The authors have declared that no competing interests exist.
Conceived and designed the experiments: NJA DKB ZJF JTS. Analyzed the data: NJA ZJF. Wrote the paper: NJA DKB JTS.
Between September 2009 and August 2010, the Centers for Disease Control (CDC) included questions on ILI symptoms on the Behavioral Risk Factor Surveillance System (BRFSS). Washington State collects the occupation of all employed BRFSS respondents. ILI prevalence and prevalence ratios (PR) were calculated by occupational group.
There were 8,758 adult, currently employed, non-military respondents to the Washington BRFSS during the study period. The ILI prevalence for all employed respondents was 6.8% (95% Confidence Interval (95% CI) = 6.1, 7.6). PRs indicated a lower prevalence of ILI in Technicians (PR = 0.4, 95% CI = 0.2, 0.9) and Truck Drivers (PR = 0.2, 95% CI = 0.1, 0.7) and higher prevalence in Janitors and Cleaners (PR = 2.5, 95% CI = 1.3, 4.7) and Secretaries (PR = 2.4, 95% CI = 1.1, 5.4).
Some occupations appear to have higher prevalence of ILI than others. These occupational differences may be explained, in part, by differing levels of social contact with the public or contact with contaminated surfaces at work, or by other occupational factors such as stress or access to health care resources.
Seasonal influenza is costly and associated with missed work and decreased work productivity. Annual United States medical costs for seasonal influenza are estimated to be $10.4 billion
Pandemic influenza also has potentially profound effects on the workforce. Compared to seasonal influenza, pandemic influenza results in greater morbidity and mortality in working age populations
Given the substantial burden of influenza on the workforce, accurate data about its prevalence and highest prevalence occupations are needed to guide prevention efforts. Flu virus transmission usually requires the close proximity of an infected person to a healthy person or via fomites. Therefore, healthcare and other occupations involving frequent contact with infected individuals may be at increased risk for influenza
The BRFSS is an annual, CDC-funded, state-based, random digit-dialed, landline telephone survey of the non-institutionalized adult (≥18 years old) U.S. civilian population. BRFSS collects data on health-related behaviors and health conditions. In addition to the CDC Core questions, states may also select additional CDC modules or develop their own questions to include on their state’s BRFSS. BRFSS core questions collect data on age, gender, race/ethnicity, smoking status, weight, height, and current employment status.
Influenza vaccination status was determined by affirmative response to the question “A flu shot is an influenza vaccine injected into your arm. During the past 12 months, have you had a flu shot?” Or “During the past 12 months, have you had a flu vaccine that was sprayed in your nose? The flu vaccine sprayed in the nose is also called FluMist”.
The 2009 and 2010 Washington State BRFSS cooperation rate was 70.1% and 48.2% respectively, and the response rate was 68.9% and 47.5% respectively
From September 1, 2009 through August 30, 2010, CDC sponsored a BRFSS module on influenza-like illness (ILI). ILI cases were determined by affirmative responses to two questions: “During the past month, were you ill with a fever?”, and “Did you also have a cough and/or sore throat?” Additional ILI questions were included in the BRFSS module, but the number of affirmative responses and/or number of eligible respondents were too small for meaningful interpretation in Washington State
BRFSS respondents are asked if they are currently employed, self-employed, out of work for more than one year, out of work for less than a year, a homemaker, a student or retired. For respondents who are self-employed or currently employed, Washington State BRFSS collects the respondent’s occupation by including the following question: “What is your job title?” If no job title was given, the respondent was then asked “What kind of work do you do?”.
Occupation was collected as narrative text responses and recorded verbatim. Responses were autocoded using the Standardized Occupation and Industry Coding (SOIC) software
To identify occupations with higher prevalence of ILI, prevalence ratios (PRs) were calculated for all 29 individual occupations with more than 70 respondents compared to a reference group. The reference group was an aggregation of all other employed respondents in occupations with less than 71 respondents. The selection of the individual occupations was blinded to ILI status.
