Showing papers by "Amanda Balish published in 2009"

Antigenic and Genetic Characteristics of Swine-Origin 2009 A(H1N1) Influenza Viruses Circulating in Humans

Abstract: Since its identification in April 2009, an A(H1N1) virus containing a unique combination of gene segments from both North American and Eurasian swine lineages has continued to circulate in humans. The lack of similarity between the 2009 A(H1N1) virus and its nearest relatives indicates that its gene segments have been circulating undetected for an extended period. Its low genetic diversity suggests that the introduction into humans was a single event or multiple events of similar viruses. Molecular markers predictive of adaptation to humans are not currently present in 2009 A(H1N1) viruses, suggesting that previously unrecognized molecular determinants could be responsible for the transmission among humans. Antigenically the viruses are homogeneous and similar to North American swine A(H1N1) viruses but distinct from seasonal human A(H1N1).

Triple-Reassortant Swine Influenza A (H1) in Humans in the United States, 2005–2009

Abstract: Background Triple-reassortant swine influenza A (H1) viruses — containing genes from avian, human, and swine influenza viruses — emerged and became enzootic among pig herds in North America during the late 1990s. Methods We report the clinical features of the first 11 sporadic cases of infection of humans with triple-reassortant swine influenza A (H1) viruses reported to the Centers for Disease Control and Prevention, occurring from December 2005 through February 2009, until just before the current epidemic of swine-origin influenza A (H1N1) among humans. These data were obtained from routine national influenza surveillance reports and from joint case investigations by public and animal health agencies. Results The median age of the 11 patients was 10 years (range, 16 months to 48 years), and 4 had underlying health conditions. Nine of the patients had had exposure to pigs, five through direct contact and four through visits to a location where pigs were present but without contact. In another patient, hu...

Effectiveness of Inactivated Influenza Vaccines Varied Substantially with Antigenic Match from the 2004–2005 Season to the 2006–2007 Season

Abstract: Background We estimated the effectiveness of inactivated influenza vaccines for the prevention of laboratory-confirmed, medically attended influenza during 3 seasons with variable antigenic match between vaccine and patient strains. Methods Patients were enrolled during or after a clinical encounter for acute respiratory illness. Influenza infection was confirmed by culture or reverse-transcriptase polymerase chain reaction. Case-control analyses were performed that used data from patients who were ill without influenza (hereafter, "test-negative control subjects") and data from asymptomatic control subjects from the population (hereafter, "traditional control subjects"). Vaccine effectiveness (VE) was estimated as [100 x (1-adjusted odds ratio)]. Influenza isolates were antigenically characterized. Results Influenza was detected in 167 (20%) of 818 patients in 2004-2005, in 51 (14%) of 356 in 2005-2006, and in 102 (11%) of 932 in 2006-2007. Analyses that used data from test-negative control subjects showed that VE was 10% (95% confidence interval [CI], -36% to 40%) in 2004-2005, 21% (95% CI, -52% to 59%) in 2005-2006, and 52% (95% CI, 22% to 70%) in 2006-2007. Using data from traditional control subjects, VE for those seasons was estimated to be 5% (95% CI, -52% to 40%), 11% (95% CI, -96% to 59%), and 37% (95% CI, -10% to 64%), respectively; confidence intervals included 0. The percentage of viruses that were antigenically matched to vaccine strains was 5% (3 of 62) in 2004-2005, 5% (2 of 42) in 2005-2006, and 91% (85 of 93) in 2006-2007. Conclusions Influenza VE varied substantially across 3 seasons and was highest when antigenic match was optimal. VE estimates that used data from test-negative control subjects were consistently higher than those that used data from traditional control subjects.

Evaluation of rapid influenza diagnostic tests for detection of novel influenza A (H1N1) virus - United States, 2009.

Abstract: The recent appearance and worldwide spread of novel influenza A (H1N1) virus has highlighted the need to evaluate commercially available, widely used, rapid influenza diagnostic tests (RIDTs) for their ability to detect these viral antigens in respiratory clinical specimens. As an initial assessment, CDC conducted an evaluation of multiple RIDTs. Sixty-five clinical respiratory specimens collected during April-May 2009 that had previously tested positive either for novel influenza A (H1N1) or for seasonal influenza A (H1N1) or A (H3N2) viruses by real-time reverse transcription--polymerase chain reaction (rRT-PCR) assay were used in the evaluation. The results showed that, although the RIDTs were capable of detecting novel A (H1N1) virus from respiratory specimens containing high levels of virus (as indicated by low cycle threshold [Ct] values), the overall sensitivity was low (40%-69%) among all specimens tested and declined substantially as virus levels decreased (and Ct values increased). These findings indicate that, although a positive RIDT result can be used in making treatment decisions, a negative result does not rule out infection with novel influenza A (H1N1) virus. Patients with illnesses compatible with novel influenza A (H1N1) virus infection but with negative RIDT results should be treated empirically based on the level of clinical suspicion, underlying medical conditions, severity of illness, and risk for complications. If a more definitive determination of infection with influenza virus is required, testing with rRT-PCR or virus isolation should be performed. Additional evaluations of the accuracy of RIDTs in detecting novel influenza A (H1N1) virus should be conducted.

Development of a new candidate h5n1 avian influenza virus for pre-pandemic vaccine production

Abstract: Background Highly pathogenic H5N1 avian influenza viruses currently circulating in birds have caused hundreds of human infections, and pose a significant pandemic threat. Vaccines are a major component of the public health preparedness for this likely event. The rapid evolution of H5N1 viruses has resulted in the emergence of multiple clades with distinct antigenic characteristics that require clade-specific vaccines. A variant H5N1 virus termed clade 2.3.4 emerged in 2005 and has caused multiple fatal infections. Vaccine candidates that match the antigenic properties of variant viruses are necessary because inactivated influenza vaccines elicit strain-specific protection. Objective To address the need for a suitable seed for manufacturing a clade 2.3.4 vaccine, we developed a new H5N1 pre-pandemic candidate vaccine by reverse genetics and evaluated its safety and replication in vitro and in vivo. Methods A reassortant virus termed, Anhui/PR8, was produced by reverse genetics in compliance with WHO pandemic vaccine development guidelines and contains six genes from A/Puerto Rico/8/34 as well as the neuraminidase and hemagglutinin (HA) genomic segments from the A/Anhui/01/2005 virus. The multi-basic cleavage site of HA was removed to reduce virulence. Results The reassortant Anhui/PR8 grows well in eggs and is avirulent to chicken and ferrets but retains the antigenicity of the parental A/Anhui/01/2005 virus. Conclusion These results indicate that the Anhui/PR8 reassortant lost a major virulent determinant and it is suitable for its use in vaccine manufacturing and as a reference vaccine virus against the H5N1 clade 2.3.4 viruses circulating in eastern China, Vietnam, Thailand, and Laos.