|Study ID||Country||Aim of the study||Study design||Population||Sample size||Type of infection||Method of identifying infection||Relevant outcomes||Findings|
|Abd ||Iraq||To identify the risk factors predisposing to SARS-CoV-2 infection||Retrospective cross-sectional survey||General public||N = 348 hospitalised COVID-19 cases & 348 hospitalised non-COVID-19 patients||SARS-CoV-2||Confirmed in the hospital (no details provided)||Risk factors for SARS-CoV-2 acquisition||
Amongst confirmed COVID-19 cases, 66 (18.96%) reported washing their hands “healthily”, whereas 148 (42.52%) reported doing so sometimes, compared to 94 (27.01%) and 134 (38.50%) non-COVID-19 patients, respectively.|
There was a statistically significant association between COVID-19 infection and hand washing (p < 0.001).
|Badri et al. ||USA||To identify behaviours and evaluate trends in COVID-19-mitigating practices in a predominantly Black and Hispanic population, to identify differences in practices by self-reported ethnicity, and to evaluate whether federal emergency financial assistance was associated with SARS-CoV-2 acquisition||Retrospective cross-sectional survey||General public||N = 209 individuals who tested positive for SARS-CoV-2 & 105 who tested negative||SARS-CoV-2||Laboratory confirmed||Risk factors for SARS-CoV-2 acquisition||Frequent use of ABHR was associated with lower odds of infection (aOR: 0.26; 95% CI: 0.13, 0.52), but frequent hand washing showed no significant effect (aOR: 0.55; 95% CI: 0.21, 1.44).|
|Castilla et al. ||Spain||To evaluate risk factors and measures to prevent influenza infection in the community||Retrospective case-control study||General public||N = 481 influenza outpatients & 481 controls||Influenza||Laboratory confirmed||Risk factors for influenza acquisition||The frequency of hand washing 5–10 times (aOR: 0.87; 95% CI: 0.54, 1.39; p = 0.56), and > 10 times (aOR: 0.98; 95% CI: 0.59, 1.64; p = 0.94), the use of ABHR (aOR: 1.36; 95% CI: 0.85, 2.19; p = 0.2) and hand washing after touching contaminated surfaces (aOR: 0.70; 95% CI: 0.44, 1.11; p = 0.13) had no significant protective effect.|
|Doshi et al. ||Bangladesh||To identify household-level factors associated with influenza among young children in a crowded community in Dhaka||Prospective case-control study||Pre-school children||N = 145 households of influenza paediatric cases & 341 control households||Influenza||Laboratory confirmed||Risk factors for influenza acquisition||
The mean hand washing frequency during a 5-hour observation period was similar between case (0.64 events) and control (0.63 events) households (p = 0.87). Mean daily soap consumption per capita was 2.92 and 2.93 in the case and control households, respectively (p = 0.92).|
Almost all case (97%) and control (99%) households had water present at the primary hand washing location, but 22% of case households and 29% of control households had soap present before it was provided for soap consumption measurement (p = 0.08).
|Doung-ngern et al. ||Thailand||To evaluate the effectiveness of personal protective measures against SARS-CoV-2 infection in public||Retrospective case-control study||General public||N = 211 cases & 839 controls||SARS-CoV-2||Laboratory confirmed||Risk factors for SARS-CoV-2 transmission (secondary attack rates)||A significant, negative association was found between risk for SARS-CoV-2 infection and washing hands “often” (aOR: 0.33; 95% CI: 0.13, 0.87) or “sometimes” (aOR: 0.34; 95% CI: 0.14, 0.81); p = 0.045.|
|Godoy et al. ||Spain||To investigate the effectiveness of non-pharmacological interventions in preventing cases of influenza requiring hospitalization||Retrospective case-control study||General public||N = 813 hospitalized influenza cases & N = 2274 controls||Influenza||Laboratory confirmed||Protective factors against influenza acquisition||The frequency of hand washing 5–10 times (aOR: 0.65; 95% CI: 0.52, 0.84; p = 0.001) and > 10 times (aOR: 0.59; 95% CI: 0.44, 0.79, p < 0.001) and hand washing after contact with contaminated surfaces (aOR: 0.65; 95% CI: 0.50, 0.84; p = 0.001) were protective factors and were dose-responsive (p < 0.001). ABHR showed no significant protective effect (aOR: 0.82; 95% CI: 0.65, 1.02; p = 0.08).|
|Karout et al. ||USA||To determine the prevalence, level of COVID-19 risk perception attitude and preventive behaviour implemented by the Latino population in the USA||Prospective cross-sectional survey||General public||N = 410 asymptomatic Latino adults||SARS-CoV-2||Laboratory-confirmed||Preventive factors associated with SARS-CoV-2 acquisition||Participants who tested positive (n = 76; 18.5%) were significantly less likely to use ABHR and wash hands compared with participants who tested negative (p < 0.001).|
|Lau et al. ||China||To delineate the distribution of different sources of SARS transmission, identify the undefined source group and to identify relevant risk and protective factors associated with contracting SARS||Retrospective case-control study||General public||N = 330 suspected SARS cases with undefined infection sources & 660 controls||SARS-CoV-1||SARS case definition criteria||Risk and preventive factors associated with SARS-CoV-1 acquisition||Frequent hand washing (more than 10 times a day) was a significant protective factor (OR: 0.58; 95% CI: 0.38, 0.87; p = 0.008).|
|Lio et al. ||China||To determine the risk and protective factors for COVID-19 infection at the individual level, with a specific emphasis on personal behaviours such as mask use, the number of gatherings, and HH practices||Retrospective case-control study||General public||N = 24 hospitalised COVID-19 patients & 1113 control participants who completed quarantine after travelling from COVID-19 high-risk foreign country||SARS-CoV-2||Laboratory-confirmed||Risk and preventive factors associated with SARS-CoV-2 acquisition||
Compared to the non-infected individuals, those with SARS-CoV-2 infection were significantly less likely to wash hands after contact with individuals who had respiratory symptoms (50% vs. 95.3%; p = 0.005), but not after contact with suspected or confirmed COVID-19 patients (50% vs. 95.2%; p = 0.057).|
Hand washing after outdoor activity (aOR: 0.021; 95% CI: 0.003, 0.134; p < 0.005), hand washing before touching the mouth and nose area (aOR: 0.303; 95% CI: 0.114, 0.808; p < 0.05) were found to be independent factors for COVID-19 infection.
