Physical interventions to interrupt or reduce the spread of respiratory viruses: a systematic review
idemics can occur. Mathematical models estimate that about 36 000 deaths and 226 000 admissions to hospital in the United States annually are attributable to influenza, and with incidence rates as high as 50% during major epidemics worldwide, respiratory viruses strain health services, are responsible for excess deaths, and result in massive indirect costs owing to absenteeism from work and school. Concern is now increasing about serious pandemic viral infections. In 2003 an epidemic of the previously unknown severe acute respiratory syndrome (SARS) caused by a coronavirus affected about 8000 people worldwide, with 780 deaths (disproportionately high numbers were in healthcare workers), and causing a social and economic crisis, especially in Asia. A new avian influenza pandemic caused by the H5N1 virus strain threatens greater catastrophe. High viral load and high viral infectiousness probably drive virus pandemics,7 hence the need for interventions to reduce viral load. Mounting evidence suggests, however, that single measures, particularly the use of vaccines or antivirals, will be insufficient to interrupt the spread of influenza. Agent specific drugs are also not available for other viruses. A recent trial found hand washing to be effective in lowering the incidence of pneumonia in the developing world.w1 Clear evidence has also shown a link between personal (and environmental) hygiene and infection.11 We systematically reviewed the evidence for the effectiveness of combined public health measures such as personal hygiene, distancing, and barriers to interrupt or reduce the spread of respiratory viruses. We did not include vaccines and antivirals because these have been reviewed.