The study was conducted at HC, in the city of São Paulo, São Paulo state, Brazil. São Paulo is among the largest cities in Latin America, with 11 million inhabitants. HC, a tertiary care teaching hospital complex affiliated with the University of São Paulo, is a government hospital predominantly for patients covered by the publicly funded Brazilian National Health Service. During the outbreak of pandemic (H1N1) 2009 in Brazil, HC was assigned by the State of São Paulo Health Department as a state reference hospital for persons with severe pandemic (H1N1) 2009.

HC has ≈2,000 beds distributed in 7 institutes. The Central Institute (main building) has 894 beds, including 100 intensive care unit (ICU) beds. The other centers are the Heart Institute (444 beds); Orthopedics Institute (152 beds); Children’s Institute (174 beds); Psychiatry and Neurosurgery Institute (90 beds); Cancer Institute (213 beds); and Radiology Institute, without inpatients, which serves all other institutes. Although also part of the HC complex, the administration building, 2 long-term care facilities (234 beds total), and 1 outpatient rehabilitation center were not included in this study.

As recommended by international guidelines, triage for suspected influenza cases was put in place at all of HC´s institutes. Triage occurred in the existing emergency departments in the Central, Heart, and Children’s Institutes. Persons with confirmed influenza were then referred to designated units within HC for hospitalization. Included in the Central Institute were an ICU (7 beds), an influenza-specific ward (11 beds for semi-intensive care), and a specific ward for pregnant influenza patients (15 beds). In the Children’s Institute, an ICU (2 beds) , a ward (14 beds), and 2 rooms at the emergency department were assigned. Later into the influenza season (August 2009), 2 additional influenza-specific wards were designated in the Heart Institute, with 16 rooms and 32 beds. Although persons with influenza should have been hospitalized preferentially in the above-designated units, a few patients in whom influenza was only suspected after admission and who could not be transferred were hospitalized in nondesignated units.

Laboratory testing for confirmatory diagnosis was conducted for all hospitalized persons suspected to have influenza. Rapid diagnostic tests for influenza were not performed during the pandemic. Before July 2, 2009, samples were collected and sent to the Adolfo Lutz Reference Laboratory, where real-time PCR (rt-PCR) testing was conducted. By July 2, 2009, HC Central Hospital Laboratory started the influenza A (H1N1) rt-PCR. Although available for patients admitted to the hospital, laboratory confirmation of pandemic (H1N1) 2009 infection was not available for HCWs. Thus, suspected cases among HCWs were triaged according to the attending physician’s evaluation. The rt-PCR for suspected influenza in HCWs was made available only on August 24, 2009. The PCR protocol in place was developed by the US Centers for Disease Control and Prevention (10).

During the entire pandemic period, active surveillance for nosocomial pandemic (H1N1) 2009 was performed by the infection control teams. A suspected influenza case was defined, according to national guidelines (11), as fever and respiratory symptoms such as cough or sore throat in the absence of other diagnoses, and confirmed cases were defined as those with positive test results for pandemic (H1N1) 2009.

Following global and national guidelines (8,12), infection control policies for prevention and control of nosocomial transmission of influenza were in place in the hospital. These included contact and droplet precautions taken by HCWs during the care of patients with suspected and confirmed influenza and use of N95 masks only during aerosol-generating procedures.

HC has a centralized occupational health service for workers of all institutes. We assessed ILI in and ILI-associated sick leave for HCWs who are overseen by the hospital’s occupational health service, i.e., physicians; nurses and nurse assistants; and pharmacy, nutrition, laboratory, and administration workers. Cleaning and security services are furnished by third-party service providers; therefore, their staff are not overseen by HC’s occupational health service.

Starting on July 16, 2009, in HC institutes except the Heart Institute, an HCW with suspected influenza received an initial 2-day leave and was reassessed every 2 days until asymptomatic, when he or she returned to work (2-day leave + reassessment policy). In the Heart Institute, a different sick leave policy was adopted in which an HCW with suspected pandemic (H1N1) 2009 infection received a 7-day leave (7-day leave policy). During the prepandemic period, sick leave for respiratory infection was determined on a case-by-case basis after evaluation by a physician (Figure).

We retrospectively evaluated the effect of ILI on HCW absenteeism during the pandemic (H1N1) 2009 outbreak. The main outcome of interest was HCW absenteeism.

We estimated the economic effects of HCW-associated illness from the hospital´s perspective. Costs were estimated retrospectively. Among the various techniques for measuring costs, 1 of the most commonly used is the accounting approach (the conventional costing method). This approach can be divided into 2 categories: the first uses detailed, bottom-up, step-down analyses of accounting to distribute shared costs across the activities considered (also called ingredients approach). The second uses a top-down approach, which makes less detailed estimates of high-level average costs on the basis of aggregate expenditure records. In this study, we used the bottom-up approach as we considered individual ingredients to estimate costs. We compared the effectiveness and cost of the 2 sick leave policies: initial 2-day + reassessment policy and 7-day.