Amongst infected individuals, 16.7% reported always washing hands for over 20 seconds each time, compared with 31.9% in the non-infected group (p = 0.125).
|Liu et al. ||USA||To understand the risk of SARS-CoV-2 transmission from a paediatric primary index case to household contacts living in Los Angeles County||Prospective cohort study||Children||N = 15 paediatric index cases & 50 household contacts||SARS-Cov-2||Laboratory-confirmed||Risk factors for SARS-CoV-2 transmission (secondary attack rates)||
Overall secondary attack rates were 34% (95% CI: 22, 48%).|
Transmission was significantly lower in households with increased hand washing or ABHR use compared with those who did not report increased hand washing or ABHR use (19%; 95% CI: 9, 36) vs. 58%; 95% CI: 36, 77; p = 0.01).
|Speaker et al. ||USA||To compare the social behaviours of individuals who were tested positive for COVID-19 relative to non-infected individuals||Retrospective case-control study||General public||N = 113 COVID-19 cases & 226 controls||SARS-Cov-2||Laboratory confirmed||Risk factors for SARS-CoV-2 acquisition||67% of cases and 63% of controls reported always washing hands or using ABHR after possible exposures (p = 0.24). 75% of cases and 74% of controls reported always washing hands for at least 20 seconds (p = 0.60).|
|Wilson-Clark et al. ||Canada||To determine characteristics associated with the transmission of SARS within households||Retrospective cross-sectional survey||General public||N = 74 SARS-affected households||SARS-Cov-1||SARS case definition criteria||Risk factors for household transmission of SARS-CoV-1||Failure to wash hands after caring for ill person (RR: 3.46; 95% CI: 1.10, 10.92) and not always washing hands after changing a diaper (RR: 3.94; 95% CI: 1.28, 12.10) were associated with an increased risk of transmission.|
|Torner et al. ||Spain||To investigate the effectiveness of non-pharmaceutical interventions in preventing cases of influenza in children in the community setting in 2009 pandemic and 2010–2011 post pandemic/seasonal epidemic||Retrospective case-control study||Children||N = 239 confirmed paediatric influenza outpatients & 239 controls||Influenza||Laboratory-confirmed||Risk factors for influenza acquisition||
Hand washing more than 5 times per day (aOR: 0.62; 95% CI: 0.39, 0.99; p = 0.04) was the only statistically significant protective factor.|
For 5–17 age group, there was a negative association for influenza infection for both washing more than 5 times per day (aOR: 0.47; 95% CI: 0.22, 0.99; p = 0.04) and hand washing after touching contaminated surfaces (aOR: 0.19; 95% CI: 0.04, 0.86; p = 0.03).
For the 0–4 years group there was no significant association for washing hands more than 5 times per day (aOR: 0.91; 95% CI: 0.46, 1.78; p = 0.77) nor for hand washing after touching contaminated surfaces (aOR: 1.06; 95% CI: 0.44, 2.56; p = 0.77).
|Wu et al. ||China||To compare exposures of unlinked, probable SARS patients with community-based matched controls||Retrospective case-control study||General public||N = 94 probable SARS patients & N = 281 controls||SARS-Cov-1||Laboratory confirmed||Risk and preventive factors associated with SARS-CoV-1 acquisition||
Always washing hands when returning home was a protective factor (OR: 0.3; 95% CI: 0.2, 0.7; p = 0.003).|
No significant association was found for always washing hands before eating (OR: 0.6; 95% CI: 0.3, 1.1; p = 0.11) or after using restrooms (OR: 0.5; 95% CI: 0.2, 1.2; p = 0.10).
|Xie et al. ||China||To quantify exposure patterns, transmission characteristics, and the clinical spectrum of SARS-CoV-2 infection||Retrospective cohort study||General public||N = 20 index patients hospitalized with severe COVID-19 & 79 of their household contacts||SARS-Cov-2||Laboratory confirmed||Risk factors for SARS-CoV-2 transmission||Hand washing ≥5 times/day was associated with reduced infection risk (52.8% vs.76.9%, p = 0.04).|
|Zhang et al. ||China||To assess risk factors associated with household transmission of pandemic H1N1 from self-quarantined patients in Beijing||Retrospective case-control study||General public||N = 54 case households & 108 control households||Influenza||Laboratory confirmed||Risk factors for influenza transmission||Hand washing ≥3/day was related to the household transmission of pandemic H1N1 from self-quarantined patients (OR: 0.71; 95% CI: 0.48, 0.94; p = 0.05).|