The reference group was significantly different (p<0.001) from the aggregate 29 occupations (see
Demographics | ILI | ||||||||||||||||||
% | % ILI, 95% CI | ||||||||||||||||||
Age | Gender | Race | Age | Gender | Months | Vaccinated | |||||||||||||
n | % ILI (95% CI) | ILI Prevalence Ratio (95% CI) | 18–49 | 50–89 | Male | Female | White, Non-Hispanic | Hispanic | All Other Races | Vaccinated | 18–49 | 50–89 | Male | Female | Sept 2009–March 2010 | April 2010–Aug 2010 | Yes | No | |
All Currently Employed | 8,752 | 6.8 (6.1, 7.6) | – | 69.2 | 30.8 | 54.8 | 45.2 | 81.1 | 8.1 | 10.8 | 20.8 | 7.6 (6.6, 8.6) | 5.1 (4.2, 5.9) | 5.8 (4.8, 6.8) | 8.0 (7.0, 9.1) | 7.6 (6.5, 8.6) | 6.0 (4.9, 7.1) | 7.0 (5.1, 8.9) | 7.9 (6.8, 8.9) |
Aggregate of all 29 selected occupations | 4,265 | 6.8 (5.8, 7.8) | 1.0 (0.8, 1.2) | 67.7 | 32.3 | 51.1 | 48.9 | 82.0 | 6.4 | 11.6 | 22.1 | 7.2 (5.8, 8.6) | 6.0 (4.7, 7.2) | 5.2 (3.9, 6.5) | 8.4 (6.8, 10.0) | 8.2 (6.7, 9.7) | 5.1 (3.8, 6.4) | 8.3 (5.3, 11.2) | 7.7 (6.2, 9.2) |
Reference group: All other occupations (with ≤70 respondents) | 4,487 | 6.8 (5.7, 7.9) | 1.0 | 70.7 | 29.3 | 58.8 | 41.2 | 80.2 | 9.7 | 10.1 | 19.6 | 8.0 (6.5, 9.4) | 4.1 (3.1, 5.1) | 6.3 (4.8, 7.8) | 7.6 (6.1, 9.1) | 6.9 (5.6, 8.2) | 6.8 (5.0, 8.5) | 5.8 (3.3, 8.2) | 8.0 (6.4, 9.6) |
Note. CI = confidence interval; all data were weighted to account for BRFSS sampling design.
The number of respondents for the vaccination status question was 6,139.
Using the coded occupational responses and the BRFSS ILI questions, descriptive statistics, ILI prevalence by occupational groups
All analyses were performed using STATA software (STATA Version 8.0, Stata Corporation, College Station, TX, USA 2003). The Washington State BRFSS survey questions and protocols were approved by the Washington State Institutional Review Board.
During the study period, there were 8,752 Washington BRFSS respondents who were 18 to 89 years of age, currently employed for wages or self-employed in non-military occupations. Demographics and vaccination information by occupation are presented in
% | |||||||||
Age | Gender | Race | |||||||
1990 Census Occupation | n | 18–49 | 50–89 | Male | Female | White, Non-Hispanic | Hispanic | All Other Races | Vaccinated |
All Currently Employed | 8,752 | 69.2 | 30.8 | 54.8 | 45.2 | 81.1 | 8.1 | 10.8 | 20.8 |
Managers and Administrators, n.e.c. | 651 | 65.4 | 34.6 | 68 | 32 | 88.3 | 2.7 | 9 | 16 |
Elementary School Teachers | 471 | 61.9 | 38.1 | 35.3 | 64.7 | 90 | 5.7 | 4.3 | 19.6 |
Registered Nurses | 268 | 64 | 36 | 7.5 | 92.5 | 86 | 2.6 | 11.4 | 58.9 |