The study was conducted during the first wave of pandemic (H1N1) 2009 in the Southern Hemisphere winter season (May–October 2009). The prepandemic period was defined as August 2008–April 2009. HCW was defined as a professional on the hospital’s payroll, even if the worker did not work directly with patients. This definition excluded students and residents/fellows, as well as workers of third-party service providers (cleaning and security).

We calculated the monthly number, average duration, and rate of influenza sick leaves issued in HC by institute and HCW profession. We determined the proportion of sick leaves taken for ILI in relation to the total number of sick leaves during the pandemic (H1N1) 2009 outbreak (May–October). Rate of influenza-associated sick leaves issued during the pandemic (H1N1) 2009 outbreak (August–October 2009) were compared with the prepandemic period (August–October 2008).

To assess the effectiveness of the 2 sick leave policies, we evaluated the number of nosocomial pandemic (H1N1) 2009 cases. We calculated the total number of sick leaves issued, their average duration, and total days of ILI-associated sick leave for HCWs working under the 7-day and 2-day + reassessment policies during the pandemic period. In addition, monthly rates of ILI-associated sick leave days per 100 HCWs were compared for the 2 sick leave policies by using χ².

The cost analysis considered only ILI and absenteeism in physicians, nurses, and nurse assistants because of the availability of information. Direct medical costs of diagnosis, treatment, and follow-up for HCWs with suspected and confirmed pandemic (H1N1) 2009 were estimated. Direct medical costs also included the cost of replacement HCWs during sick leave. Direct nonmedical costs assessed were transportation of symptomatic HCWs to and from HC for assessment. Indirect costs comprised productivity losses of HCWs during sick leave. Costs for outpatient treatment of HCWs suspected to have influenza comprised medical assessment by the occupational health clinic, specimen collection and rt-PCR (only after August 24, 2009) for laboratory diagnosis, and treatment.

We assumed that 100% of HCWs with suspected influenza received antiviral medication (oseltamivir) according to the official hospital guideline. Twenty percent received antimicrobial drugs (amoxicillin) for secondary bacterial infection, and 70% received symptomatic medication.

HCW hospitalization costs associated with pandemic (H1N1) 2009 were estimated by considering the average daily cost of hospitalization in HC. No information about complications or secondary bacterial infection in hospitalized HCWs with influenza was available for the cost analysis.

When evaluating cost of staff replacement, we assumed that 70% of nurses and nurse assistants and 50% of physicians on sick leave were replaced. We also assumed that HCWs under the 2-day + reassessment policy would return on average 1.5 times for reassessment, thus incurring medical consultations and transportation costs for 1.5 return visits to HC. Under the 7-day policy, we assumed that 10% of HCWs would return for medical consultations during leave; thus, only 10% of HCWs required transportation for reassessment.

We estimated productivity losses by considering the daily 12-hour average salaries for each HCW category based on an average of 5 years of work in HC. Wages and mandatory Social Security and health care contributions were considered. Monthly salary was Brazilian real (R$) 3,071.54 for nurses working 30 h/week; R$2,541.55 for physicians working 20 h/week; and R$1,571.80 for nurse assistants working 30 h/week. One US dollar was equivalent to ≈R$1.80.

We also recalculated the costs for each sick leave policy on the basis of a lowest cost scenario and a highest cost scenario. For the lowest cost scenario, we assumed that HCWs on leave would have returned on average 0.5 times for reevaluation if under the 2-day + reassessment policy and would not have returned for the 7-day policy. We also assumed that 5% of HCWs received antimicrobial drugs and 20% received treatment for symptoms. Staff replacement was assumed to have been 30% for nurses and nurse assistants and 10% for physicians. For the highest cost scenario, we assumed that each HCW had 3 return consultations for the 2-day + reassessment policy and 1.5 return visits for the 7-day policy, that 60% of HCWs received antimicrobial drugs, and that 100% received treatment for symptoms. Staff replacement in the highest cost scenario was assumed to be 100% for nurses and nurse assistants and 80% for physicians.

The inputs, values, and data sources are presented in Table 1. HC maintains a centralized occupational health database in which sick leave of HCWs since August 2008 is registered by International Statistical Classification of Diseases and Related Health Problems (13). The number of HCWs placed on sick leave during August 2008–October 2009 because of diseases of the respiratory system reported as codes J10 (Influenza due to other identified influenza virus) and J11 (Influenza, virus not identified), by using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, was evaluated (13). Cost data were obtained from the hospital administration.