Genetic evolution of influenza A (H3N2) virus in Hangzhou between 2012 and 2017 / 中华微生物学和免疫学杂志

Objective To analyze the prevalence of influenza A (H3N2) virus in Hangzhou be-tween 2012 and 2017 and to investigate the genetic variations in hemagglutinin ( HA) and neuraminidase ( NA) . -ethods Throat swab samples were collected for viral isolation from 12185 patients with suspected influenza in Hangzhou area from January 2012 to December 2017. Influenza virus subtypes were identified by real-time RT-PCR. HA and NA genes of some isolated Influenza A (H3N2) viruses were amplified with spe-cific primers and then analyzed by sequencing and phylogenetic analysis. Results Influenza A (H3N2) virus was the predominant subtype circulating in Hangzhou during 2012 to 2017. It caused high morbidity in elderly people (Z=81. 039, P<0. 05). Most of the isolated influenza A (H3N2) viruses belonged to the phylogenetic clades of 3C. 3a and 3C. 2a. These viruses shared a homology of 96. 7％-100％ in nucleotide sequences of both HA and NA genes, but possessed several HA and NA mutations in antigenic sites. Con-clusions Influenza A (H3N2) virus was an important pathogen causing influenza epidemics in Hangzhou during 2012 to 2017. HA and NA genes showed many mutations in antigenic sites. No drug resistant virus was reported.

The influenza season 2016/17 in Bucharest, Romania - surveillance data and clinical characteristics of patients with influenza-like illness admitted to a tertiary infectious diseases hospital

ABSTRACT Background: Influenza continues to drive seasonal morbidity, particularly in settings with low vaccine coverage. Objectives: To describe the influenza cases and viral circulation among hospitalized patients. Methods: A prospective study based on active surveillance of inpatients with influenza-like illness from a tertiary hospital in Bucharest, Romania, in the season 2016/17. Results: A total of 446 patients were tested, with a balanced gender distribution. Overall, 192 (43%) patients tested positive for influenza, with the highest positivity rate in the age groups 3-13 years and >65 years. Peak activity occurred between weeks 1 and 16/2017, with biphasic distribution: A viruses were replaced by B viruses from week 9/2017; B viruses predominated (66.1%). Among the 133 (69.3%) subtyped samples, all influenza A were subtype H3 (n = 57) and all influenza B were B/Victoria (n = 76). Patients who tested positive for influenza presented fewer comorbidities (p = 0.012), except for the elderly, in whom influenza was more common in patients with comorbidities (p = 0.050). Disease evolution was generally favorable under antiviral treatment. The length of hospital stay was slightly longer in patients with influenza-like illness who tested patients negative for influenza (p = 0.031). Conclusions: Distinctive co-circulation of A/H3 and B/Victoria in Bucharest, Romania in the 2016/17 influenza season was found. While the A/H3 subtype was predominant throughout Europe that season, B/Victoria appears to have circulated specifically in Romania and the Eastern European region, predominantly affecting preschoolers and school children.

Influenza virus genotypes circulating in and around Lucknow, Uttar Pradesh, India, during post pandemic period, August 2010 - September 2012.

Background & objectives: During the post influenza pandemic period, continuous surveillance of influenza virus and its subtypes is mandatory to help the policy makers to take effective and appropriate decisions. Therefore, this study was planned to determine the pattern of influenza virus activity in context to various meteorological and clinical parameters in and around Lucknow, Uttar Pradesh, India, during post pandemic period August 2010 - September 2012. Methods: Nasal swabs/throat swabs/nasopharyngeal aspirates of 2669 patients were collected. One-step real time PCR for detection of influenza virus was done according to the Centers for Disease Control and Prevention (CDC) protocol. Results: Influenza positivity was 15.8 per cent (423/2669) in symptomatic patients. Of the 423 total positives, 192 (7.2%) were influenza A and 231 (8.7%) were influenza B. Positivity for influenza virus was significantly (P=0.001, OR=2.9, CI=1.9-4.3) higher in patients with Influenza like illness (ILI) (17.4%, 396/2271) than those with severe acute respiratory illness (SARI) (6.8%, 27/398). Influenza A positive samples were subtyped as; pdmH1N1 (67.2%, 129/192) and seasonal H3N2 (32.8%, 63/192). It significantly correlated with monthly mean rainfall, humidity and dew point while atmospheric pressure was inversely related. No significant association was found with temperature and wind speed. Clinical variations were observed between different strains of Influenza virus. Interpretation & conclusions: The findings provide a clear picture of different clinical presentations of various strains of influenza A and B viruses and epidemiology of influenza infection from Lucknow (UP), India. The seasonality of influenza virus infection showed variation in relation to different environmental factors. Pandemic H1N1 caused more systemic infection than seasonal influenza A/H3N2 virus.

