Todd F. Hatchette

Two successive outbreaks of mumps in Nova Scotia among vaccinated adolescents and young adults

Background: Before the widespread use of vaccine, mumps was the most common cause of viral meningitis (up to 10% of mumps infections). Vaccination programs have resulted in a drop of more than 99% in the number of reported mumps cases in the United States and Canada. Although rare in Canada, outbreaks have recently occurred throughout the world, including a large outbreak in the United Kingdom, where more than 56 000 cases were reported in 2004–2005. Methods: Two recent outbreaks in Nova Scotia were investigated by public health officials. Cases were defined by laboratory confirmation of infection (i.e., isolation of mumps virus by culture) or clinical diagnosis in people epidemiologically linked to a laboratory-confirmed case. The people infected were interviewed to determine possible links and to identify contacts. Mumps virus was cultured from urine and throat specimens, identified via reverse-transcriptase polymerase chain reaction (RT-PCR) and subjected to phylogenetic analysis to identify the origin of the strain. Results: The first outbreak involved 13 high-school students (median age 14 yr): 9 who had previously received 2 doses of measles–mumps–rubella vaccine (MMR) and 4 who received a single dose. The second outbreak comprised 19 cases of mumps among students and some staff at a local university (median age 23 yr), of whom 18 had received only 1 dose of MMR (the other received a second dose). The viruses identified in the outbreaks were phylogenetically similar and belonged to a genotype commonly reported in the UK. The virus from the second outbreak is identical to the strain currently circulating in the UK and United States. Interpretation: The predominance in these outbreaks of infected people of university age not only highlights an environment with potential for increased transmission but also raises questions about the efficacy of the MMR vaccine. The people affected may represent a “lost cohort” who do not have immunity from natural mumps infection and were not offered a 2-dose schedule. Given the current level of mumps activity around the world, clinicians should remain vigilant for symptoms of mumps.

Influenza A virus inhibits cytoplasmic stress granule formation

An important component of the mammalian stress response is the reprogramming of translation. A variety of stresses trigger abrupt polysome disassembly and the accumulation of stalled translation preinitiation complexes. These complexes nucleate cytoplasmic stress granules (SGs), sites of mRNA triage in which mRNAs from disassembling polysomes are sorted and the fates of individual transcripts are determined. Here, we demonstrate that influenza A virus (IAV) actively suppresses SG formation during infection, thereby allowing translation of viral mRNAs. Complete inhibition of SG formation is dependent on the function of the viral nonstructural protein 1 (NS1); at late times postinfection, cells infected with NS1‐mutant viruses formed SGs in a double‐stranded RNA‐activated protein kinase (PKR)‐dependent fashion. In these cells, SG formation correlated with inhibited viral protein synthesis. Together, these experiments demonstrate the antiviral potential of SGs and reveal a viral countermeasure that limits SG formation.—Khaperskyy, D. A., Hatchette, T. F., McCormick, C. Influenza A virus inhibits cytoplasmic stress granule formation. FASEB J. 26, 1629‐1639 (2012). www.fasebj.org

Influenza A Virus Host Shutoff Disables Antiviral Stress-Induced Translation Arrest

Influenza A virus (IAV) polymerase complexes function in the nucleus of infected cells, generating mRNAs that bear 5′ caps and poly(A) tails, and which are exported to the cytoplasm and translated by host machinery. Host antiviral defences include mechanisms that detect the stress of virus infection and arrest cap-dependent mRNA translation, which normally results in the formation of cytoplasmic aggregates of translationally stalled mRNA-protein complexes known as stress granules (SGs). It remains unclear how IAV ensures preferential translation of viral gene products while evading stress-induced translation arrest. Here, we demonstrate that at early stages of infection both viral and host mRNAs are sensitive to drug-induced translation arrest and SG formation. By contrast, at later stages of infection, IAV becomes partially resistant to stress-induced translation arrest, thereby maintaining ongoing translation of viral gene products. To this end, the virus deploys multiple proteins that block stress-induced SG formation: 1) non-structural protein 1 (NS1) inactivates the antiviral double-stranded RNA (dsRNA)-activated kinase PKR, thereby preventing eIF2α phosphorylation and SG formation; 2) nucleoprotein (NP) inhibits SG formation without affecting eIF2α phosphorylation; 3) host-shutoff protein polymerase-acidic protein-X (PA-X) strongly inhibits SG formation concomitant with dramatic depletion of cytoplasmic poly(A) RNA and nuclear accumulation of poly(A)-binding protein. Recombinant viruses with disrupted PA-X host shutoff function fail to effectively inhibit stress-induced SG formation. The existence of three distinct mechanisms of IAV-mediated SG blockade reveals the magnitude of the threat of stress-induced translation arrest during viral replication.