Nursing Aides, Orderlies and Attendants | 245 | 66.6 | 33.4 | 24.3 | 75.7 | 62.6 | 12 | 25.4 | 27.4 |
Supervisors and Proprietors, Sales Occupations | 185 | 73.2 | 26.8 | 60 | 40 | 83.8 | 3.5 | 12.7 | 19.7 |
Administrative Support Occupations | 180 | 73.4 | 26.6 | 28.5 | 71.5 | 86.8 | 2.4 | 10.8 | 25.7 |
Technicians, n.e.c. | 136 | 72 | 28 | 75.2 | 24.8 | 87.8 | 3.2 | 9 | 20.9 |
Sales Workers, Other Commodities | 133 | 70.2 | 29.8 | 57.7 | 42.3 | 86.4 | 5.4 | 8.2 | 20.2 |
Farmers, except Horticultural | 124 | 71.6 | 28.4 | 73.4 | 26.6 | 37 | 59.6 | 3.4 | 7.1 |
Janitors and Cleaners | 123 | 57.8 | 42.2 | 63 | 37 | 62.6 | 25.8 | 11.6 | 19.1 |
Management Related Occupations, n.e.c | 118 | 69.8 | 30.2 | 34.4 | 65.6 | 81.1 | 2 | 16.9 | 20.7 |
Truck Drivers | 110 | 73.2 | 26.8 | 94.2 | 5.8 | 88.7 | 8.5 | 2.8 | 16.4 |
Managers, Medicine and Health | 105 | 47.1 | 52.9 | 37.9 | 62.1 | 88.1 | 3.9 | 8 | 35 |
Engineers, n.e.c | 97 | 64.3 | 35.7 | 89.2 | 10.8 | 81.7 | 2.8 | 15.5 | 14.9 |
Administrators, Education and Related Fields | 96 | 61.5 | 38.5 | 52.4 | 47.6 | 84.5 | 1.6 | 13.9 | 16.2 |
Secretaries | 95 | 54.7 | 45.3 | 2.6 | 97.4 | 88.4 | 5.7 | 5.9 | 37 |
Bookkeepers, Accounting, and Auditing Clerks | 95 | 55.7 | 44.3 | 6.1 | 93.9 | 86.8 | 2.4 | 10.8 | 21.1 |
Accountants and Auditors | 94 | 68.6 | 31.4 | 37.5 | 62.5 | 91.6 | 0 | 8.4 | 25.1 |
Financial Managers | 93 | 58.1 | 41.9 | 51.3 | 48.7 | 92.4 | 1.4 | 6.2 | 15.9 |
Teachers, n.e.c | 92 | 67.4 | 32.6 | 36.1 | 63.9 | 96.5 | 1.3 | 2.2 | 5.4 |
Investigators and Adjusters, except Insurance | 91 | 73.6 | 26.4 | 28.7 | 71.3 | 76.7 | 7.3 | 16 | 37.1 |
Postsecondary School Teachers | 89 | 58.8 | 41.2 | 62.3 | 37.7 | 78.4 | 1.8 | 19.8 | 20.6 |
Management Analysts | 88 | 56.2 | 43.8 | 67.3 | 32.7 | 74.3 | 5.9 | 19.8 | 12.2 |
Cashiers | 88 | 86.6 | 13.4 | 22.7 | 77.3 | 72.3 | 10.7 | 17 | 19.5 |
Computer Systems Analysts and Scientists | 83 | 82.9 | 17.1 | 82.2 | 17.8 | 54.3 | 7.7 | 38 | 23.9 |
Secondary School Teachers | 83 | 66.4 | 33.6 | 44.7 | 55.3 | 83 | 5.9 | 11.1 | 27.7 |
Construction Laborers | 80 | 69.2 | 30.8 | 91.1 | 8.9 | 74.5 | 21.3 | 4.2 | 19.4 |
General Office Clerks | 80 | 66.7 | 33.3 | 21.1 | 78.9 | 84.8 | 2.7 | 12.5 | 34.9 |
Computer Programmers | 72 | 90.4 | 9.6 | 89.8 | 10.2 | 85.8 | 1.2 | 13 | 11.5 |
Reference group: All other occupations(with ≤70 respondents) | 4,487 | 70.7 | 29.3 | 58.8 | 41.2 | 80.2 | 9.7 | 10.1 | 19.6 |
Note. n.e.c. = not elsewhere classified; all data were weighted to account for BRFSS sampling design.
The n for the vaccination status question was 6,139.
