Surveillance for outbreaks of influenza-like illness in the institutionalized elderly

Respiratory outbreaks are common in aged-care facilities (ACFs), are both underreported and frequently identified late, and are often associated with considerable burden of illness and death. There is emerging evidence that active surveillance coupled with early and systematic intervention can reduce this burden. Active surveillance for influenza-like illness and rapid diagnosis of influenza were established in 16 ACFs in Sydney, Australia, prior to the winter of 2006. A point-of-care influenza test and laboratory direct immunofluorescence tests for common respiratory viruses were used for diagnosis. We achieved early identification of seven respiratory disease outbreaks, two of which were caused by influenza. For the influenza outbreaks, antiviral treatment and prophylaxis were initiated 4–6 days from symptom onset in the primary case. A simple active surveillance system for influenza was successfully implemented and resulted in early detection of influenza and other respiratory disease outbreaks. This enabled earlier implementation of prevention and control measures and increased the potential effectiveness of anti-influenza chemoprophylaxis.

Evaluation of twenty rapid antigen tests for the detection of human influenza A H5N1, H3N2, H1N1, and B viruses

Twenty rapid antigen assays were compared for their ability to detect influenza using dilutions of virus culture supernatants from human isolates of influenza A H5N1 (clade 1 and 2 strains), H3N2 and H1N1 viruses, and influenza B. There was variation amongst the rapid antigen assays in their ability to detect different influenza viruses. Six of the 12 assays labeled as distinguishing between influenza A and B had comparable analytical sensitivities for detecting both influenza A H5N1 strains, although their ability to detect influenza A H3N2 and H1N1 strains varied. The two assays claiming H5 specificity did not detect either influenza A H5N1 strains, and the two avian influenza-specific assays detected influenza A H5N1, but missed some influenza A H3N2 virus supernatants. Clinical trials of rapid antigen tests for influenza A H5N1 are limited. For use in a pandemic where novel influenza strains are circulating (such as the current novel influenza A H1N1 09 virus), rapid antigen tests should ideally have comparable sensitivity and specificity for the new strains as for co-circulating seasonal influenza strains.

Enhancement of influenza surveillance with aggregate rapid influenza test results: New Mexico, 2003-2007

OBJECTIVES

We sought to determine whether monitoring rapid influenza laboratory tests improved the influenza-like illness surveillance already in place in New Mexico.

METHODS

For the past 3 influenza seasons, the New Mexico Department of Health examined influenza-like illness visits and positive rapid influenza test results.

RESULTS

The proportion of positive rapid influenza test results started to rise earlier than did the percentage of clinical visits because of influenza-like illness in each of the past 3 influenza seasons: 5 weeks earlier during the 2004-2005 season; 3 weeks earlier in 2005-2006; and 2 weeks earlier in 2006-2007. In addition, rapid influenza tests showed a spike in influenza B activity late in the 2005-2006 season that influenza-like illness syndrome surveillance did not.

CONCLUSIONS

Laboratory-based rapid influenza test surveillance required relatively few resources to implement and offered a sensitive mechanism to detect the onset of influenza activity while allowing for the distinction of influenza types.

The use of oseltamivir during an influenza B outbreak in a chronic care hospital

BACKGROUND

Residents of nursing homes and long-term care facilities are at a higher risk of outbreaks of influenza and of serious complications of influenza than those in the community. In late July 2005, a 90-bed chronic care psycho-geriatric hospital in Sydney, Australia, reported cases of influenza-like illness (ILI) occurring amongst its residents.

METHODS

An investigation to confirm the outbreak, and its cause, was undertaken. Influenza vaccination levels amongst residents, and the effects of antiviral drugs used for prevention and treatment, were assessed. Oseltamivir was only given to the residents, in the form of both treatment and prophylaxis.

RESULTS

A total of 22 out of 89 residents met the clinical case definition of ILI with onset on or after 27 July 2005. This represents an attack rate of 25%. Oseltamivir was commenced on day 9 of the outbreak. Influenza B was identified in six residents as the causative agent of the outbreak. No deaths or acute hospitalization were recorded for this outbreak and there were no further reported cases after the introduction of oseltamivir. Vaccine effectiveness was 75% and the strain of influenza B isolated was well matched to that year's vaccine.

