Friday, April 28, 2006

The mask problem

As noted previously, the "mask question" was kicked over to the Institute of Medicine (part of the National Academies of Science). The report came out yesterday.
If a worldwide flu epidemic strikes, face masks should be considered a defense of last resort since there's little evidence about whether the masks available to the average person or most health care workers can prevent influenza infection, the Institute of Medicine said Thursday.


Health workers use masks — simple surgical masks or better-filtering ones called N95 respirators — mostly to keep from breathing their own germs into open wounds or onto otherwise vulnerable patients. But certain filtering masks also can protect wearers from specific respiratory diseases, such as tuberculosis.

The masks are supposed to be used once and discarded. Anticipating a staggering demand if the bird flu or some other super-strain of influenza sparks the next pandemic, federal health officials asked the IOM to determine whether there are masks that could be reused safely, to conserve supplies. (Lauran Neergaard, AP)
Do masks work for influenza? No one knows:

The first question is whether different masks really block influenza, noted the IOM panel — a question the government didn't ask, but that the scientific advisers said should be studied, urgently.

"Just to double-emphasize: We don't have good data to make a decision about how effective they are or are not," said panel co-chair Dr. Donald Burke of Johns Hopkins University.
It would seem a no-brainer that using a mask is better than not using one. But that depends on whether the mask affects your behavior, for example, encouraging you to do things you wouldn't do without it, like go into crowds. As we have noted here a number of times, we don't understand completely how flu gets around, specifically the relative importance of object to hand to mouth/eye versus large (quickly settling) droplets from coughs or sneezes versus tiny droplets that remains suspended for hours or days.

Filtering masks also have to be professionally fitted to the user's face (forget it if you have a beard). Assuming the mask works for flu (an open question), its outside remains contaminated, so it has to be handled and disposed of carefully. The IOM panel was reluctant to discourage people from wearing a mask because it honestly didn't know their value.

Masks thus join Tamiflu and the current experimental vaccines as methods absorbing a lot of resources but of unproven effectiveness. Better to invest in the harder but proven methods of strengthening the public health system and its social service counterparts. Those work, pandemic or no pandemic.

Better to bite the bullet than to wait for a magic one.