Influenza C virus–associated community-acquired pneumonia in children

To evaluate the impact of influenza C (ICV) infection in children with community-acquired pneumonia (CAP), all of the children consecutively seen during 4 influenza seasons with respiratory symptoms and radiographically confirmed CAP were prospectively evaluated. ICV was identified in the respiratory secretions of five of 391 patients (1·3%). In children with ICV-associated CAP, clinical data were similar to those observed in children with IAV-associated CAP and worse than those observed in children with IBV-associated. The phylogenetic tree showed that the sequenced strains clustered in two of the six ICV lineages. These findings highlight that ICV can be a cause of CAP of children and that this can be severe enough to require hospitalization.

Detection of influenza C virus by a real-time RT-PCR assay

BACKGROUND

Influenza C virus can cause both upper and lower respiratory tract infections and has been reported to be prevalent in children. However, these infections have been under-diagnosed, and epidemiological data available are limited due to the lack of convenient detection assays.

OBJECTIVE

Design and validate a real-time reverse-transcriptase PCR (rt RT-PCR) assay for the detection of influenza C.

STUDY DESIGN

Respiratory samples from two primary settings, namely, children who were hospitalized or seen in the emergency department, and respiratory outbreaks for which no other viral etiology was found were used for the detection of influenza C.

RESULTS AND CONCLUSIONS

The assay was sensitive and specific for the detection of influenza C. Eleven of 474 (2·32%) patients, all less than 10 years of age, were positive for influenza C. The strains clustered into two lineages, namely C/Kanagawa and C/Sao Paulo, based upon sequencing of the hemagglutinin-esterase gene. Epidemiological data showed that a higher proportion of influenza C infections occur in younger children and during the winter months. This is the first report of the detection of influenza C in Alberta, Canada, and suggests that the detection of this virus should be included in respiratory virus testing panels.

Prospective study of influenza C in hospitalized children

We present a prospective study of influenza C virus infections in hospitalized children in Spain during 6 years, including the pandemic influenza A (H1N1) pdm. Influenza C infections accounted for 13.3% of influenza-positive cases. The patients with simple influenza C infection were clinically similar to other influenza types, but a high rate of coinfection (81%) makes it difficult to assess its clinical role.

Isolation of a novel swine influenza virus from Oklahoma in 2011 which is distantly related to human influenza C viruses

Of the Orthomyxoviridae family of viruses, only influenza A viruses are thought to exist as multiple subtypes and has non-human maintenance hosts. In April 2011, nasal swabs were collected for virus isolation from pigs exhibiting influenza-like illness. Subsequent electron microscopic, biochemical, and genetic studies identified an orthomyxovirus with seven RNA segments exhibiting approximately 50% overall amino acid identity to human influenza C virus. Based on its genetic organizational similarities to influenza C viruses this virus has been provisionally designated C/Oklahoma/1334/2011 (C/OK). Phylogenetic analysis of the predicted viral proteins found that the divergence between C/OK and human influenza C viruses was similar to that observed between influenza A and B viruses. No cross reactivity was observed between C/OK and human influenza C viruses using hemagglutination inhibition (HI) assays. Additionally, screening of pig and human serum samples found that 9.5% and 1.3%, respectively, of individuals had measurable HI antibody titers to C/OK virus. C/OK virus was able to infect both ferrets and pigs and transmit to naive animals by direct contact. Cell culture studies showed that C/OK virus displayed a broader cellular tropism than a human influenza C virus. The observed difference in cellular tropism was further supported by structural analysis showing that hemagglutinin esterase (HE) proteins between two viruses have conserved enzymatic but divergent receptor-binding sites. These results suggest that C/OK virus represents a new subtype of influenza C viruses that currently circulates in pigs that has not been recognized previously. The presence of multiple subtypes of co-circulating influenza C viruses raises the possibility of reassortment and antigenic shift as mechanisms of influenza C virus evolution.

Influenza surveillance among children with pneumonia admitted to a district hospital in coastal Kenya, 2007-2010

BACKGROUND

Influenza data gaps in sub-Saharan Africa include incidence, case fatality, seasonal patterns, and associations with prevalent disorders.

METHODS

Nasopharyngeal samples from children aged <12 years who were admitted to Kilifi District Hospital during 2007-2010 with severe or very severe pneumonia and resided in the local demographic surveillance system were screened for influenza A, B, and C viruses by molecular methods. Outpatient children provided comparative data.

