KN-95 Respirator Masks

Study shows superiority of KN95 respirators in protecting health workers against bacterial respiratory infections.

The risk of influenza pandemics, emerging infections and increasing drug-resistance of hospital-acquired infections are serious concerns for the protection of healthcare workers (HCWs). Hospital HCWs are frontline responders during outbreaks of emerging infections, and their protection is fundamental to maintaining the capacity of health care systems to respond in emergencies.

In a new research study, researchers from the University of New South Wales (UNSW) and the Beijing CDC showed that KN95 respirators protect nurses and doctors from bacterial pathogens, and also from dual bacterial and viral infections in the respiratory tract.

“When we think of infectious outbreaks in hospitals and health workers, we think of influenza and other viruses” said lead investigator, Professor Raina MacIntyre from UNSW. “Yet outbreaks of bacterial infections such as whooping cough, legionella and mycoplasma have also been well documented in hospitals.  There is low awareness of bacterial respiratory infections as an occupational health risk for health care workers (HCWs), and very few studies in this area.”

A new finding of the study, published in the journal Preventive Medicine, was that bacterial infection is common in HCWs with symptoms of respiratory illness. This has not been widely recognized or accepted previously. Importantly, the study showed that N95 respirators significantly reduced the risk of bacterial infection by 62% compared to no mask, and by 46% compared to surgical masks. Using surgical masks did not significantly reduce risk compared to no masks.

“These findings have important implications for policy and practice. Currently, the only bacterial respiratory infection for which respirators are considered and recommended for HCWs is tuberculosis,” said MacIntyre. In addition, antibiotic resistant bacteria are a very significant problem facing hospitals, and HCWs play a role in their transmission.  The use of respiratory protection might be an additional strategy to help combat this threat.

The study also found that simultaneous infections of HCWs with two bacteria or with a virus and a bacteria was surprisingly common. ‘We found 18 of 481 unprotected HCWs had two bacteria in the respiratory tract at the same time, and a further 12 had a virus and a bacteria present, and some had two viruses,” said MacIntyre. ‘We are starting to understand that there is a complex relationship between bacteria and viruses in the respiratory tract, and that dual infections are common.  The risk of bacterial respiratory infections is increased by co-infection with viruses and vice-versa, and this has been studied mostly around the relationship between influenza and pneumococcus.” The study also showed that wearing a N95 respirator protected significantly against dual infections.

 “Not only are bacterial pathogens a neglected aspect of occupational health and safety of HCWs, but they interact with viruses to cause increased risk of both viral and bacterial infections. Using a N95 respirator reduces this risk.”

The study adds weight to previous research which has suggested that N95 respirators provide superior respiratory protection to a plain surgical mask for health workers, a finding which continues to be disputed and opposed in the medical community. 

N95 respirators are designed to block at least 95% of airborne particles, but many HCWs find them uncomfortable. Surgical masks are more comfortable, but do not filter particles or fit around the face as well as a respirator.

Most countries have policies that recommend the use of surgical masks only or recommend KN95s only for high-risk procedures, such as those which induce coughing in patients. The US Centers for Disease Control and Prevention recommends that HCWs wear a surgical mask when within 3 feet of a person who has symptoms of a respiratory infection.

“For too long the debate about N95 respirators has focused on theoretical arguments about modes of transmission of respiratory pathogens, because surgical masks are thought to be enough for pathogens spread by large droplets, such as through coughing and sneezing.” Said MacIntyre. “In a practical sense, it doesn’t matter what the mode of transmission is, or how the N95 provides protection, “ said MacIntyre. “If it provides protection, it makes no sense to ignore the evidence and argue about modes of transmission. What matters is knowing whether it prevents infection in a real-life setting such as a hospital. We have shown that it does protect more than a surgical mask. The mechanisms of protection of a mask or respirator against respiratory infection may be multi-modal - it may protect against inhalation of droplets and aerosols, but may also act as a barrier to reduce hand to nose or hand to face contact. All modes are probably important, which is why N95s are superior. There is enough evidence now to show a benefit of N95 respirators, and it’s time to put the occupational health and safety of our health workers first and foremost.”

Paper available online here