Traceability of the A/H3N2 virus borne influenza pandemic in Zhejiang province,1998 / 中华流行病学杂志

Objective To trace back to the influenza pandemic caused by A/H3N2 virus happened in Zhejiang province,1998.Methods The whole genome of three isolates related to Zhejiang influenza virus was amplified through RT-PCR,and the identified sequences were aligned with the sequences downloaded from GenBank of the H3N2 strains which were circulating in other regions during 1995 to 1998.The crossing HAI titers of the reference strains were measured by HAI test and antigenic ratios were calculated.Results The Phylogenetic tree,constructed based on HA sequence showed that the dominant strains A/Zhejiang/11/98 and A/Zhejiang/18/98 were significant different from the isolates circulated in other regions during 1995 to 1996 and the strains isolated in the mainland of China,in 1997.Although the A/Zhejiang/11/98 and A/Zhejiang/18/98 strains were distributed in the same cluster with A/Sydney/5/97,the two strains were closer to the epidemic strains isolated in Hong Kong and New York in the later part of 1997.Based on HAI,NA and MP genes,A/Zhejiang/18/98 seemed to be the closest one to the Hong Kong epidemic strains,and the genetic distances between A/Zhejiang/18/98 and New York strains were shorter than that with A/Sydney/5/97 based on PA,HA and NS genes.There were only 1-3 amino acid differences between A/Zhejiang/18/98 and Hong Kong or New York strains,whereas 7 amino acid differences with A/Sydney/5/97,in which three were located in the antigenic determinant regions.Data from the crossing HAI test showed that the antigenic ratio between A/Zhejiang/18/98 and A/Sydney/5/97 had reached 2.0,indicating the antigenic difference to a certain extent.Additionally,the onset of the influenza epidemic during 1997 to 1998 also suggested the possible route of transmission related to this H3N2 virus.Conclusion The influenza pandemic occurred in Zhejiang province in 1998 was possibly caused by the importation of a newly identified H3N2 influenza variant via Hong Kong and New York in late 1997.

Study on the genome sequence of influenza virus subtype A/H3N2 strains circulated in Zhejiang province during 1998 to 2009 / 中华流行病学杂志

Objective To analyze the relationship between influenza epidemic and genetic characteristic on the whole genome of influenza virus subtype A/H3N2 strains isolated in Zhejiang province during 1998 to 2009. Methods All of the eight genes from the 19 Zhejiang influenza virus isolates, circulated during 1998 to 2009, were amplified by RT-PCR and sequenced. The obtained sequences were aligned and analyzed with the vaccine strains being used in the last 10 years.Results The highest mutation happened within HA and NA genes and the amino acid divergent ratios were 13.98% and 10.00%. Amongst the six internal proteins, the amino acid divergent ratios of NP, M2 and NS1 were 6.43%, 6.19% and 3.48% respectively, and the others were lower than 3%.Other than the HA and NA genes, mutations were also observed on six internal genes of the strains isolated in those years when the influenza virus subtype A/H3N2 was widely circulating.Additionally, there had been an obvious genetic lag between vaccine strains recommended by WHO and the contemporary Zhejiang epidemic strains for many years. Conclusion Besides on HA and NA genes, surveillance programs should also be covered mutations regarding the internal genes of influenza virus subtype A/H3N2 strains, in order to provide important information for forecasting and warning of a new round of influenza epidemic.

Two Cases of Influenza-associated Encephalopathy

Influenza-associated encephalopathy is typically associated with a sudden onset of high fever, severe convulsions, rapidly progressive coma and death within 2 or 3 days. It has been actively researched in Japan as it caused a tremendous increase in the number of deaths from 1997 to 2002. But there has been reported only one case in Korea, who was diagnosed on the basis of serologic testing by hemagglutinin inhibition. We report here a 14-month-old boy who was taken supportive care and a 3-year-old girl who was taken amantadine and methyprednisolone pulse therapy. Both of them were admitted under the diagnosis of influenza-associated encephalopathy on the basis of reverse transcription-polymerase chain reaction of nasopharyngeal fluid and cerebrospinal fluidm, brain magnetic resonance imagings. The first case was confirmed by the identification of influenza A/H3N2 in the cerebrospinal fluid culture by RT-PCR for the first time in Korea.

Analysis of Isolation and Subtyping of Influenza Virus in Seoul, During 1999-2003

Influenza is an important public health problem in almost every winter of temperate countries, and is often associated with increased rates of hospitalization and death. In 1999, we started influenza surveillance with 4 voluntary sentinel physicians and the Public Health Center. From 1999 through 2003, 74 influenza viruses were isolated from 738 clinical specimens, which were collected from patients with Influenza like illness (ILI) in Seoul. The case definition for ILI was a fever over 38degrees C and systemic symptoms such as cough, or sore throat. ILI was the highest, 35.5% at the 20~49 age group and the rate of virus isolation was the highest, 20.6% at the 7~19 age group. Among isolated 74 influenza viruses, four of them were identified as A/H3N2 type in 1999-2000 season, seven of them were A/H3N2 in 2000-2001 season, fourteen were A/H1N1 in the 2001-2002 season and others were subtyped as influenza A/H3N2 viruses in the 2002-2003 season. Influenza viruses were collected 18.9% at Seocho-Gu, 18.8% at Dongjak-Gu and 7.6% at KangbukGu etc. and the isolate rate of virus had the area difference; Gwangjin-Gu 66%, Eunpyeong-Gu 65.6% Gangnam-Gu 20.0%, Kangbuk-Gu 19.6%. These findings may contribute towards the recommondation on the influenza vaccine formulation and development of influenza control measure based on the analyzed data.