RESULTS

Of 2002 admissions, influenza A virus infection was diagnosed in 3.5% (71), influenza B virus infection, in 0.9% (19); and influenza C virus infection, in 0.8% (11 of 1404 tested). Four patients with influenza died. Among outpatients, 13 of 331 (3.9%) with acute respiratory infection and 1 of 196 without acute respiratory infection were influenza positive. The annual incidence of severe or very severe pneumonia, of influenza (any type), and of influenza A, was 1321, 60, and 43 cases per 100,000 <5 years of age, respectively. Peak occurrence was in quarters 3-4 each year, and approximately 50% of cases involved infants: temporal association with bacteremia was absent. Hypoxia was more frequent among pneumonia cases involving influenza (odds ratio, 1.78; 95% confidence interval, 1.04-1.96). Influenza A virus subtypes were seasonal H3N2 (57%), seasonal H1N1 (12%), and 2009 pandemic H1N1 (7%).

CONCLUSIONS

The burden of influenza was small during 2007-2010 in this pediatric hospital in Kenya. Influenza A virus subtype H3N2 predominated, and 2009 pandemic influenza A virus subtype H1N1 had little impact.

Detection and quantification of influenza C virus in pediatric respiratory specimens by real-time PCR and comparison with infectious viral counts

BACKGROUND

The epidemiological and clinical impacts of influenza C virus infection may have been underestimated by conventional viral culture screening alone.

OBJECTIVE

To evaluate a newly developed real-time polymerase chain reaction (PCR) assay as a tool for diagnosing influenza C virus infection.

STUDY DESIGN

The primers and probe for real-time PCR were designed to amplify the conserved region of the nucleoprotein gene based on the aligned sequences of nine isolates from 1967 to 2010. Respiratory specimens from children collected between January 2010 and August 2010 were examined for the presence of influenza C virus by cell culture and real-time PCR. Specimens that were positive for the virus using real-time PCR were further examined using an infectivity assay with embryonated hen's eggs.

RESULTS

Of the 1203 specimens examined, 34 (2.8%) tested positive for the influenza C virus by cell culture and 51 (4.2%) tested positive by real-time PCR. The mean viral load and infectivity titer in specimens that tested positive using cell culture were 3.97×10(8)copies/ml and 5.43×10(5)EID(50)/ml, respectively, and those in specimens that were negative using cell culture were 2.18×10(6)copies/ml and 3.67×10(2)EID(50)/ml, respectively. In the clinical specimens with viral loads less than 10(5)copies/ml, it was not possible to isolate the virus using embryonated hen's eggs. The copy number-to-EID(50) ratio of the clinical specimens was much higher, ranging from 32 to 278,000, than those of culture fluid, ranging from 2.3 to 13.5.

CONCLUSION

The real-time PCR assay described here can be used as a sensitive method for diagnosing influenza C virus infection.

Influenza C virus surveillance during the first influenza A (H1N1) 2009 pandemic wave in Catalonia, Spain

Although particular attention is paid to influenza A and B virus isolates during influenza surveillance, influenza C virus (FLUCV) coexisted during the first influenza A (H1N1) 2009 pandemic wave during the 2009-2010 season. From 27 April 2009 to 9 May 2010, 12 strains of FLUCV were detected in specimens collected from 1713 nonhospitalized patients with upper respiratory tract illness using a molecular method. Half of the patients with FLUCV infection were older than 14 years. The most frequent symptoms were cough and fever, similar to other viral respiratory infections. Phylogenetic analysis of the hemagglutinin-esterase gene revealed that the strains belonged to the C/Kanagawa/1/76-related and C/Sao Paulo/378/82-related lineages, demonstrating their co-circulation in Catalonia. In addition to regular virological surveillance that provides information about the incidence and the exact role of FLUCV in acute viral respiratory infections in the general population, the genetic lineage identification offers additional data for epidemiological purposes.

Tracking the emergence of pandemic Influenza A/H1N1/2009 and its interaction with seasonal influenza viruses in Singapore

INTRODUCTION

Since the emergence of the pandemic influenza A/H1N1/2009 virus in April 2009, diagnostic testing in many countries has revealed the rapid displacement and then replacement of circulating seasonal influenza viruses by this novel virus.

