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Purpose: This study aimed to determine incidence rates of novel influenza A (H1N1) infection among healthcare personnel with different exposure risks during the 2009 H1N1 pandemic. Methods: From August 2009 until April 2010, 66 healthcare workers from a 410 bed teaching hospital in Amsterdam were monitored. The following three different exposure groups were created: a high- ( n = 26), intermediate- ( n = 20), and low-risk group ( n = 20). Throat swabs were collected each week and analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in order to detect the H1N1 virus. Blood was drawn at study enrollment and once monthly thereafter, and serum specimens were tested with an H1N1-specific hemagglutination-inhibition serologic assay. Influenza-like signs and symptoms were assessed weekly. Results: One of 26 high-risk group participants proved H1N1 positive once by RT-PCR. This corresponds to an incidence rate in the high-risk group of 5.7/1,000 person weeks (95% CI 0-17/1,000). None of the intermediate- and low-risk group participants proved H1N1 positive by RT-PCR. Significant antibody titer rises in convalescent sera were demonstrated in three participants: one was a confirmation of the case that had proved H1N1 positive by RT-PCR; the others occurred in two asymptomatic participants belonging to the low- and high-risk groups. An influenza-like illness was assumed in four participants from the high- ( n = 1), intermediate- ( n = 1) and low-risk ( n = 2) groups; these findings were not confirmed by positive results from either diagnostic test. Conclusions: This study demonstrates a low incidence rate of influenza A (H1N1) infection among healthcare workers during the 2009 H1N1 pandemic in a setting with high hygiene standards. [ABSTRACT FROM AUTHOR]

Aim: To determine causative respiratory pathogens and describe epidemiological and clinical characteristics in a paediatric population with influenza-like illness during the 2009 H1N1-pandemic. Methods: Observational study of 412 children visiting an outpatient clinic of a Dutch teaching hospital. Results: From August to December 2009, 412 children were tested at the clinic; 32% proved H1N1-positive, confirmed by reverse-transcriptase-polymerase-chain-reaction (RT-PCR). Pathogens were detected in 65% of samples. Influenza A(H1N1) (n = 132), human rhinovirus (n = 55), respiratory syncytial virus (n = 45) and adenovirus (n = 34) were mostly identified. Co-infections were seen in 34 children (8.3%). Mean age was 6.8 and 4.2 years in H1N1-positive and H1N1-negative cases, respectively (p < 0.01). H1N1-positive outpatient children reported fever, cough and rhinorrhoea more frequently than their H1N1-negative counterparts. Of 72 hospitalized children, 31% proved H1N1-positive; all showed a relatively mild clinical illness. None of the children had been admitted to an intensive care unit or died. Oseltamivir treatment was initiated in 72 children and discontinued in 42 (63%) when RT-PCR results turned negative. Conclusion: The 2009 H1N1-pandemic showed a mild clinical course in a Dutch paediatric outpatient clinic population. Respiratory pathogens were detected in the majority of children with influenza-like illness and influenza A(H1N1) virus was identified in one-third. Testing symptomatic children during an influenza pandemic has effectively limited the use of oseltamivir. [ABSTRACT FROM AUTHOR]