Figure 3From: Geographical differences in whooping cough in Catalonia, Spain, from 1990 to 2010 Structural changes (SC) in the four-week periods in urban and rural counties of Catalonia, 1990–2010. Each year was distributed in 13 four-week periods. a. Rural counties. SC occurred in the following four-week periods: 4th in 1993, 7th in 1996 and 3rd in 2005. b. Urban counties. SC occurred in the following four-week periods: 5th in 1993, 9th in 1996 and 8th in 2007.Back to article page