Mask-wearing and respiratory infection in healthcare workers in Beijing, China

ORIGINAL ARTICLE

Mask-wearing and respiratory infection in healthcare workers in Beijing, China

Peng Yang^I; Holly Seale^II; C Raina MacIntyre^III; Haiyan Zhang^IV; Zhen Zhang^V; Yi Zhang^VI; Xiaoli Wang^VI; Xinyu Li^VII; Xinghuo Pang^VIII; Quanyi Wang^VIII

^IMD; Lecturer, Beijing Center for Disease Prevention and Control (CDC), Beijing, China; Capital Medical University School of Public Health and Family Medicine, Beijing, China

^IIMD; Lecturer, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia

^IIIProfessor, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia

^IVMD; Lecturer, Dong Cheng District CDC, Beijing, China

^VMD; Lecturer, Xi Cheng District CDC, Beijing, China

^VIMD; Associate Lecturer, Beijing CDC, Beijing, China; Capital Medical University School of Public Health and Family Medicine, Beijing, China

^VIIMD; Lecturer, Beijing CDC, Beijing, China; Capital Medical University School of Public Health and Family Medicine, Beijing, China

^VIIIMD; Professor, Beijing CDC, Beijing, China; Capital Medical University School of Public Health and Family Medicine, Beijing, China

^{Correspondence to}

ABSTRACT

OBJECTIVES: The aim of the study was to determine rates of mask-wearing, of respiratory infection and the factors associated with mask-wearing and of respiratory infection in healthcare workers (HCWs) in Beijing during the winter of 2007/2008.

METHODS: We conducted a survey of 400 HCWs working in eight hospitals in Beijing by face to face interview using a standardized questionnaire.

RESULTS: We found that 280/400 (70.0%) of HCWs were compliant with mask-wearing while in contact with patients. Respiratory infection occurred in 238/400 (59.5%) subjects from November, 2007 through February, 2008. Respiratory infection was higher among females (odds ratio [OR], 2.00 [95% confidence interval {CI}, 1.16-3.49]) and staff working in larger hospitals (OR, 1.72 [95% CI, 1.092.72]), but was lower among subjects with seasonal influenza vaccination (OR, 0.46 [95% CI, 0.280.76]), wearing medical masks (reference: cotton-yarn; OR, 0.60 [95% CI, 0.39-0.91]) or with good mask-wearing adherence (OR, 0.60 [95% CI, 0.37-0.98]). The risk of respiratory infection of HCWs working in low risk areas was similar to that of HCWs in high risk area.

CONCLUSION: Our data suggest that female HCWs and staffs working in larger hospitals are the focus of prevention and control of respiratory infection in Beijing hospitals. Mask-wearing and seasonal influenza vaccination are protective for respiratory infection in HCWs; the protective efficacy of medical masks is better than that of cotton yarn ones; respiratory infection of HCWs working in low risk areas should also be given attention.

Keywords: masks; respiratory tract infections; health personnel.

INTRODUCTION

Influenza pandemic has been a global public health issue in recent years,¹ and in 2009, a pandemic of a novel H1N1 influenza virus of swine origin occurred.^2,3 During the initial stages of an influenza pandemic, supplies of vaccines and antiviral medications are likely to be delayed or inadequate to treat a very large number of affected individuals. Therefore, non-pharmacological interventions will be important, including the use of respirators and/or medical masks, which is able to confer respiratory protection.^4-6 If hospitals are to continue to function adequately during a pandemic, reliable access to effective protection strategies for healthcare workers (HCWs) will be imperative. Reducing transmission to HCWs may not only help support the healthcare workforce, but may also prevent influenza transmission to patients.⁷

It is commonly acknowledged that adherence with an intervention can change with perception of risk during a pandemic or an outbreak of unknown origin. Since the epidemic of SARS in Beijing in 2003, awareness and commitment to infection control increased, including the use of masks among HCWs. However, we are not aware of the exact rate of and adherence to mask-wearing after the SARS outbreak in 2003. Furthermore, we commonly assume that frontline HCWs are at increased risk of respiratory infection, but to the best of our knowledge there is no data examining this in our setting. Therefore, the purpose of our study was to determine the level of mask-wearing and respiratory infection in healthcare workers during an influenza season in Beijing, China.

METHODS

Subjects and survey design

Between April 20, 2008 and May 15, 2008, we undertook a survey to examine the level of mask-wearing and respiratory infection in HCWs from eight hospitals, in Beijing, China. If we assumed that the proportion of HCWs with good mask-wearing adherence (wearing the mask for > 70% of patient-contact time) was equal to 50%, a 5% precision, with a 95% confidence interval according to the formula stated by Daniel,⁸ the required sample size for this survey would be 384 HCWs. Eventually, 400 HCWs were enrolled. These 400 HCWs came from a range of different departments and wards representing high and low risk settings for respiratory infection (respiratory, emergency, infectious disease and surgical departments) of eight hospitals in Beijing, using a two-stage random sampling technique. For this study, we classified the first three wards/departments as being high-risk settings for respiratory pathogen transmission and the surgical department as being low risk. In the first stage, eight hospitals were randomly selected from 23 level 2 or 3 hospitals in Beijing. In China, hospitals are categorized into three levels (Level 1, 2 and 3) according to the magnitude (Level 3 > Level 2 > Level 1).⁹ In the second stage, for each selected hospital, 50 subjects were randomly enrolled in this survey from respiratory, emergency, infectious disease and surgical departments.

