Stanford, Calif.

DESPITE all the attention given to anthrax and smallpox and potential weapons of mass destruction, pandemic influenza is probably the world’s most serious near-term public health threat. If a strain similar in effect to the 1918 Spanish flu (which killed tens of millions of people worldwide) emerges in the next several years, it is highly likely that an effective vaccine will not be available during the pandemic’s first wave, that we won’t have enough antiviral drugs for large-scale prophylactic use, and that hospitals will be too overwhelmed to treat most cases.

Consequently, as in 1918, we will need to combine medical efforts with voluntary and forced social changes — closing schools and churches, canceling public gatherings, keeping workers at home — to hinder the flu’s spread. Our government must draw up a plan for educating the public about effective nonpharmaceutical interventions like hand washing and face protection like masks.

A prerequisite for doing so is determining the biggest culprit in spreading influenza: droplet transmission, in which an infected person sneezes or coughs directly into the mouth, nose or eyes of someone who is susceptible); contact transmission, in which virus is transferred via hands either directly, say, through a handshake, or indirectly through an object like a doorknob; and aerosol transmission, in which evaporated virus-containing particles are inhaled.

Remarkably, this issue has not been resolved: the Department of Health and Human Services’ Pandemic Influenza Plan states that “the relative clinical importance of each of these modes of transmission is not known.” As a result, the government enthusiastically endorses frequent hand washing — which would reduce contact transmission, and costs nothing — but remains noncommittal about face protection. While the government says that it might be beneficial, it doesn’t make respirators or masks available. Yet face protection would guard against aerosol and droplet transmission, and even reduce contact transmission by making it difficult to place fingers into one’s mouth or nose.