NIOSH Activities: Surveillance

Man Sneezing into tissue

Tracking Influenza Cases and Preventive Measures


Public health surveillance is the ongoing process for systematically collecting, analyzing, and interpreting health-related data. These data are needed for planning, implementing, and evaluating public health practice. Surveillance results are shared in a timely manner with those who prevent and control health and safety risks.

The influenza surveillance activities of the National Institute for Occupational Safety and Health (NIOSH) fit into the bigger picture of Centers for Disease Control and Prevention (CDC) influenza surveillance activities. This work monitors disease burden; virus characteristics; vaccine or antivirals availability, use, and adverse events; medical care or infrastructure; school and workforce protection, and other non-pharmaceutical interventions.

CDC divides influenza disease surveillance into five categories, described on the Overview of Influenza Surveillance in the United States:

  • Viral Surveillance
  • Outpatient Illness Surveillance
  • Mortality Surveillance
  • Hospitalization Surveillance
  • Summary of the Geographic Spread of Influenza

NIOSH tracks workplace factors that affect influenza activity by incorporating occupational information into broad influenza surveillance systems developed and maintained by other CDC centers.

NIOSH Influenza-related Surveillance Activities

General Description: More research was needed on the epidemiology by occupational grouping of the 2009 H1N1 influenza. From April through July work status information was available for 1,361 of 4,334 (31.8%) people age 16 or older with laboratory-confirmed 2009 H1N1 influenza from Florida, Kansas, Oregon, and Wisconsin. A North American Industry Classification System (NAICS) 2007 code was assigned to each employed person. For a subset of these people, an occupation code was also assigned.

Relevance to Worker Safety and Health: This analysis identified occupations and industry sectors that may face a higher risk of influenza infection.

Key Findings:

  • Of 898 employed individuals, 32% were healthcare personnel and 68% worked in the non-healthcare sectors.
  • The non-healthcare industry sectors representing the highest proportions of influenza cases were public administration, educational services, and accommodation and food services.
  • Among the affected Wisconsin healthcare workers, 54% were health paraprofessionals, 34% were health professionals, and 13% were other workers.

NIOSH investigators said the analysis highlighted the need to collect data on occupation and industry more consistently in future influenza surveillance.

Status: The project is complete. More information can be found in the published peer-reviewed journal article: Occupational Distribution of Persons With Confirmed 2009 H1N1 Influenza

Point of Contact: CDC-INFO

General Description: The Influenza Hospitalization Network (FluSurv-NET) conducted surveillance for population-based, laboratory-confirmed influenza-related hospitalizations during 2009–2010 . The network covers more than 80 counties in the 10 CDC Emerging Infections Program (EIP) states (CA, CO, CT, GA, MD, MN, NM, NY, OR, and TN) and six additional states (ID, MI, OH, OK, RI and UT).

The NIOSH Division of Surveillance, Hazard Evaluations, and Field Studies (DSHEFS), coordinating with CDC colleagues, collected occupational data on adults hospitalized with influenza in 2009–2010 through the EIP states.

Relevance to Worker Safety and Health: More information is needed about which specific groups of workers are at highest risk of acquiring both pandemic and seasonal influenza. This is one of the first times occupational information has been collected in a traditional CDC influenza surveillance system.

Key Findings: During the 2009–2010 influenza season, the proportion of workers hospitalized for influenza was lower than their proportion in the general population. However, among those workers who were hospitalized with laboratory-confirmed influenza, some industry sectors were overrepresented compared with what would be expected if workers from all industry sectors had the same risk for hospitalization because of influenza. These industry sectors were transportation and warehousing; administrative and support and waste management and remediation services; healthcare; and accommodation and food service.

Status: This project is complete. An article describing the key findings from 2009–2010 is now available.