The ILI prevalence for all employed respondents was 6.8% (95% CI = 6.1, 7.6) (
ILI (%) | ||||||||||
Age | Gender | Months | Vaccinated |
|||||||
1990 Census Occupation | % ILI (95% CI) | ILI PR (95% CI) | 18–49 | 50–89 | Male | Female | Sept 2009–March 2010 | April 2010–Aug 2010 | Yes | No |
All Currently Employed | 6.8 (6.1, 7.6) | – | 7.6 | 5.1 | 5.8 | 8.0 | 7.6 | 6.0 | 7.0 | 7.9 |
Managers and Administrators, n.e.c. | 6.5 (4.2, 8.8) | 0.9 (0.6, 1.4) | 7.2 | 5.1 | 5.9 | 7.6 | 8.1 | 4.9 | 7.9 | 7.4 |
Teachers, Elementary School | 5.1 (2.8, 7.3) | 0.7 (0.5, 1.2) | 4.8 | 5.6 | 4.7 | 5.2 | 7.0 | 2.8 | 1.0 | 7.5 |
Registered Nurses | 5.7 (1.6, 9.9) | 0.8 (0.4, 1.8) | 7.7 | 2.3 | – | 6.1 | 7.9 | 3.4 | 9.2 | 4.7 |
Nursing Aides, Orderlies and Attendants | 10.1 (4.9, 15.4) | 1.5 (0.9, 2.6) | 11.1 | 8.1 | – | 8.5 | 12.0 | 8.2 | – | 9.9 |
Supervisors and Proprietors, Sales Occupations | 5.9 (2.3, 9.5) | 0.9 (0.5, 1.6) | 6.6 | 4.0 | 4.4 | 8.2 | 8.3 | 3.2 | – | 5.3 |
Administrative Support Occupations | 9.5 (2.7, 16.3) | 1.4 (0.7, 2.9) | 10.8 | 6.0 | – | 7.4 | 12.4 | 6.2 | – | 10.8 |
Technicians, n.e.c. | 3.0 (0.6, 5.3) |
|
2.4 | 4.4 | 1.5 | – | 4.3 | 1.4 | – | 4.7 |
Sales Workers, Other Commodities | 4.0 (0.0, 8.0) | 0.6 (0.2, 1.7) | 4.1 | 3.5 | 1.2 | 7.6 | 5.3 | 2.2 | – | 5.3 |
Farmers, except Horticultural | 4.0 (0.0, 9.2) | 0.6 (0.2, 2.2) | – | 1.2 | 5.4 | – | 2.1 | – | – | 2.1 |
Janitors and Cleaners | 17.1 (6.5, 27.7) |
|
– | 13.3 | 14.1 | 21.4 | 17.5 | 16.4 | – | 17.9 |
Management Related Occupations, n.e.c | 6.1 (0.8, 11.5) | 0.9 (0.4, 2.2) | 7.0 | 4.1 | – | 8.6 | 10.9 | 2.0 | – | 1.0 |
Truck Drivers | 1.6 (0.0, 3.4) |
|
1.5 | 1.8 | 1.7 | – | 1.0 | – | – | 2.9 |
Managers, Medicine and Health | 7.9 (2.4, 13.4) | 1.1 (0.6, 2.3) | – | 8.6 | – | 10.5 | 8.9 | – | – | – |
Engineers, n.e.c | 7.4 (0.0, 14.9) | 1.1 (0.4, 3.0) | – | – | 8.1 | – | 10.4 | – | – | 11.0 |
Administrators, Education and Related Fields | 4.2 (0.3, 8.2) | 0.6 (0.2, 1.6) | – | 7.5 | 5.5 | – | 2.4 | – | – | 4.1 |
Secretaries | 16.6 (3.7, 29.5) |
|
– | 8.5 | – | 16.5 | – | – | – | – |
Bookkeepers, Accounting, and Auditing Clerks | 9.4 (2.0, 16.8) | 1.4 (0.6, 3.1) | – | 6.7 | – | 9.8 | 12.6 | – | – | 13.1 |
Accountants and Auditors | 5.4 (0.0, 11.6) | 0.8 (0.2, 2.5) | – | – | – | 8.3 | 5.3 | – | – | 14.9 |
Financial Managers | 13.0 (3.1, 23.0) | 1.9 (0.9, 4.2) | – | – | – | 13.8 | 13.2 | – | – | 9.8 |
Teachers, n.e.c | 4.2 (0.0, 8.7) | 0.6 (0.2, 1.8) | – | – | – | 6.6 | 3.4 | – | – | 6.3 |
Investigators and Adjusters, except Insurance | 10.4 (2.5, 18.3) | 1.5 (0.7, 3.3) | – | – | – | 11.6 | – | – | – | 11.9 |
Postsecondary Teachers | 6.2 (0.2, 12.2) | 0.9 (0.3, 2.4) | – | 7.1 | – | – | 6.4 | – | – | – |
Management Analysts | 4.5 (0.0, 10.6) | 0.7 (0.2, 2.6) | – | 2.3 | – | – | – | – | – | 3.1 |
Cashiers | 12.0 (2.2, 21.7) | 1.8 (0.8, 4.0) | 10.5 | – | – | 14.3 | – | – | – | – |
Computer Systems Analysts and Scientists | 6.3 (0.0, 12.8) | 0.9 (0.3, 2.6) | 5.9 | – | 6.9 | – | – | – | – | – |
Secondary School Teachers | 7.7 (0.0, 15.7) | 1.1 (0.4, 3.2) | – | – | – | 11.7 | – | – | – | – |
Construction Laborers | 2.4 (0.0, 5.3) | 0.3 (0.1, 1.2) | – | – | 2.7 | – | – | – | – | 2.7 |
General Office Clerks | 6.5 (0.6, 12.4) | 0.9 (0.4, 2.4) | 15.4 | – | – | 8.2 | – | – | – | – |
Computer Programmers | 4.7 (0.0, 10.5) | 0.7 (0.2, 2.4) | 3.9 | – | 4.4 | – | – | – | – | 5.9 |
Reference group: All other occupations (with ≤70 respondents) | 6.8 (5.7, 7.9) | 1.0 | 8.0 | 4.1 | 6.3 | 7.6 | 6.9 | 6.8 | 5.8 | 8.0 |
Note. CI = confidence interval; n.e.c. = not elsewhere classified; all data were weighted to account for BRFSS sampling design; results for categories with <50 respondents are not reported.