MATERIALS AND METHODS

In-house seasonal and pandemic influenza-specific polymerase chain reaction assays were introduced and/or developed at the Molecular Diagnosis Centre (MDC) at the National University Hospital (NUH), Singapore. These assays have been used to test all samples received from in-patients, out-patients, staff and visitors for suspected pandemic influenza A/H1N1/2009 infection.

RESULTS

Prior to the arrival of the pandemic A/H1N1/2009 virus in Singapore at the end of May 2009, seasonal influenza A/H3N2 predominated in this population, with very little seasonal influenza A/H1N1 and B viruses detected. Within about 1 month of its arrival in Singapore (mainly during June to July 2009), this pandemic virus rapidly displaced seasonal influenza A/H3N2 to become the predominant strain in the Singaporean population served by MDC/NUH.

CONCLUSIONS

Realtime molecular techniques have allowed the prompt detection of different influenza subtypes during this current pandemic, which has revealed the displacement/replacement of previously circulating seasonal subtypes with A/H1N1/2009. Although some of this may be explained by immunological cross-reactivity between influenza subtypes, more studies are required.

Study of influenza C virus infection in France

From November 2004 to April 2007, specimens were obtained from 2,281 patients with acute respiratory tract illness in Normandy, France. Eighteen strains of influenza C virus were detected in these samples using a combined tissue culture/RT-PCR diagnostic method. Most patients with influenza C virus infection (13/18) were infants or young children (<2 years of age). The most frequent symptoms were fever and cough, and the clinical presentation of influenza C virus infection was similar to that of other respiratory viruses. Thirteen of the 18 infected patients were hospitalized; 3 presented with a severe lower respiratory infection. The hemagglutinin-esterase (HE) gene of 10 isolates was sequenced to determine the lineages of the circulating influenza C viruses. Phylogenetic analysis revealed that most of the isolated strains had an HE gene belonging to the C/Yamagata/26/81-related lineage. These results show that influenza C virus regularly circulates in Normandy and generally causes a mild upper respiratory infection. Because the differential clinical diagnosis of influenza C virus infection is not always easy, it is important to identify viral strains for both patient management and epidemiological purposes.

A nationwide epidemic of influenza C virus infection in Japan in 2004

During the period from January to July 2004, a total of 131 influenza C viruses were detected by cell culture or reverse transcription-PCR (RT-PCR) from specimens that were obtained from children with acute respiratory symptoms in 10 prefectures across Japan. Influenza C virus was identified most frequently in the Miyagi (1.4%, 45 of 3,226 specimens) and Yamagata (2.5%, 31 of 1,263 specimens) prefectures, and the frequency in this year was the highest since 1990. Phylogenetic analysis of the hemagglutinin esterase gene of the 13 strains isolated in nine prefectures revealed that genetically similar strains belonging to the Kanagawa/1/76-related lineage dominantly spread throughout Japan. During the 2004 influenza season, influenza C virus coexisted with epidemics of influenza A virus (H3 strain), and 12 cases were identified from patients who had been diagnosed with influenza-like illness (7 were detected by RT-PCR, and 5 were detected by culture). A comparison of specimens that were found positive by culture with those found positive only by RT-PCR shows that the amount of virus in PCR-positive specimens tended to be lower than in isolation-positive specimens. Although the mean peak temperature in patients in the PCR-positive group was slightly lower, there were no significant differences in characteristics between specimens (i.e., kind of specimen, period from onset to specimen collection, age distribution of patients, and severity of illness). These results suggest that an epidemic of influenza C virus occurred on a national scale during this period and that RT-PCR can be an effective supplemental tool for the evaluation of clinical and epidemiological information.

Clinical features of influenza C virus infection in children

BACKGROUND

Seroepidemiological studies have revealed that influenza C virus is widely distributed globally. However, because the isolation of this virus is difficult, there have been few reports on its clinical features.

METHODS

Between December 1990 and November 2004, 84,946 respiratory-tract specimens were obtained from patients < or = 15 years old. On the basis of the results of isolation of virus, we examined the clinical data on children infected with influenza C virus.