Point of Contact: CDC-INFO

General Description: The CDC conducted the National 2009 H1N1 Flu Survey (NHFS) from October 2009 through June 2010 to track 2009 H1N1 and seasonal influenza vaccination coverage nationally on a weekly basis. The survey was a random-digit-dialed telephone survey based on a rolling weekly sample of respondents with landline and cellular telephones. Monthly targets were set to achieve about 4,889 completed interviews from landline households and 1,111 from cellular-only or cellular-mostly households, or about 6,000 interviews in all (from

The NIOSH Division of Surveillance, Hazard Evaluations, and Field Studies (DSHEFS) worked with CDC colleagues to add four questions to the NHFS to address occupational issues, including employment status, occupation, industry, and missed work.

Relevance to worker safety and health: The four occupational questions enabled analyses of these factors:

  • Incidence of self-reported respiratory illness among workers by industry and occupation
  • Knowledge, attitudes, and practices of workers regarding 2009 H1N1 influenza
  • Vaccination uptake among workers (seasonal and 2009 H1N1 influenza)
  • Days of work missed due to respiratory illness

Key Findings: In a representative sample of 28,710 employed adults, 5.5% reported influenza-like illness symptoms in the month before the interview, and 23.7% received the 2009 pandemic H1N1 (pH1N1) influenza vaccine. Among employed adults, the highest prevalence of influenza-like illness was reported by those employed in the industry groups “Real estate and rental and leasing” (10.5%) and “Accommodation and food services” (10.2%), and in the occupation groups “Food preparation and serving related” (11.0%) and “Community and social services” (8.3%). Both seasonal influenza and pH1N1 vaccination coverage were relatively low in all of these groups of workers. Adults not in the labor force (homemakers, students, retired persons, and persons unable to work) had influenza-like illness prevalence and pH1N1 vaccination coverage similar to those found in all employed adults combined. In contrast, influenza-like illness prevalence was higher and pH1N1 vaccination coverage was lower among unemployed adults (those looking for work). These results suggest that adults employed in certain industries and occupations have increased risk for influenza infection, and most of these workers did not receive seasonal or pH1N1 influenza vaccine. Unemployed adults might also be considered a high risk group for influenza.

A report has been published in MMWR.

Status: Completed

Point of Contact: CDC-INFO

General description: The Behavioral Risk Factor Surveillance System (BRFSS) is a state-based system of health surveys (reaching 400,000 respondents). It collects information by phone on health risk behaviors, preventive health practices, and healthcare access primarily related to chronic disease and injury. Two special modules were added during the 2009–2010 influenza season to address the 2009 H1N1 influenza pandemic. A module on influenza-like illness ran from September 2009 to March 2010, and a module on vaccination ran from October 2009 to June 2010. Every state except Vermont used them. However, the content for these modules was set before NIOSH was involved, and information on industry and occupation was not systematically collected. Analyses designed specifically to address issues related to worker safety and health were not, therefore, conducted using these data.

Relevance to worker safety and health: As of 2015, 25 states collect information on employed BRFSS respondents’ industry and occupation using an optional, NIOSH-sponsored module that was funded for 2013–2016. NIOSH is also working with colleagues to have industry and occupation questions regularly and systematically tracked in the core annual BRFSS for all states so that, in the future, health outcomes measured in the system (including influenza-like illness) can be analyzed by industry and occupation. CDC uses these data to monitor influenza vaccination coverage by industry and occupation.

Key Findings: O’Halloran AC, Lu PJ, Williams WW, Schumacher P, Sussell A, Birdsey J, Boal WL, Sweeney MH, Luckhaupt SE, Black CL, Santibanez TA [2017]. Influenza vaccination among workers—21 U.S. states, 2013.external icon  Am J Infect Control 45:410-416.

