Search

Background: After pandemic, A(H1N1)pdm09 is generally known to be associated with younger adults' infection and greater severity than seasonal A(H3N2) but some inconsistences between recent studies exist. Objectives: We aimed to compare the epidemiology and clinical outcomes of A(H1N1)pdm09 and A(H3N2) to verify and consolidate about the knowledge of known differences of subtypes. Methods: Data were retrospectively collected from the hospital‐based influenza morbidity and mortality surveillance in South Korea in nine tertiary care hospitals, from August 31, 2014, to August 25, 2018. Patients with H1N1pdm09 or H3N2 infection admitted in the emergency room or ward were recruited. Results: A total of 1747 patients had influenza A and were divided into two groups those with A(H1N1)pdm09 (n = 240) and those with A(H3N2) (n = 1507). A(H1N1)pdm09 group had younger age (mean age ± standard deviation 50.0 ± 18.8 in H1N1 vs 53.4 ± 21.1 in H3N2, P =.030), lower influenza vaccination (27.9% vs 43.9%, P <.001) and pneumococcal vaccination rates (41.0% vs 51.9%, P <.001), and fewer underlying diseases (67.5% vs 74.0%, P =.035) than the A(H3N2) group. Influenza A subtypes were not associated with pneumonia risk (adjusted odds ratios [AOR] of A(H1N1)pdm09: 0.7 [95% confidence interval [CI]: 0.4‐1.2, P =.172]) and in‐hospital mortality (hazard ratio (HR) of A(H1N1)pdm09: 1.0 (95% CI: 0.3‐3.1, P =.983)). Influenza vaccination reduced in‐hospital mortality in hospitalized patients (HR: 0.3 (95% CI: 0.1‐0.7), P =.005). Conclusions: A(H1N1)pdm09 infection was more common in younger patients without significant difference in pneumonia risk and in‐hospital mortality between subtypes. Influenza vaccination was associated with reduced in‐hospital mortality. [ABSTRACT FROM AUTHOR]

Neuraminidase inhibitors (NAIs) are widely used antiviral drugs for the treatment of humans with influenza virus infections. There have been widespread reports of NAI resistance among seasonal A(H1N1) viruses, and most have been identified in oseltamivir-exposed patients or those treated with other NAIs. Thus, monitoring and identifying NA markers conferring resistance to NAIs--particularly newly introduced treatments--is critical to manage viral infections. Therefore, we screened and identified substitutions conferring resistance to laninamivir by enriching random mutations in the NA gene of the 2009 pandemic influenza A(H1N1)pdm09] followed by deep sequencing of the laninamivir-selected variants. After the generation of single mutants possessing each identified mutation, two A(H1N1)pdm09 recombinants possessing novel NA gene substitutions (ie, D199E and P458T) were shown to confer resistance to more than one NAI. Of note, mutants possessing P458T--which is located outside of the catalytic or framework residue of the NA active site--exhibited highly reduced inhibition by all four approved NAIs. Using MDCK cells, we observed that the in vitro viral replication of the two recombinants was lower compared with WT. Additionally, in infected mice, decreased mortality and/or mean lung viral titers were observed in mutants compared with WT. Reverse mutations to WT were observed in the lung homogenate samples from D199E-infected mice after 3 serial passages. Overall, the novel NA substitutions identified which could possibly emerge in influenza A(H1N1)pdm09 during laninamivir therapy and have altered NAI susceptibility, but the compromised in vitro/in vivo viral fitness may limit viral spreading. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study that examines the concurrence of active pulmonary tuberculosis (TB) and influenza A(H1N1)pdm09 virus infection in South Korea. The study shows the sensitivity to anti-TB drugs by all Mycobacterium tuberculosis isolates. Lifetime risk for development of active TB is 5 percent to 10 percent for persons infected with Mycobacterium tuberculosis and increases for those with immunocopromising conditions.

Abstract: The 2009 influenza pandemic was caused by a novel triple-reassortant influenza A/H1N1 virus that was further recombined with a Eurasian pig flu virus. Vaccination is a key countermeasure for disease; however, little data assessing vaccine effectiveness (VE) against the pandemic H1N1 virus are available. We conducted a matched case–control study to assess effectiveness of the 2009 influenza A/H1N1 monovalent vaccine against laboratory-confirmed, medically attended influenza patients. Subjects included in the study were ≥10 years of age and were treated at five university hospitals in the Republic of Korea (ROK) from December 2009 through March 2010. For subjects visiting outpatient clinics with influenza-like illness (ILI), real time reverse transcription polymerase chain reaction (rRT-PCR) was used to diagnose 2009 H1N1 influenza virus infection. Subjects with positive rRT-PCR were classified as cases, while those testing negative were controls. A valid vaccination corresponded to ≥14 days between receiving a dose of vaccine and symptom onset. Overall, 416 ILI subjects were analyzed, and 60 (14.4%) were vaccinated with the 2009 influenza A/H1N1 monovalent vaccine. The overall VE against pandemic 2009 A/H1N1 virus illness after adjustment for age group and presence of chronic medical conditions was 73.4% (95% confidence interval [CI]=49.1–86.1%). Both vaccine formulations (unadjuvanted and MF-59 adjuvanted) showed a statistically significant VE. In conclusion, the 2009 influenza A/H1N1 monovalent vaccine was substantially protective against pandemic influenza in the ROK during the 2009–2010 season. [Copyright &y& Elsevier]

Abstract: In a pandemic, the development of an effective influenza vaccine is the most important subject from the view of public health. This study was performed to evaluate the immunogenicity and safety of inactivated, monovalent H1N1 2009 vaccine (Green Cross Corporation, Yongin, Korea) among healthy adults aged 19–64 years (Group 1) and the elderly aged ≥65 years (Group 2) in a two-dose regimen, 21 days apart. At baseline, 28 of 454 participants (6.1%) had hemagglutination-inhibition titers of ≥1:40 with no significant difference between age groups (p =0.27). There was an apparent dose-dependent antibody response; participants receiving the dose of 30μg hemagglutinin (HA) showed higher geometric mean titers (GMTs) than the 15μg HA group in both age groups. Despite the rates of seroprotection and seroconversion were significantly higher with 30μg HA formulation than 15μg HA formula in Group 2, there was no definite difference in Group 1 irrespective of vaccine formula. Significant GMT elevation after the second dose was not noted in either age group, regardless vaccine formulations. No deaths, vaccine-related serious adverse events, or immediate unsolicited adverse reactions occurred during the study periods. [Copyright &y& Elsevier]