Investigation of the first cases of human-to-human infection with the new swine-origin influenza A (H1N1) virus in Canada

The outbreak of human infection due to the novel swine-origin influenza A (H1N1) virus began in Mexico in March 2009. As of July 6, 2009, more than 94 000 laboratory-confirmed cases were reported in over 100 countries, including 7983 cases in Canada. In this report, we describe the epidemiologic and clinical characteristics of the first cluster of reported cases of human-to-human transmission of the new influenza virus in Canada.

Switching Gears for an Influenza Pandemic: Validation of a Duplex Reverse Transcriptase PCR Assay for Simultaneous Detection and Confirmatory Identification of Pandemic (H1N1) 2009 Influenza Virus

ABSTRACT Rapid methods for the detection and confirmatory identification of pandemic influenza A virus (also known as pandemic [H1N1] 2009) are of utmost importance. In this study, a conventional reverse transcriptase PCR (RT-PCR) assay for the detection of influenza A virus and the hemagglutinin of swine lineage H1 (swH1) was designed, optimized, and validated. Nucleic acids were extracted from 198 consecutive nasopharyngeal, nasal, or throat swab specimens collected early in the outbreak (127 negative specimens, 66 specimens with pandemic [H1N1] 2009 influenza virus, 3 specimens with seasonal [H1N1] influenza A virus, and 2 specimens with seasonal [H3N2] influenza A virus). The performance characteristics of the duplex RT-PCR assay were assessed and compared to those of various detection methods: a monoplex RT-PCR assay at the National Microbiology Laboratory, a real-time RT-PCR assay using a Centers for Disease Control and Prevention protocol, an in-house multiplex RT-PCR assay (targeting influenza A virus, influenza B virus, and respiratory syncytial virus), and a rapid antigen test (the Binax Now Influenza A & B assay). The sensitivity of the duplex RT-PCR assay for influenza A virus detection was 97.2%, whereas the sensitivities were 74.6%, 71.8%, 47.8%, and 12.7% for the other four assays, respectively. The duplex RT-PCR assay was also able to identify swH1 in 94% of the cases, thereby reducing the number of specimens forwarded to reference laboratories for confirmatory identification. Only a limited number of specimens that contained influenza A virus had amounts of virus that fell below the limit of detection of the assay with the swH1 primers. Overall, the duplex RT-PCR assay is a reliable method for the simultaneous detection and confirmatory identification of pandemic (H1N1) 2009 influenza virus and would be particularly attractive to laboratories without real-time RT-PCR capabilities.

Natural History of Q Fever in Goats

During the spring of 1999, an outbreak of Q fever resulted in 30 abortions among 174 (17%) goats in a caprine cooperative in Newfoundland. The intent of this study was to determine the natural history of Coxiella burnetii infection in goats. Twenty-four goats on one farm were followed through the next two kidding seasons following the Q fever outbreak. Antibodies to phases I and II C. burnetii were determined using an indirect immunofluorescence assay and samples of placentas were cultured for C. burnetii and polymerase chain reaction was used to identify C. burnetii DNA. Phase I antibody was present in high levels and was maintained over the study period, while phase II antibody levels declined to the seronegative range in 60% of the infected goats. Molecular studies suggest that excretion of C. burnetii in the placenta of infected goats seems to be limited to the next kidding season following an outbreak. We therefore conclude that C. burnetii infection in goats seems to be limited to two kidding seasons. Phase I antibody levels are maintained, while phase II antibody levels decline.

Multiplex PCR tests sentinel the appearance of pandemic influenza viruses including H1N1 swine influenza.