Point of Contact: CDC-INFO

General Description: NIOSH monitors health-related workplace absenteeism—absences specifically due to workers’ own illness, injury, or other medical issue—among full-time workers in the United States. Each month, NIOSH updates an influenza season-based time series chart showing the amount of health-related absenteeism among full-time workers, using Current Population Survey (CPS) data from the previous month. Monthly health-related workplace absenteeism estimates for the current season are compared to an epidemic threshold established using baseline absenteeism data from the previous five seasons, averaged by month. Absenteeism is considered significantly higher than expected in months when the lower limit of the estimate’s margin of error is higher than the epidemic threshold.

Relevance to worker safety and health: Monitoring health-related absenteeism among workers is especially useful for assessing the occurrence of some illnesses, such as influenza. Health-related workplace absenteeism data add to the traditional influenza surveillance conducted by CDC, which is mainly based on disease reporting from doctors and laboratory testing. Monitoring trends in health-related workplace absenteeism across the U.S. can also help:

  • Doctors, other healthcare personnel, employers and workers be more informed about disease occurrence and severity during an influenza pandemic and during seasonal epidemics.
  • Public health authorities better target prevention messages and evaluate how well pandemic control measures work.
  • Emergency responders prepare for future pandemics.

Key Findings: Workplace absenteeism is an important supplementary measure of influenza’s impact on the working population that can inform prevention messaging and pandemic preparedness planning. State and local health authorities, as well as employers, might wish to consult these results when developing and targeting prevention messages and use them to monitor long-term trends for their jurisdiction during interpandemic periods. Analysis of aggregated absenteeism data from multiple seasons might also help identify occupational groups at higher risk for influenza transmission.

Status: Results of surveillance analyses from the current and past seasons are made available online.

A report in MMWR describes the results of surveillance analyses from the high-severity 2017 – 2018 influenza season.

A publication in Disaster Med Public Health Prep 2013, describes the results of a pilot study conducted during the 2009 H1N1 pandemic that provided the basis for NIOSH’s current absenteeism surveillance.

Point of Contact: CDC-INFO

General Description: This group works on the annual internet panel survey of HCP nationwide to estimate influenza vaccination coverage among U.S. HCP each year.

Relevance to worker safety and health: Comprehensive worksite intervention strategies that include vaccination promotion and convenient access to vaccination at no cost might increase vaccination coverage among HCP.

Key Findings: The links below are recent publications from the Advisory Committee on Immunization Practices.

Status: In Process.

Point of Contact: CDC-INFO

General Description: This project identified, described, and evaluated surveillance systems used at the Vanderbilt University Medical Center to track activities, resources, and outcomes related to personal protective equipment (PPE). This work complements other infection control measures being used to control transmission of infectious diseases during an influenza pandemic or other disasters. The project uses existing and new systems at Vanderbilt University Medical Center to collect data by active and passive surveillance methods, and it will share data in a standardized way. The data include key fields regarding training, fitting, utilization, resources, exposures, and outcomes relating to PPEs. The project will help develop recommended best practices for collecting and maintaining such data.

Relevance to worker safety and health: Descriptions of existing systems in use by medical centers across the country, along with Vanderbilt University Medical Center data, were used to demonstrate a standard dataset for export to a national surveillance system. Such a dataset provides information useful to the CDC in an evolving infectious disease situation, allowing the CDC to provide clear and useful PPE guidance to healthcare facilities in real time.

Key Findings: In process.

Status: Completed.

Point of Contact: CDC-INFO

General Description: This project assessed how respiratory protection is used for influenza exposure among healthcare workers in 16 California hospitals during the H1N1 influenza pandemic. Participating in the study were 204 healthcare workers, representing a variety of clinical specialties and roles including unit managers, respiratory protection administrators, and direct care providers. The project also used observational methods to better understand personal protective equipment donning and doffing practices.

Relevance to worker safety and health: Findings from the Respirator Evaluation in Acute Care Hospitals Study serve as a ‘snapshot’ of: (1) the extent to which hospitals in California have implemented required elements of a respiratory protection program for influenza, and (2) the usage of personal respiratory protection for influenza exposure among California healthcare workers.

