Dear Sir,

Thank you for your letter in response to our recent publication, “Debate on MERS-CoV respiratory precautions: surgical mask or N95 respirators?”(1) Based on the pore sizes of the protective apparatus and the size of the virus, we agree that there is probably no difference between surgical masks and N95 respirators.(2) Both of these respiratory protective devices will continue to remain in use by different institutions, but we may never be able to directly compare the efficacy of the surgical mask and N95 respirator head to head in randomised controlled trials, especially when dealing with a novel emerging pathogen with a high mortality rate. It is more important that both surgical masks and N95 respirators are worn properly, as suggested by Noti et al,(3) to prevent the inhalation of respiratory pathogens.

Our understanding of the transmission of MERS-CoV is still evolving. More research is required and our infection control policies and recommendations must continue to evolve as new data emerges.

Yours sincerely,
Jasmine Shimin Chung1, Moi Lin Ling2, Wing Hong Seto3, Brenda Sze Peng Ang4, Paul Anantharajah Tambyah5
1Department of Infectious Diseases, 2Infection Control Unit, Singapore General Hospital, Singapore, 3University of Hong Kong, School of Public Health, Hong Kong, 4Communicable Disease Centre, Tan Tock Seng Hospital, 5Division of Infectious Diseases, National University Health System, Singapore.


1. Chung SJ, Ling ML, Seto WH, Ang BS, Tambyah PA. Debate on MERS-CoV respiratory precautions: surgical mask or N95 respirators? Singapore Med J 2014; 55:294-7.
2. Wiwanitkit V. N-95 face mask for prevention of bird flu virus: an appraisal of nanostructure and implication for infectious control. Lung 2006; 184:373-4.
3. Noti JD, Lindsley WG, Blachere FM, et al. Detection of infectious influenza virus in cough aerosols generated in a simulated patient examination room. Clin Infect Dis 2012; 54:1569-77.