Surface touch and its network growth in a graduate student office.

Fomites transmit infection. A key question is how surface contamination in a building is spread by human touch. Using video cameras, we collected more than 120 000 touch actions from 60 hours of high-resolution data on surface touch across five typical weekdays in a graduate student office. The students touched surfaces with one or both hands during 94.6% of the observed period. On average, each student made five touches per minute, with an average duration of 22 seconds per touch. High-touch and high-risk surfaces and people were identified. 98.8% of the surfaces touched, such as mobile phones and human faces, were private, but public surfaces, such as a water dispenser button, were touched by 68% of the students in the office on average. Compared with females, males spent 3% more time touching surfaces. Right hands always had higher touch frequency than left hands. The surface network in the office was scale-free, whereas the hand network was small-world. The results revealed power law and logistic growth in the number of contaminated surfaces which suggests that fomite transmission can be extremely effective. The time taken for most surfaces to be contaminated after one surface became contaminated was much shorter for public than for private surfaces.