ABSTRACT
OBJECTIVES: Hospital-based surveillance of influenza and acute respiratory infections relies on International Classification of Diseases (ICD) codes and hospital laboratory reports (Standard-of-Care). It is unclear how many cases are missed with either method, i.e. remain undiagnosed/coded as influenza and other respiratory virus infections. Various influenza-like illness (ILI) definitions co-exist with little guidance on how to use them. We compared the diagnostic accuracy of standard surveillance methods with a prospective quality management (QM) programme at a Berlin children's hospital with the Robert Koch Institute. METHODS: Independent from routine care, all patients fulfilling pre-defined ILI-criteria (QM-ILI) participated in the QM programme. A separate QM team conducted standardized clinical assessments and collected nasopharyngeal specimens for blinded real-time quantitative PCR for influenza A/B viruses, respiratory syncytial virus, adenovirus, rhinovirus and human metapneumovirus. RESULTS: Among 6073 individuals with ILI qualifying for the QM programme, only 8.7% (528/6073) would have undergone virus diagnostics during Standard-of-Care. Surveillance based on ICD codes would have missed 61% (359/587) of influenza diagnoses. Of baseline ICD codes, 53.2% (2811/5282) were non-specific, most commonly J06 ('acute upper respiratory infection'). Comparison of stakeholder case definitions revealed that QM-ILI and the WHO ILI case definition showed the highest overall sensitivities (84%-97% and 45%-68%, respectively) and the CDC ILI definition had the highest sensitivity for influenza infections (36%, 95% CI 31.4-40.8 for influenza A and 48%, 95% CI 40.5-54.7 for influenza B). CONCLUSIONS: Disease-burden estimates and surveillance should account for the underreporting of cases in routine care. Future studies should explore the effect of ILI screening and surveillance in various age groups and settings. Diagnostic algorithms should be based on the WHO ILI case definition combined with targeted testing.
Subject(s)
Quality Assurance, Health Care/statistics & numerical data , Respiratory Tract Infections/diagnosis , Standard of Care/statistics & numerical data , Virus Diseases/diagnosis , Viruses/isolation & purification , Adolescent , Child , Child, Preschool , Female , Hospitals , Humans , Infant , Infant, Newborn , Influenza, Human/classification , Influenza, Human/diagnosis , International Classification of Diseases/standards , Male , Nasopharynx/virology , Population Surveillance , Prospective Studies , Quality Assurance, Health Care/standards , Real-Time Polymerase Chain Reaction , Respiratory Tract Infections/classification , Respiratory Tract Infections/virology , Standard of Care/standards , Virus Diseases/classificationABSTRACT
The evolution of influenza viruses is increasingly pursued by molecular analyses that complement classical methods. The analyses focus on the two surface proteins hemagglutinin (HA) and neuraminidase (NA) which determine the viral antigenic profile. Influenza A(H3N2) viruses are exceptionally variable, so that usually at least two virus variants cocirculate at the same time. Together with influenza B viruses they caused approximately 90% of influenza virus infections in Germany during the last 12 seasons, while influenza A(H1N1) viruses only played a subordinate part. Unexpectedly, reassorted viruses of subtype A(H1N2) appeared during the seasons 2001/02 and 2002/03, but were isolated only rarely and gained no epidemiological significance. Furthermore, during the season 2001/02 influenza B viruses of the Victoria-lineage reappeared in Germany and other countries of the northern hemisphere after 10 years of absence. These viruses reassorted with the cocirculating Yamagata-like influenza B viruses, as could be seen by the appearance of viruses with a Victoria-like HA and a Yamagata-like NA.
