The scientific jury is not unanimous on this issue, but it looks like wearing a surgical mask matters enough to recommend their use under certain conditions, and their use, or the use of a more effective respirator, is recommended under certain conditions. In my experience, face masks are routinely distributed patients arriving in urgent care centers and similar when influenza is cranked up in the community.
Washing your hands a lot AND using a face mask seems to reduce transmission within a household where there is a sick person. This practice probably works, and is standard and recommended, for health care workers. People wandering around on the landscape who don’t have the flu or other virus probably don’t get real protection from wearing a surgical mask, but sick people probably transmit less, if for no other reason than it reduces the amount of nose/mouth-to-hand transfer of viral kooties.
Most of the research on this topic was done during either the H1N1 or SARS hyperawareness period, as expected, but I’ve not seen anything contradictory since. Here are some examples:
” Face masks and hand hygiene combined may reduce the rate of ILI and confirmed influenza in community settings. These non-pharmaceutical measures should be recommended in crowded settings at the start of an influenza pandemic.” (Aiello et al 2012)
“This is the first RCT on mask use to be conducted and provides data to inform pandemic planning. We found compliance to be low, but compliance is affected by perception of risk. In a pandemic, we would expect compliance to improve. In compliant users, masks were highly efficacious. A larger study is required to enumerate the difference in efficacy (if any) between surgical and non-fit tested P2 masks.” (MacIntyre et al, 2008)
“Hand hygiene with or without facemasks seemed to reduce influenza transmission, but the differences compared with the control group were not significant. In 154 households in which interventions were implemented within 36 hours of symptom onset in the index patient, transmission of RT-PCRâ€“confirmed infection seemed reduced, an effect attributable to fewer infections among participants using facemasks plus hand hygiene (adjusted odds ratio, 0.33 [95% CI, 0.13 to 0.87]). Adherence to interventions varied.” (Cowling et al. 2009)
The CDC is not sure if asymptomatic non healthcare workers get much benefit, but they don’t say not to do it. They do say to get your vaccinations, and if you get sick, get medical attention which might include an anti-viral. Health care workers are told (by CDC) to always have a mask or respirator if they are within 6 feet of a sneezy coughy diseased person.