“…Causes of transmission in the eligible studies were reported as person-to-person transmission, contaminated water and food, and problems in practice (Tables 2 and 4). The following studies (n = 12) did not report or could not identify the cause of the outbreaks: 5 studies on influenza viruses, 2 on non-typeable Haemophilus influenzae, 1 on hepatitis C virus, 1 on C. difficile, 1 on adenovirus, 1 on norovirus, and 1 on RSV and HMPV [14,27,29,30,32,36,40,42,44,45,48,50]. The most commonly reported route of transmission was person-to-person [17, 22-24, 26, 31, 33, 35, 38, 41, 43, 46, 47, 49].…”