In October 2009, NIOSH received requests for HHEs from the management of two dental practices in a metropolitan area of Ohio. The dental practices were concerned about transmission of pH1N1 to dental employees. NIOSH investigators visited each dental practice four separate times over a 6-week period beginning in January 2010. During each site visit, we collected air and surface samples for pH1N1 and seasonal influenza virus. Air samples were collected with bioaerosol samplers that separated airborne particles into three size ranges: > / = 4.1 microm

1.0-4.1 microm

and < / = 1.0 microm aerodynamic diameter. Air samples were collected near patients in exam chairs and at a distance of several feet from patients to distinguish between large and small airborne influenza particles. We also collected NP swabs from dental staff, administered a influenza symptom survey to dental staff, and reviewed symptom surveys that the dental practices had asked patients to complete. No pH1N1 or seasonal influenza A virus was detected in the 48 air samples or 52 surface swab samples we obtained at Dental Practice A, a general dentistry practice. No pH1N1 virus was detected in the 48 air samples collected at Dental Practice B, a pediatric dentistry practice. However, we identified a seasonal influenza A strain (H3N2) (< or = 1 microm in size) from air samples collected near patient exam chairs in three exam rooms at Dental Practice B on March 2, 2010. No pH1N1 or seasonal influenza A virus was found in the 54 surface swabs collected in Dental Practice B. All NP samples collected from dental practice staff at both practices were negative for influenza A viruses. During our sampling dates, none of the dental staff who completed the influenza symptom survey at Dental Practice A had ILI in the prior 7 days. Only one dental staff member who completed the survey at Dental Practice B had ILI in the prior 7 days. Of those who completed the survey at Dental Practice A, only two patients or individuals accompanying patients had ILI in the prior 7 days. At Dental Practice B, six patients or individuals accompanying patients had ILI in the prior 7 days. For staff at Dental Office A, 8% reported getting the pH1N1 vaccine and 25% reported getting the seasonal influenza vaccine. Of the staff at Dental Practice B, 18% reported getting both the pH1N1 and seasonal influenza vaccine. Exposure of dental staff at both practices to airborne pH1N1 and seasonal influenza A viruses during the sampling days appears to have been limited. This may be because the community influenza incidence during the time of our evaluation was below typical seasonal influenza levels. The absence of positive surface swab samples for pH1N1 or seasonal influenza may be primarily due to the low number of patients reporting ILI. We recommend that all employees get the seasonal influenza vaccine every year. Employees should self-assess for influenza symptoms and not report to work if ill. Dental practices should monitor and manage employees who are ill and absent. Additionally, dental practices should consider developing mechanisms to screen patients for ILI symptoms prior to their visits or at the time of check-in. Dental practices should advise patients to consider postponing visits and procedures that are not urgent until 24 hours after the patient is free of fever, especially in times of high influenza activity within the community.