Data collection

Using a standardized questionnaire, we developed a survey that assessed: demographic characteristics; professional designation and clinical duties; attitude and adherence to mask-wearing, mask types used; hand washing frequency, seasonal influenza vaccination; and respiratory infection (clinical respiratory illness [CRI], defined as having at least two of the following symptoms simultaneously: fever, cough, sore throat, nasal congestion or rhinorrhea)¹⁰ during the 2007/2008 (from November, 2007 through February, 2008) influenza season.

Attitude to mask-wearing was assessed by asking the following question: Do you think it is necessary to wear masks when in contact with patients? Attitude was categorized as active (necessary to wear masks when in contact with patients) and not active (not necessary to wear masks when in contact with patients).

Mask-wearing adherence was measured by the following question: for what percentage of patient-contact time did you wear a mask or respirator? According to expert opinion, adherence was categorized as good (wearing the mask for > 70% of patient-contact time) and poor (wearing the mask for < 70% of patient-contact time).

Hand washing frequency was assessed by asking the following question: Do you think it is necessary to wash hands after contact with each patient? Frequency was categorized as frequent (necessary to wash hands after contact with each patient) and not frequent (not necessary to wash hands after contact with each patient).

Statistical analysis

Questionnaire data were entered in duplicate using EpiData Software, and data were analyzed using SPSS 11.5 statistical package (SPSS Inc., Chicago, Illinois, USA). Univariate and multivariate logistic regression analyses were conducted to determine predictors of mask-wearing adherence and respiratory infection in HCWs. Predictive factors were first analyzed by univariate analysis, and then factors with p-values < 0.5 or those that were thought to be clinically significant by professional view were included in the multivariable model; backward logistic regression was conducted by removing variables with p > 0.1. For all statistical analyses two-tailed tests were used, and statistical significance was defined as p < 0.05.

RESULTS

Subject characteristics

All 400 subjects selected for this survey participated in and completed the study. The median age was 35 years and about 81% (324/400) were female. About 47.8 % (191/400) were doctors, and 52.2% (209/400) were nurses; 52.7% (211/400) were classified as being in a junior role, and 80% (320/400) were working in high-risk settings. About 28.5% (114/400) reported having taken seasonal influenza vaccination. Detailed demographic characteristics of the subjects are reported in Table 1.

Mask use and respiratory infection in subjects in seasonal influenza season

All subjects (100%) reported mask use. The majority (70%, 280/400) of participants self reported good adherence with masks. About 84.0% (336/400) reported adverse effects of mask-wearing, and 43.0% (172/400) reported more than two adverse effects (Table 2). The most commonly reported adverse effect was breathing difficulties (56.5%, 226/400). The washable, reusable cotton-yarn mask was the most common type of mask used as reported by participants (59.8%, 239/400), followed by medical masks (40.2%, 161/400). Close to 60% of participants reported having had clinical respiratory illness (59.5%, 238/400) during the influenza season. (Table 2).

Predictors associated with mask use adherence

Multivariate analysis showed that good mask-wearing adherence was higher among females (odds ratio [OR], 3.34 [95% confidence interval {CI}, 1.77-6.33; p < 0.001), level 3 hospital (reference: level 2; OR, 2.61 [95% CI, 1.52-4.49]; p= 0.001), high risk department (reference: low risk; OR, 2.05 [95% CI, 1.06-3.97]; p = 0.033), intermediate level (reference: senior level; OR, 2.55 [95% CI, 1.10-5.91]; p = 0.029) and junior level (reference: senior level; OR, 2.77 [95% CI, 1.23-6.24]; p = 0.014), active attitude to mask-wearing (OR, 12.25 [95% CI, 6.13-24.50]; p < 0.001) and frequent hand-washing (OR, 2.06 [95% CI, 1.20-3.54]; p = 0.009) (Table 3).

Predictors associated with respiratory infection

Multivariate analysis showed that females (OR, 2.0 [95% CI, 1.16-3.49]; p = 0.013) and staff working in level 3 hospitals (reference: level 2; OR, 1.72 [95% CI, 1.09-2.72]; p = 0.02) were at increased risk of respiratory infection. But subjects with seasonal influenza vaccination (OR, 0.46 [95% CI, 0.28-0.76]; p = 0.002), wearing medical masks (reference: cotton-yarn; OR, 0.60 [95% CI, 0.39-0.91]; p = 0.018) or with good mask-wearing adherence (reference: poor; OR, 0.60 [95% CI, 0.37-0.98]; p = 0.041) were at lower risk. The risk of respiratory infection of HCWs working in low risk areas was similar to that of HCWs in high risk areas (Table 4). Although frequent hand-washing was a protective predictor for respiratory infection (OR, 0.65 [95% CI, 0.43-0.97]; p = 0.034) in univariate analysis, this action was not associated with respiratory infection in multivariate analysis.