Abstract Background Since the turn of the century seven new respiratory viruses have infected man and two of these have resulted in worldwide epidemics. Both SARS Coronavirus which quickly spread to 29 countries in February 2003 and H1N1 swine influenza that recently spread from Mexico to 30 countries in three weeks represent major pandemic threats for mankind. Diagnostic assays are required to detect novel influenza strains with pandemic potential. Objective In this report we evaluate the ability of a multiplex PCR test (xTAG™ RVP) to detect new, “non-seasonal” influenza viruses including the H1N1 swine influenza A/swine/California/04/2009. Study design Laboratory based study using retrospective and prospective specimens. Results This multiplex PCR test detected the present of non-seasonal (non-H1, non-H3) influenza in 20 of 20 patients infected with H1N1 swine flu virus. In addition to detecting the current swine flu the xTAG™ RVP test detected the H5N1 A/Vietnam/1203/2004 high pathogenicity avian influenza virus that circulated in South East Asia in 2003 as well as 17 out of 17 influenza A viruses representing 11 HA subtypes isolated from birds, swine and horses not yet seen in the human population. Conclusion Based on these results we believe that this molecular test can perform an important role as a sentinel test to detect novel non-seasonal influenza A viruses in patients presenting with influenza-like illness (ILI) and therefore act as an early warning system for the detection of future pandemic influenza threats.

Interim estimates of 2014/15 influenza vaccine effectiveness in preventing laboratory-confirmed influenza-related hospitalisation from the Serious Outcomes Surveillance Network of the Canadian Immunization Research Network, January 2015.

The 2014/15 influenza season in Canada has been characterised to date by early and intense activity dominated by influenza A(H3N2). A total of 99.0% (593/599) hospitalisations for laboratory-confirmed influenza with a known influenza virus type enrolled in sentinel hospitals of the Serious Outcomes Surveillance Network of the Canadian Immunization Research Network were due to influenza A. Of the 216 with a known subtype, influenza A(H3N2) accounted for 99.1% (n=214). Interim unmatched vaccine effectiveness (VE) estimates adjusted for age and presence of one or more medical comorbidities were determined by test-negative case-control design to be ?16.8% (90% confidence interval (CI): ?48.9 to 8.3) overall and ?22.0% (90% CI: ?66.5 to 10.7) for laboratory-confirmed influenza A(H3N2). Among adults?aged under?65 years, the overall VE was 10.8% (90% CI: ?50.2 to 47.0) while in adults?aged 65 years or older, the overall VE was ?25.4% (90% CI: ?65.0 to 4.6). .

Interim estimates of 2013/14 influenza clinical severity and vaccine effectiveness in the prevention of laboratory-confirmed influenza-related hospitalisation, Canada, February 2014

During the 2013/14 influenza season in Canada, 631 of 654 hospitalisations for laboratory-confirmed influenza enrolled in sentinel hospitals were due to Influenza A. Of the 375 with known subtype, influenza A(H1N1) accounted for 357. Interim unmatched vaccine effectiveness adjusted for age and presence of one or more medical comorbidities was determined by test-negative case-control design to be 58.5% (90% confidence interval (CI): 43.9-69.3%) overall and 57.9% (90% CI: 37.7-71.5) for confirmed influenza A(H1N1).

Safety, immunogenicity, and tolerability of three influenza vaccines in older adults: results of a randomized, controlled comparison.

To determine if newer influenza vaccines can safely improve seroprotection rates of older adults, we compared three licensed trivalent inactivated vaccines (TIVs) in a randomized, controlled trial with evaluator blinding. Participants were non-frail adults ≥ 65 y old, annually TIV-immunized. Study vaccines included intradermal (IDV), MF59-adjuvanted (ADV) and subunit (TIV) formulations of equal potency and strain composition. Blood was obtained before vaccination (V1) and 21 (V2) and 180 d (V3) afterward and tested by hemagglutination inhibition (HAI) assay. Safety diaries were completed daily by participants and specific tolerability questions were posed regarding injections and symptoms. In total, 911 participants were immunized and 887 (97.4%) completed V3. Groups had similar demographics. General symptom rates post-vaccination were similar among groups. Rates of injection site redness after IDV/ADV/TIV were 75%/13%/13% and rates of pain were 29%/38%/20%, respectively, but each vaccine was well tolerated, with symptoms causing little bother. Baseline antibody titers did not differ significantly among groups but B/Brisbane titers were too high for meaningful response assessments. At V2, seroprotection rates (HAI titer ≥ 40) were highest after ADV, the rate advantage over IDV and TIV being significant at 11.8% and 11.4% for H3N2 and 10.2% and 12.5% for H1N1, respectively. At day 180, seroprotection rates had declined ~25% and no longer differed significantly among groups. While IDV and TIV were also well tolerated, ADV induced modestly higher antibody titers in seniors to influenza A strains at 3 weeks but not 6 months post-vaccination. Immune responses to IDV and TIV were similar in this population.