Rapid molecular detection of influenza outbreaks in nursing homes.
BACKGROUND
Nursing home influenza outbreaks occur in spite of established vaccination programs, and require rapid and sensitive laboratory confirmation for timely intervention.


OBJECTIVE
To evaluate diagnostic approaches for rapid confirmation of nursing home influenza outbreaks.


METHODS
Influenza virus real-time PCR and Directigen Flu A+B enzyme immunoassay were performed on nasopharyngeal swabs, nasopharyngeal washes and throat swabs collected from residents with clinical suspicion of influenza during seven probable nursing home outbreaks in 2004-2005 and 2005-2006. The efficacy of specimen sampling and transport management by Public Health Service outbreak team was evaluated.


RESULTS
PCR detected influenza RNA in 80% (68/85) of specimens from 81% (38/47) residents, confirming six suspected outbreaks. Immunoassay sensitivity was highest on nasopharyngeal swabs (38%; 11/29) with a positive predictive value of 100% compared to PCR. Nasopharyngeal swabs were equally sensitive to nasopharyngeal washes by PCR. Nasopharyngeal wash sampling appeared unpractical due to common underlying disability of residents. Outbreak team support was associated with a shorter time to PCR diagnosis compared to outbreaks with no logistical support (mean, 28.2h vs. 84h; P=0.05).


CONCLUSIONS
Influenza real-time PCR on nasopharyngeal swabs, obtained by Public Health Service outbreak teams, enabled rapid and sensitive confirmation of nursing home influenza outbreaks.
Gooskens
J
J
Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. j.gooskens@lumc.nl <j.gooskens@lumc.nl>
Swaan
C M
CM
Claas
E C J
EC
Kroes
A C M
AC
D000368:Aged; D000369:Aged, 80 and over; D000956:Antigens, Viral / Q000032:analysis; D003428:Cross Infection / Q000175:diagnosis / Q000453:epidemiology; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D009735:Nursing Homes; D009975:Orthomyxoviridae / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D010614:Pharynx / Q000821:virology; D011237:Predictive Value of Tests; D012367:RNA, Viral / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity
D000956:Antigens, Viral; D012367:RNA, Viral