DISCUSSION

In our study, we found high self-reported mask adherence, despite the majority of HCWs having reported adverse effects of mask-wearing. This high level of mask-wearing adherence may be attributed to enhanced management of nosocomial infection control and improved consciousness among HCWs following the SARS outbreak in Beijing in 2003, especially after the occurrence of SARS infection in HCWs.¹¹ We found that the majority of our participants used re-usable cotton-yarn masks, followed by medical masks. N95 masks were not reported as being used routinely. It may be hypothesized that the cost of N95 masks may be a potential barrier for their use in these wards, and departments prefer to re-usable cotton-yarn masks which could be considered as more economically viable in the setting of limited funding/resources.

In this study, female and junior/intermediate HCWs had better adherence to mask-wearing than their counterparts, which may be due to better consciousness of self-protection of females and junior/intermediate HCWs who are much more prone to comply with the hospital infection control policies. HCWs of level 3 hospitals had higher level of adherence to mask-wearing, compared to their counterparts in level 2 facilities. This may be due to the stricter and more complete regulations of infection control in larger hospitals.

HCWs from high risk departments were found to have higher levels of adherence with mask-wearing, compared to their counterparts from low risk areas. This may be due to increased awareness of risk in these departments. We found that it did not matter if the staff member was working in a high or low risk department, anyone who had a "positive attitude" to mask-wearing also had good adherence with mask-wearing. In our study, participants who reported frequent hand-washing were also found to have good adherence with mask-wearing.

In this study close to 60% of participants self-reported having a respiratory infection during the influenza season. Surprisingly, there was no significant difference between rates reported among participants of high risk areas and those from low risk areas. This finding suggested that healthcare workers working in low risk areas had the same risk of respiratory infection as those in high risk areas in Beijing hospitals.

We are unsure why females had a higher reported rate of infection - a possible explanation could be that female healthcare workers have closer patient contact than their male counterparts. The level 3 hospital represented the higher risk of respiratory infection compared to level 2 facilities suggesting that level 3 hospitals, which have larger population of sick patients, are a priority for measures to protect health care workers.

The coverage of seasonal influenza vaccination is always of concern, especially in HCWs.^12-14 In this survey, we found that 28.5% (114/400) of participants were vaccinated, and seasonal influenza vaccination showed a protective effect, underscoring the importance of seasonal influenza vaccination for HCWs.

This study showed that HCWs with good adherence to mask-wearing were at lower risk of respiratory infection, which indicates the protective effect of masks, also found in previous studies.^4-6,15 The protective efficacy of masks/respirators is provided through a combined effect of transmission blocking potential, the fit and related air leakage of the mask/respirator, and the consistency in the use of masks/respirators. Their efficacy is graded on the level of protection the material offers, assuming a perfect fit and optimal compliance.¹⁶ Medical masks are designed to protect the environment from respiratory droplets produced by the wearer. Research studies on the filtration and fit of medical masks show wide variation in penetration of aerosol particles (4% to 90%) and a higher amount of face seal leakage when compared to respirators.¹⁷ The fit of cloth masks/cottonyarn masks, which are widely used in Asia, is likely to be even looser than medical masks and hence, cloth masks are likely to have a lower level of protection, suggested by the higher efficacy of medical masks found in this study. In addition, reuse of cloth masks may lead to contamination, which adds to the risk of respiratory infection. But there are no clinical data associated with cloth masks currently.

There are a number of limitations in this study. Firstly, information regarding vaccine uptake, frequency of masks/respirators use, frequency of hand washing and cases of respiratory infection were all based on self-report. This study is therefore subject to problems of recall bias, and final results may be overestimated. Another limitation is that we cannot comment on whether HCWs who reported a respiratory infection were infected in or out of the hospital setting.

Despite these limitations, we provide the first quantitative estimate of mask-wearing and respiratory infection among HCWs in Beijing during the influenza season after the SARS outbreak in 2003.

ACKNOWLEDGMENTS

This study was supported by grants from the National High Technology Research and Development Program of China (863 Program) (2008AA02Z416) and Beijing Natural Science Foundation (7082047).

Submitted on: 8/12/2010

Approved on: 9/28/2010

Financial Support: This study was supported by grants from the National High Technology Research and Development Program of China (863 Program) (2008AA02Z416) and Beijing Natural Science Foundation (7082047).

We declare no conflict of interest.

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Publication Dates

• Publication in this collection
  06 Apr 2011
• Date of issue
  Apr 2011

History

• Received
  12 Aug 2010
• Accepted
  28 Sept 2010