The number of respondents for the vaccination status question was 6,139.
The ILI prevalence for employed 18–49 year old’s was significantly higher than ILI prevalence in employed respondents aged 50–89 years, 7.6% vs. 5.1% (p<0.001) (
Respondents who identified themselves as non-Hispanic Whites had an ILI prevalence of 6.5%; respondents identifying as Hispanics had 8.1% ILI prevalence; and workers identifying as All Other Races had an ILI prevalence of 9.0% (
The highest prevalence of ILI was in female Janitors and Cleaners at 21.4% (
The lowest weighted prevalence of ILI was found in Truck Drivers (1.6%) regardless of age or sex (
Of the 6,139 respondents answering the influenza vaccination questions, 20.8% reported having received an influenza vaccination either by injection or nasal spray (
PR (95% CI) | ||||||||||||
Gender | Age | Vaccinated |
Months | Children in Household | ||||||||
Census 1990 Occupation | n | All | Males | Females | 18–49 years | 50–89 years | Vaccinated |
Unvaccinated | Sept 2009–March 2010 | April 2010–Aug 2010 | Yes | No |
All occupations with >70 respondents | 4,265 | 1.0 (0.8, 1.2) | 0.8 (0.6, 1.2) | 1.1 (0.8, 1.5) | 0.9 (0.7, 1.2) |
|
1.4 (0.8, 2.5) | 1.0 (0.7, 1.3) | 1.2 (0.9, 1.6) | 0.8 (0.5, 1.1) | 0.9 (0.7, 1.3) | 1.1 (0.8, 1.6) |
Registered Nurses | 268 | 0.8 (0.4, 1.8) | – | 0.8 (0.4, 1.7) | 1.0 (0.4, 2.2) | 0.6 (0.2, 1.6) | 1.6 (0.6, 4.1) | 0.6 (0.1, 2.9) | 1.1 (0.5, 2.7) | 0.5 (0.1, 2.2) | 1.0 (0.4, 2.3) | 0.5 (0.2, 1.9) |
Nursing Aides, Orderlies and Attendants | 245 | 1.5 (0.9, 2.6) | 2.4 (0.9, 6.9) | 1.1 (0.6, 2.0) | 1.4 (0.7, 2.7) | 2.0 (0.8, 4.8) | 0.8 (0.2, 3.3) | 1.2 (0.6, 2.5) | 1.7 (0.9, 3.2) | 1.2 (0.4, 3.3) | 0.8 (0.4, 1.7) |
|
Elementary School Teachers | 471 | 0.7 (0.5, 1.2) | – | 0.7 (0.4, 1.2) | 0.6 (0.3, 1.2) | 1.3 (0.7, 2.5) | 0.2 (0.0, 1.2) | 0.9 (0.5, 1.6) | 1.0 (0.6, 1.8) | 0.4 (0.2, 1.0) | 0.6 (0.3, 1.2) | 1.0 (0.5, 1.9) |
Secondary School Teachers | 83 | 1.1 (0.4, 3.2) | 0.4 (0.1, 3.0) | 1.5 (0.5, 4.9) | 1.4 (0.5, 4.1) |
|
3.4 (0.6, 18.6) | 0.7 (0.2, 2.8) | 1.3 (0.4, 3.8) | 0.9 (0.2, 6.5) | 1.5 (0.5, 4.3) |
|
Technicians, n.e.c. | 136 |
|
|
1.0 (0.4, 2.8) | 0.3 (0.1, 1.0) | 1.1 (0.4, 2.8) | 0.5 (0.1, 3.8) | 0.6 (0.2, 1.6) | 0.6 (0.2, 1.6) |
|
|
0.8 (0.3, 2.0) |
Cashiers | 88 | 1.8 (0.8, 4.0) | 0.7 (0.1, 5.0) | 1.9 (0.8, 4.5) | 1.3 (0.5, 3.7) |
|
|
1.9 (0.5, 6.3) | 2.5 (0.9, 6.7) | 0.9 (0.3, 2.8) | 1.7 (0.5, 5.8) | 1.8 (0.7, 4.7) |
Secretaries | 95 |
|
4.3 (0.6, 33.1) | 2.2 (1.0, 4.9) |
|
2.1 (0.8, 5.5) |
|
|
2.3 (0.9, 5.7) | 2.5 (0.8, 7.7) | 2.8 (0.9, 8.5) | 2.4 (0.8, 6.9) |
Janitors and Cleaners | 123 |
|
2.3 (0.9, 5.4) |
|
|
|
– |
|
|
2.4 (0.9, 6.4) | 2.1 (0.9, 5.0) |
|
Truck Drivers | 110 |
|
|
– |
|
0.4 (0.1, 2.1) | – | 0.4 (0.1, 1.1) |
|
0.4 (0.1, 1.6) |
|
0.4 (0.1, 1.5) |
Note. CI = confidence interval; PR = prevalence ratio; n.e.c. = not elsewhere classified; bold font indicates significance at p<0.05; all data were weighted to account for BRFSS sampling design; reference group for the ‘all occupations’ column, and for each row, is composed of those in that category in all occupations with ≤70 respondents.