CONCLUSIONS

There are few data on the use of oseltamivir in influenza B outbreaks. Early antiviral intervention appeared to curtail this outbreak of influenza B in a chronic care facility. We found high vaccine effectiveness in this frail, institutionalized population, highlighting the importance of influenza vaccination for residents of chronic care facilities.

Near-patient assays for diagnosis of influenza virus infection in adult patients

Rapid and reliable diagnosis of influenza is essential for identification of contagious patients and effective patient management. Near‐patient assays allow establishment of the diagnosis within minutes in young children, and this study aimed to evaluate near‐patient assays in relation to the patient’s age. A total of 194 patients with laboratory‐confirmed influenza A/H3N2 virus infection, diagnosed within a prospective cohort study, were included. Cryopreserved nasopharyngeal swabs collected from these patients were tested by four near‐patient assays (Binax Now Influenza A&B, Quick S‐Influ A/B, Influ‐A&B Respi‐Strip, and Actim Influenza A&B). The main outcome measure was sensitivity of the near‐patient assays in relation to the age of patients. The Binax Now, Quick S‐Influ, Influ‐A&B Respi‐Strip and Actim assays had overall sensitivities of 19%, 18%, 26%, and 40%, respectively. The estimated sensitivity for influenza A/H3N2 virus detection in nasopharyngeal swabs was 17–56% in children 1 year of age and decreased to 8–22% in patients 80 years of age (logistic regression). The sensitivity of the Influ‐A&B Respi‐Strip and Actim assays decreased significantly with increasing age (p 0.014 and p 0.033, respectively (logistic regression)), a trend for decrease was observed for the Binax Now assay (p 0.074 (logistic regression)), and the low sensitivity of the Quick S‐Influ assay was similar in children and adults. Less than one‐fourth of diagnosed influenza A/H3N2 virus infections can be identified in elderly patients using a near‐patient assay. Consequently, near‐patient assays are of limited value for confirming the diagnosis when influenza is clinically suspected in adults. Antiviral therapy and additional diagnostic procedures cannot be withheld on the basis of a negative near‐patient assay result, particularly in adult patients.

Programme of the Community Network of Reference Laboratories for Human Influenza to improve Influenza Surveillance in Europe

All laboratories participating in the Community Network of Reference Laboratories for Human Influenza in Europe (CNRL) co-ordinated by the European Influenza Surveillance Scheme (EISS) should be able to perform a range of influenza diagnostics. This includes direct detection, culture, typing, subtyping and strain characterisation of influenza viruses, diagnostic serology and the creation of archives for clinical specimens and virus isolates. To improve the capacity and quality of the laboratories of the CNRL and to increase the consistency in performance among all 25 European Union countries plus Norway, Romania, and Switzerland, five task groups were set up in February 2005. These task groups developed work programmes in the areas of virus isolation, antibodies, molecular virology, quality control assessment and antiviral susceptibility testing. This report outlines the programmes and the results achieved in the first half-year of operation of the task groups. The action plans are challenging and it is expected that these efforts will lead to considerable improvements in the performance of the laboratories and in the standardisation of methods employed in Europe with regard to routine influenza surveillance and early warning for emerging viruses.

Influenza outbreak control in confined settings

Early reporting, on-site laboratory testing, and rapid mass vaccination may limit influenza outbreaks in confined settings.

Influenza may rapidly disseminate within populations living in confined settings, causing considerable morbidity and disrupting daily activities. We describe an influenza A outbreak on a military base where 3,000 young adults, most of whom were unvaccinated, lived in close daily contact. Visits to the base clinic by 48 persons with acute respiratory illness within 2 days allowed early identification of this outbreak and prompted immediate epidemiologic investigation. Overall, 85 personnel (2.83% of base population) met the case definition for influenzalike illness. On-site laboratory confirmation with field detection kits, rapid implementation of respiratory illness control protocols, and a mass vaccination campaign were applied to limit disease dissemination. The outbreak was halted 14 days after the mass vaccination campaign was completed. We review the control measures available for controlling influenza outbreaks in confined settings and discuss the role of rapid mass vaccination within this context.