Surprising new CDC guidance.
By Betsy Todd, MPH, RN, nurse epidemiologist and AJN clinical editor. Published: March 13, 2020. New posts will appear on this blog about aspects of the pandemic as the situation and our knowledge about the virus continue to evolve.
For nurses, the biggest news this week wasn’t the declaration of the COVID-19 epidemic as an official pandemic. It was the CDC’s release on March 10 of new interim infection prevention and control recommendations for COVID-19.
Many of us were taken aback to read the new document, which recommends the use of regular surgical face masks instead of N95s and the routine placement of patients suspected or confirmed of having COVID-19 infection in private rooms with the door closed instead of housing them in a negative pressure isolation room (which are always in short supply).
Unfortunately, without first acknowledging the concerns such a change from longstanding infection control practice might occasion among nurses and others, the CDC presented it as necessary due to an N95 shortage, stating, “When the supply chain is restored, facilities . . . should return to use of respirators for patients with known or suspected COVID-19.”
While it’s clear the CDC could have crafted this message more carefully, are caregivers being thrown under the bus just because the supply chain is stressed? Maybe not entirely. The CDC does at least provide some evidence to support mask use in the Background section of the new recommendations.
Are masks or respirators our only protection?
Infection prevention professionals have long referred to a “hierarchy of controls,” ranked according to their reliability and effectiveness. Engineering and administrative controls are considered the most effective infection prevention measures, because they are “built into” physical systems and protocols (HEPA filters in HVAC systems, needleless connectors, safety syringes). Personal protective equipment (PPE) is considered the least effective preventive measure because it’s dependent upon proper use (do you tie your gown at the neck?), correct fit/placement, and consistent use.
Mode of transmission.
A growing body of evidence continues to suggest that this coronavirus is spread primarily by droplets, and that “the contribution of . . . aerosols or droplet nuclei to close proximity transmission is currently uncertain.” However, we assume these could be produced during aerosol-generating procedures like suctioning or intubation. In fact, the new CDC document specifies that N95 masks should be worn on these occasions. But it seems pretty clear at this point, after patients with COVID-19 have been cared for in a variety of settings, that the virus particles don’t travel long distances on air currents in the way that measles or tuberculosis droplets can.
Research comparing N95s with surgical masks.
Direct comparisons of N95 respirators with surgical masks when caring for patients with influenza have found no significant difference in influenza incidence. It seems clear that regular surgical masks, though designed to contain the wearer’s droplets, also provide protection against infections transmitted by droplets.
This begs the question: why do CDC and WHO experts tell people NOT to wear surgical face masks for protection from viruses when they are out and about in the street?
While I think we need a very clear answer from the experts going forward, it seems that there are two issues: First, that in times of increased illness around the globe, caregivers have by far the greatest need (often, a life-and-death need) for protection, and therefore should have priority in accessing masks.
Second, it really is a dubious strategy to wear a mask for protection against something that can be transmitted only via pretty close face-to-face contact with an infected person. Walking down the street or sitting on a bus simply does not present an appreciable level of droplet transmission risk. Once you add on improper use—mask moisture from extended wear, touching the mask repeatedly, wearing it hanging like a necklace for a break—you are likely to be increasing your risk of infection, not decreasing it.
Amid the growing number of cases of community transmission in Seattle, Santa Clara, and the New York City area in recent weeks, I suspect that other than possibly during household transmission of COVID-19, many more cases are being acquired indirectly through “touch” contamination than by direct inoculation onto mucous membranes. Masks not only won’t help you there—they are likely to give such a false sense of security that you pay little attention to where your hands go or how often you clean them.
The CDC owes us some clarity regarding protective gear for droplet vs. airborne isolation precautions, and we likely will see that in the near future.
Meanwhile, a few additional takeaways:
- The new recommendations do emphasize that N95s should be worn during aerosol-generating procedures and for the care of other patients with infections documented to transmit via the airborne route such as tuberculosis, measles, and varicella.
- The recommendation of a private room with the door closed is, like the surgical mask recommendation, a recognition of the fact that this virus appears to be dependent upon the droplet, not airborne, mode of transmission.
- Eye protection is essential with either mask. A good additional measure of protection when wearing a surgical mask instead of a “just-in-case-something-gets-airborne” N95 respirator when caring for patients with COVID-19 is to wear a full-face face shield that covers both your eyes and the mask.
- As part of their Pandemic Planning series, the National Institute for Occupational Safety and Health (NIOSH) has published an excellent, detailed guide to the reuse and extended use of N95s when these respirators are in short supply. (Note that a decision to incorporate the reuse or extended use of N95s into your facility’s respiratory protection program is NOT an individual decision. The determination usually is made by the infection prevention team, often in collaboration with the local or state department of health.)