Location in which encounters took place. The average number of encounters per participant recorded in the paper diary within each age category was described for each of the following locations: 'work', 'travel', 'social', 'shop', 'home' and 'other' on Wednesday (a), Friday (b) and Sunday (c). It should be noted that while averages are reported, the number of observations within each age group upon which these figures are based varies between 1 (70-79) and 22 (40-49). As can be seen from comparison of locations reported on Wednesday (a) and Sunday (c), a predictable shift from predominance of work-based mixing to home-based and social encounters is observed over the weekend. On Wednesdays (a), however, levels of physical contact in the home environment are almost equivalent to those reported in the workplace (data not shown). Wednesday (a) and Friday (b) are more similar.