RESULTS

Of 170 children infected with influenza C virus, 157 (92.4%) were < 6 years old. Fever (frequency, 90.0%), cough (frequency, 74.1%), and rhinorrhea (frequency, 61.8%) were the most frequent symptoms. The mean duration of fever was 2.88 days (standard deviation, 1.66 days). Of the 170 children, 29 were hospitalized, and 21 (72.4%) of these 29 had lower-respiratory-tract illness such as pneumonia, bronchitis, and bronchiolitis. The rate of hospital admission was significantly higher in children < 2 years old than in children 2-5 years old (30.4% vs. 11.9%; P = .0043).

CONCLUSIONS

Influenza C virus is a significant cause of upper-respiratory-tract illness in children < 6 years old, and the risk of complications with lower-respiratory-tract illness is particularly high in children < 2 years old.

Development of three multiplex RT-PCR assays for the detection of 12 respiratory RNA viruses

Three multiplex hemi-nested RT-PCR assays were developed to detect simultaneously 12 RNA respiratory viruses: influenza viruses A, B and C, human respiratory syncytial virus (hRSV), human metapneumovirus (hMPV), parainfluenza virus types 1-4 (PIV-1, -2, -3 and -4), human coronavirus OC43 and 229E (HCoV) and rhinovirus (hRV). An internal amplification control was included in one of the RT-PCR assays. The RT-PCR multiplex 1 and the hemi-nested multiplex 1 detected 1 and 0.1 TCID50 of RSV A, respectively, and 0.01 and 0.001 TCID50 of influenza virus A/H3N2, respectively. Two hundred and three nasal aspirates from hospitalised children were retrospectively tested in comparison with two conventional methods: direct immunofluorescence assay and viral isolation technique. Almost all samples (89/91) that were positive by immunofluorescence assay and/or viral isolation technique were detected by the multiplex assay. This method also detected an additional 85 viruses and 33 co-infections. The overall sensitivity (98%), rapidity and enhanced efficiency of these multiplex hemi-nested RT-PCR assays suggest that they would be a significant improvement over conventional methods for the detection of a broad spectrum of respiratory viruses.

Isolation of an influenza C virus introduced into Japan by a traveler from Malaysia

An influenza C virus was isolated from a Japanese traveler who had visited Malaysia in April 1999. Phylogenetic analysis indicated that the genome composition of this virus was distinct from that of any other strain isolated in Japan. The possibility that a genetically unique influenza C virus was introduced into Japan by a traveler is shown.

Characterization of antigenically and genetically similar influenza C viruses isolated in Japan during the 1999-2000 season

Between October 1999 and May 2000, a total of 28 strains of influenza C virus were isolated in four Japanese prefectures: Yamagata, Miyagi, Saitama and Hiroshima. Antigenic analysis showed that the 28 isolates were divided into three distinct antigenic groups, and viruses belonging to different antigenic groups were co-circulating in each of the four prefectures. Phylogenetic analysis of the seven protein genes demonstrated that the viruses having a similar genome composition spread in various areas of Japan during the same period. Furthermore, phylogenetic analysis showed that most of the influenza C viruses isolated in various areas of the world between the 1970s and 1980s were closely related to the contemporary Japanese viruses in all gene segments. These observations suggest that the influenza C viruses cause epidemics in some communities during the same season and that antigenically and genetically similar influenza C viruses spread throughout Japan and may be circulating worldwide.

[Influenza C virus isolated in Hiroshima Prefecture during the 1999/2000 winter season--a clinical and epidemiological study]

Influenza C virus (Inf. C) is one of pathogens of human respiratory tract infection and prevalent throughout the world at an early stage in life. However, Inf. C has been isolated only accidentally and there have been few reports on its clinical and epidemiological features. From November 1999 to March 2000, Inf. C was isolated from clinical specimens (throat swabs) of 4 pediataric patients with respiratory tract illness at Hiroshima Prefectural Hospital and was isolated in 4 peditaric patients at the other medical institutions in Hiroshima prefecture. There were no differences in clinical features including duration of illness, duration of fever, maximum body temperature between 4 patients with Inf. C infection and patients with influenza A (H1N1 and H3N2) and influenza B infection from 1992 to 2000. We investigated geographical distribution of patients with inf. C infection and analyzed for antigenic characteristics with a set of monoclonal antibodies against hemagglutinin-esterase glycoproteins. The data suggested that at least two antigenically different Inf. C prevalented in a region during winter from 1999 to 2000.