The original n for the vaccination status question was 6,139.
Analysis of the overall PRs shows significantly lower prevalence of ILI in both Technicians, n.e.c., PR = 0.4 (95% CI = 0.2, 0.9) and Truck Drivers, PR = 0.2 (95% CI = 0.1, 0.7); and significantly higher prevalence in Janitors and Cleaners, PR = 2.5 (95% CI = 1.3, 4.7) and Secretaries, PR = 2.4 (95% CI = 1.1, 5.4) when compared to reference group of occupations (
Registered Nurses did not have an increased risk of ILI compared with the reference group. Nursing Aides, Orderlies and Attendants showed consistently higher prevalence of ILI than Registered Nurses, and higher ILI prevalence than overall ILI prevalence and that of the reference group (
Analysis of the Washington BRFSS ILI data shows that the prevalence of ILI varies by occupation. Significantly higher prevalence of ILI was found in Janitors and Cleaners, and Secretaries; while there was a lower prevalence of ILI in Technicians, n.e.c., and Truck Drivers. To our knowledge, Janitors and Cleaners and Secretaries are occupations that have not previously been identified as having higher ILI prevalence. Other occupations that have been previously considered as having the potential for higher prevalence of ILI, such as Registered Nurses and Teachers (both Elementary and Secondary School), were not found to have any higher prevalence when compared to the reference group. In general, the distribution of ILI by age and gender in Washington BRFSS employed respondents was similar to US patterns for patients hospitalized with H1N1, in which the majority of patients were under 50 years of age
Previous research suggests a higher percentage of ILI in women (9.0%) compared to men (7.1%) and our data confirmed this observation
The results do reflect a higher prevalence of ILI in women and healthcare workers are nearly 80% women
The vaccination rate of the Washington employed population in our data was 20.7% (
Health care occupations (such as Registered Nurses and Nursing Aides, Orderlies, and Attendants) and teaching occupations have potentially high levels of contact with groups such as ill persons or children who may have a higher prevalence of ILI. HCW in particular are often targeted for prevention; and school closures have been identified as a way of social distancing to prevent the transmission of pandemic influenza
In social contact modelling schools are considered a major source of influenza transmission
Socially isolative professions such as Farming, and Truck Driving had a lower prevalence of ILI than other occupations. Though we cannot estimate what kind of exposure Technicians, n.e.c. have to higher ILI prevalence populations, it could be that because they are involved in working with tools, machines, or other such technical work, that they have less close social contact with other persons at work or work more independently.