Key Findings:

  • 50% of the hospital managers reported that their facility had experienced a shortage of respirators between April 2009 and the survey period (January 20 to February 23, 2010).
  • The observational data indicates improper use of respiratory protective equipment as evidenced by donning and doffing practices, specifically:
    • Not performing a seal check
    • Improper strap placement
    • Touching the facepiece upon doffing
  • 65% of healthcare workers felt that they were at a high risk of becoming ill with influenza due to their work, 96% felt that wearing an N95 or better respirator could help protect them from on-the-job exposures to influenza, and 94% said that N95 respirators are more effective at protecting them from influenza than surgical masks.
  • When asked how respondents knew that they needed to wear a respirator, the top two responses suggested that healthcare workers waited to be “cued” by signage on the door or to be told during shift report.

Status: Completed

Key Findings:  Evaluation of Respiratory Protection Programs and Practices in California Hospitals During the 2009–2010 H1N1 Influenza Pandemicexternal icon

Point of Contact: CDC-INFO

General Description: The objective of this project was to extend and build upon the work previously completed under the Respirator Evaluation in Acute Care Hospitals Study Intervention and Evaluation (REACH I) by examining the effectiveness of various interventions for improving respiratory protection programs in California acute care facilities

Relevance to worker safety and health: Findings from REACH I suggest that N95 respirators are being widely used, although gaps in training, appropriate donning, and evaluation have been identified. This project identified and evaluated effective interventions and best practices to strengthen California hospitals’ respiratory protection programs and reinforce healthcare workers’ proper use of respiratory protection.

Key Findings: A toolkit of effective strategies was developed and tested in 14 California hospitals. The California Respirator Program Administrators toolkit can be accessed at: icon

Status: Completed

Point of Contact: CDC-INFO

General Description: REACH II expanded on REACH I to evaluate hospitals’ written respiratory protection programs and assess healthcare workers’ use of respiratory protection for influenza (droplet) and aerosol-transmissible exposures in five regions of the United States (Northeast, Southeast, Midwest, Southwest, and West).

Relevance to worker safety and health: Findings from REACH II serve as a snapshot of (1) the extent to which hospitals across the United States have implemented required elements of a respiratory protection program for influenza, and (2) the usage of personal respiratory protection for seasonal influenza exposure among healthcare workers.

Key Findings:

  • Data collection was completed in five regions and six U.S. states. The final data set included 98 hospitals, more than 1,500 participants (such as healthcare workers, hospital and unit managers), as well as more than 300 demonstrations of respirator donning and doffing.
  • More than 80% of participating hospitals reported they adhered to many of the OSHA-required respiratory protection program elements, such as:
    • Medical evaluations and fit testing before first respirator use
    • Employee training on how and when to use respiratory protection
    • Respiratory protection guidelines regarding close contact with a patient with suspected or confirmed infectious disease or seasonal influenza
  • The lowest levels of adherence concerned factors, such as:
    • Frequency of medical evaluations
    • Informing staff about the model and size of respirator they have been fit tested for
    • Formal evaluations of respiratory protection programs
  • Similarly to REACH I findings, healthcare workers demonstrated improper donning and doffing procedures:
    • 46% used incorrect strap placement
    • 85% did not perform a seal check
    • 57% did not use straps during doffing
    • 45% used improper respirator disposal methods

Hospital and Unit Managers reported overall higher adherence rates to respiratory protection guidelines than healthcare workers. In other words, those closest to the “bedside” (more contact with patients) were less likely to provide correct survey responses about respiratory protection recommendations or requirements for selected diseases.

Status: Completed a paper published in the American Journal of Infection Control, Respiratory Protection Policies and Practices Among the Health Care Workforce Exposed to Influenza in New York State: Evaluating Emergency Preparedness for the Next Pandemic,external icon summarized findings from New York State.

Point of Contact: CDC-INFO

Page last reviewed: March 28, 2018