[Present data on influenza virus isolated from ducks and chickens, and influenza virus C. Anti-influenza drugs]

Present data on influenza virus isolated from ducks and chickens, and influenza virus C. Anti-influenza drugs. Within the broad field of Glycopathology and Glycotherapeutics, research on influenza virus types A, B and C from humans and several bird species (particularly migratory birds such as ducks, since they are reservoirs for viruses), as well as the search for improved drugs designed for the prevention or treatment of epidemics/pandemics produced by most of those viruses are issues of relevant interest not only from a scientific point of view but also for repercussions on health and the important economical consequences. The research work begun by the author and collaborators at the Department of Biochemistry and Molecular Biology of the University of Salamanca (Spain) in the middle of the 1970's, developed later in close cooperation with the "(Unité d'Ecologie Virale" of the Pasteur Institute of Paris (Prof. Claude Hannoun and collaborators), has been published in about twenty papers that mainly focus on the theoretic-experimental study of: The sialidase (neuraminidase) activity of human influenza viruses types A and B. The acetylesterase activity of type C virus from humans and dogs. The sialidase activity of type A virus from ducks and pigs, in comparison with that of humans. Certain sialidase inhibitors as useful anti-influenza drugs, especially in the case of possible future influenza pandemics of avian origin.

Simultaneous detection of influenza A, B, and C viruses, respiratory syncytial virus, and adenoviruses in clinical samples by multiplex reverse transcription nested-PCR assay

The clinical presentation of infections caused by the heterogeneous group of the respiratory viruses can be very similar. Thus, the implementation of virological assays that rapidly identify the most important viruses involved is of great interest. A new multiplex reverse transcription nested-polymerase chain reaction (RT-PCR) assay that is able to detect and type different respiratory viruses simultaneously is described. Primer sets were targeted to conserved regions of nucleoprotein genes of the influenza viruses, fusion protein genes of respiratory syncytial viruses (RSV), and hexon protein genes of adenoviruses. Individual influenza A, B, and C viruses, RSV (A and B), and a generic detection of the 48 serotypes of adenoviruses were identified and differentiated by the size of the PCR products. An internal amplification control was included in the reaction mixture to exclude false-negative results due to sample inhibitors and/or extraction failure. Detection levels of 0.1 and 0.01 TCID50 of influenza A and B viruses and 1-10 molecules of cloned amplified products of influenza C virus, RSV A and B, and adenovirus serotype 1 were achieved. The specificity was checked using specimens containing other respiratory viruses and no amplified products were detected in any case. A panel of 290 respiratory specimens from the 1999-2000 and 2000-2001 seasons was used to validate the assay. Accurately amplifying RNA from influenza and RSV prototype strains and DNA from all adenovirus serotypes demonstrates the use of this method for both laboratory routine diagnosis and surveillance of all these viruses.

Antigenic and genetic characterization of influenza C viruses which caused two outbreaks in Yamagata City, Japan, in 1996 and 1998

During the 3 years from January 1996 to December 1998, a total of 33 strains of influenza C virus were isolated from 10,726 throat swab specimens collected from children with acute respiratory illness who visited two pediatric clinics in Yamagata City, Japan. These 33 strains were isolated in clusters during two different periods, 20 strains in May to August 1996 and the remaining 13 in March to June 1998. Antigenic analysis with monoclonal antibodies to the hemagglutinin-esterase (HE) glycoprotein and phylogenetic analysis of seven RNA segments showed that the 33 influenza C viruses isolated were antigenically and genetically similar and that they were reassortant viruses which had obtained PB2, PB1, HE, M, and NS genes from a C/pig/Beijing/115/81-like virus and P3 and NP genes from a C/Mississippi/80-like virus. These observations suggest strongly that during the survey period of 3 years, two outbreaks of influenza C occurred in Yamagata City, both of which were caused by a reassortant virus having the genome composition described above.

Evaluation of a single-step multiplex RT-PCR for influenza virus type and subtype detection in respiratory samples

A single-step multiplex reverse transcription-polymerase chain reaction (RT-PCR) for the simultaneous detection of influenza virus type and subtypes was evaluated for its use in clinical specimens. One part of each specimen was tested using an established standard culture and/or monoclonal antibody-based immunofluorescence assay method, and the other part was tested by the multiplex RT-PCR method for the presence or absence of the influenza virus, and its type and subtype. Sixty-seven specimens were examined. The results revealed a strong agreement between the data obtained by the established method and those obtained by the multiplex RT-PCR.