Hand hygiene. Respondents were asked to indicate frequencies of use of four hand hygiene practices over the three days prior to interview: hand washing after sneezing, coughing and touching nose; hand washing after returning home, use of liquid soap for hand washing, and hand washing after touching common objects. Responses were on a 4-point scale of frequency: 1 ''never'', 2 ''sometimes'', 3 ''usually'' and 4 ''always''. Cronbach's a was 0.62 (Table S1 ).