28

29

30

Jan

5

Jan

31

1

2

3

4

5

6

Feb

6

Feb

7

8

9

10

11

12

13

Feb

7

Feb

14

15

16

17

18

19

20

Feb

8

Feb

21

22

23

24

25

26

27

Feb

9

Feb

28

1

2

3

4

5

6

Mar

10

Mar

7

8

9

10

11

12

13

Mar

11

Mar

14

15

16

17

18

19

20

Mar

12

Mar

21

22

23

24

25

26

27

Mar

13

Mar

28

29

30

31

1

2

3

Apr

14

Apr

4

5

6

7

8

9

10

Apr

15

Apr

11

12

13

14

15

16

17

Apr

16

Apr

18

19

20

21

22

23

24

Apr

17

Apr

25

26

27

28

29

30

1

May

18

May

2

3

4

5

6

7

8

May

19

May

9

10

11

12

13

14

15

May

20

May

16

17

18

19

20

21

22

May

21

May

23

24

25

26

27

28

29

May

22

May

30

31

1

2

3

4

5

Jun

23

Jun

6

7

8

9

10

11

12

Jun

24

Jun

13

14

15

16

17

18

19

Jun

25

Jun

20

21

22

23

24

25

26

Jun

26

Jun

27

28

29

30

1

2

3

Jul

27

Jul

4

5

6

7

8

9

10

Jul

28

Jul

11

12

13

14

15

16

17

Jul

29

Jul

18

19

20

21

22

23

24

Jul

30

Jul

25

26

27

28

29

30

31

Jul

31

Aug

1

2

3

4

5

6

7

Aug

32

Aug

8

9

10

11

12

13

14

Aug

33

Aug

15

16

17

18

19

20

21

Aug

34

Aug

22

23

24

25

26

27

28

Aug

35

Aug

29

30

31

1

2

3

4

Sep

36

Sep

5

6

7

8

9

10

11

Sep

37

Sep

12

13

14

15

16

17

18

Sep

38

Sep

19

20

21

22

23

24

25

Sep

39

Sep

26

27

28

29

30

1

2

Oct

40

Oct

3

4

5

6

7

8

9

Oct

41

Oct

10

11

12

13

14

15

16

Oct

42

Oct

17

18

19

20

21

22

23

Oct

43

Oct

24

25

26

27

28

29

30

Oct

44

Oct

31

1

2

3

4

5

6

Nov

45

Nov

7

8

9

10

11

12

13

Nov

46

Nov

14

15

16

17

18

19

20

Nov

47

Nov

21

22

23

24

25

26

27

Nov

48

Nov

28

29

30

1

2

3

4

Dec

49

Dec

5

6

7

8

9

10

11

Dec

50

Dec

12

13

14

15

16

17

18

Dec

51

Dec

19

20

21

22

23

24

25

Dec

52

Dec

26

27

28

29

30

31

1

Jan

 

References

(1) Langmuir AD. William Farr: Founder of Modern Concepts of Surveillance. International Journal of Epidemiology 1976; 5(1):13-18

(2) Watkins H. Time counts: the story of the calendar. New York, Philosophical Library. 1954