The occupations with the highest prevalence of ILI were Secretaries, and Janitors and Cleaners. Secretaries may have higher social contact with an infected person in a work setting. Shared office space has been shown to increase the risk for common colds
Differences in PPE use, education, and training in infection control practices may partly explain the increased prevalence of ILI in Janitors and Cleaners. There may also be underlying demographic, socioeconomic, and employment-related factors contributing to differences in ILI prevalence
Psychological stress can alter susceptibility to infections
A study of sickness absence and work factors found sickness absence distributed on an occupational class gradient, with (male) manual workers and clerks having higher relative ratios of abscences for respiratory illnesses (4.21, 3.61 respectively) than engineers (1.14) and managers (reference group, 1.0), and the pattern was similar in women
A lack of access to paid leave may also negatively affect workers in certain occupations. An evaluation of the impact of workplace policies fond that the absence of policies such as paid sick leave contributed a population-attributable risk of 5 million additional cases of ILI, and in particular, 1.2 million of those among Hispanics (also found in the same study to have higher percieved job insecurity)
Of WA BRFSS respondents, female janitors and cleaners had the highest prevalence of ILI (21.4%,
Compared with other occupations, certain health care professionals (Registered Nurses, and Nursing Aides, Assistants and Orderlies) did not have a higher prevalence of ILI. These results are consistent with a previous study
Other studies have shown an increased prevalence of seasonal influenza for all health care workers (HCW)
Given the differences in ILI prevalence by race and gender seen in our small sample, future work should further explore the potential reasons for these differences. Occupational segregation by race or gender might partially explain the higher prevalence of ILI in non-white and Hispanic populations, although our sample was too small to test this. Future work could also benefit from some measure of the contact rates in social and occupational networks; O*NET
While there are some differences in the distribution of the population between the reference group (those occupations with ≤70 respondents) and the distribution of all of the employed, there was no difference in ILI PR overall between the reference group and our aggregate 29 presented occupations (
Multivariate modeling by occupation would be preferable but would have required a larger surveyed population than what we had available. However, the observed results seem biologically plausible in terms of higher or lower exposure (direct social contact or via fomites) resulting in higher or lower risk of ILI by occupation when vaccination rates are considered.
Some possible bias towards the null may have been introduced by assignment of nonspecific narrative responses to larger occupational groups, such as those occupations not elsewhere -classified (n.e.c.).
Another important limitation is that the ILI questions measure non-specific symptoms attributable to many other illnesses like the common cold. Teachers and other school workers have been found to have a higher prevalence of head and chest colds during the school year than all other workers
Since characterizing the degree of social contact necessary to complete work is difficult, OSHA guidance to prepare workplaces for an influenza pandemic recommends limiting “close contact (within 6 feet)” whenever possible, even for occupations at lower and medium exposure risk
We are not aware of any other published study analyzing self-reported ILI prevalence by occupation. This analysis provides valuable insight into the occurrence of ILI in a working population. Additionally, our data are representative of employees in Washington State, with the weighted estimates of the employed Washington population in BRFSS being consistent with estimates of the Washington employed population from other data sources
BRFSS is a national-scale validated survey system that has been used for many years to collect health and behavioral information and set policy. The use of occupational data in this manner is a unique approach to differentiate ILI prevalence within an employed population, and could extend to assisting in pandemic flu planning. If industry and occupation data are collected in more states, or nationally, more occupations could be analyzed and the results would have improved power and the ability to explore differences by race and gender. Even at this limited level, however, one can differentiate ILI prevalence by occupation in the employed Washington population, demonstrating that further research using occupation data to characterize ILI is warranted.
Some occupations appear to have higher prevalence of ILI than others. Some of these differences may be explained, at least in part, by differing levels of social contact and other factors such as stress and access to leave by occupation. Given the serious impact of the flu on the working population, targeting of prevention resources should take occupational exposures into account. Routine collection of industry and occupation information in BRFSS and other surveillance instruments would help in identifying industries and occupations with higher prevalence of ILI or other outcomes of interest and tailoring prevention strategies accordingly.
The authors wish to gratefully acknowledge the study conception contributions of Marie Haring Sweeney, PhD, MPH and Sara E. Luckhaupt MD, MPH from the Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.