Epidemiology and molecular characterization of influenza viruses in Burkina Faso,sub‐Saharan Africa

Background

The importance of influenza viruses in respiratory infections in sub‐Saharan Africa has been historically overlooked, including in Burkina Faso.

Objectives

This study therefore aimed at evaluating the prevalence and seasonal occurrence of influenza viruses in children under 5 years old, at risk of influenza‐related complications, presenting with influenza‐like illness (ILI) or severe acute respiratory infection (SARI). The study also aimed at identifying the periods with increased influenza transmission for vaccination recommendations in Burkina Faso.

Methods

From January 2014 to December 2015, ILI and SARI (2015 only) patients were recruited in six healthcare centers in Burkina Faso. Influenza A and B molecular detection and subtyping were performed. Clade clustering of a subset of A(H1N1)pdm09 and A(H3N2) strains was deduced by performing phylogenetic analyses on hemagglutinin gene sequences. Weekly surveillance data from FluNet (2011‐2013; 2016) and this study (2014‐2015) were used to identify periods of increased influenza activity.

Results

Influenza A and B viruses were detected in 15.1% (112 of 743) of ILI and 6.6% (12 of 181) of SARI patients. Overall, influenza A viruses were largely predominant (81 of 124, 65.3%), with 69.1% of A(H3N2) and 30.9% of A(H1N1)pdm09 strains. Four waves of increased transmission were identified in 2014‐2015, each dominated by different influenza subtypes and clades. Between 2011 and 2016, periods of increased influenza activity varied in their frequency, duration, and timing.

Conclusion

Influenza A and B viruses were detected in a substantial number of ILI and SARI cases in Burkina Faso. Vaccination in September‐October would likely protect the highest number of patients.     

Sentinel surveillance of influenza in Burkina Faso: identification of circulating strains during 2010–2012

Background

Although influenza surveillance has recently been improved in some sub-Saharan African countries, no information is yet available from Burkina Faso.

Objectives

Our study was the first to determine the prevalence of influenza viruses circulating in Burkina Faso through a sentinel surveillance system.

Methods

We conducted sentinel surveillance with oropharyngeal (OP) swabs collected from outpatients (1 month to 83 years) from six sites in Bobo-Dioulasso and Ouagadougou, among patients meeting the WHO/CDC case definition for influenza-like illness (ILI; fever ≥38°C, and cough and/or sore throat in the absence of other diagnosis) from July 2010 to May 2012. Influenza viruses were detected by real-time RT-PCR using CDC primers, probes, and protocols.

Results

The first three ILI cases were enrolled each day; of 881 outpatients with ILI enrolled and sampled, 58 (6·6%) tested positive for influenza viruses (29 influenza A and 29 influenza B). Among the influenza A viruses, 55·2% (16/29) were influenza A (H1N1)pdm09 and 44·8% (13/29) were seasonal A (H3N2). No cases of seasonal A/H1N1 were detected. Patients within 0–5 years and 6–14 years were the most affected, comprising 41·4% and 22·4% laboratory-confirmed influenza cases, respectively. Influenza infections occurred during both the dry, dusty Harmattan months from November to March and the rainy season from June to October with peaks in January and August.

Conclusions

This surveillance was the first confirming the circulation of influenza A (H1N1)pdm09, A/H3N2, and influenza B viruses in humans in Burkina Faso.     

Epidemiological study of influenza virus infections in young adult outpatients from Buenos Aires,Argentina

Background Influenza virus is the most common cause of influenza‐like illness (ILI) in adults. In Argentina, studies on influenza and other respiratory viruses were performed mostly in pediatric populations. Objectives To determine: (1) the frequency of influenza virus and other common respiratory viruses in adult outpatients with ILI, (2) whether the signs and symptoms predict viral etiology, (3) whether viral diagnosis changes clinical management or infection control measures and (4) to characterize the influenza strains circulating in the community. Population and methods Nasal and pharyngeal swabs from adult outpatients with ILI attending the emergency room during the winter seasons of 2004 and 2005 in Argentina were evaluated by immunofluorescence and RT‐PCR. Results Of 151 samples analyzed, 39 (26%) were influenza A positive, 5 (3·3%) influenza B positive and 4 (2·6%) respiratory syncytial virus positive by immunofluorescence. Two samples (1·3%) were human metapneumovirus positive by RT PCR. Cell culture detected six additional influenza viruses and one adenovirus positive sample. The sensitivity of immunofluorescence for influenza compared with culture was 70%. Symptoms did not predict etiology. Conclusions In this study, 40% of the patients with ILI had a specific viral infection and 83% were influenza viruses. Viral detection was necessary to determine the etiology as signs and symptoms were not different between patients with or without viral infection. Viral diagnosis was important to implement infectious control measures. Circulating influenza strains in this study were similar to the correspondent vaccine strains selected for the Southern hemisphere.     

Literature review of the epidemiology of influenza B disease in 15 countries in the Asia‐Pacific region

Influenza control strategies focus on the use of trivalent influenza vaccines containing two influenza A virus subtypes and one of the two circulating influenza type B lineages (Yamagata or Victoria). Mismatches between the vaccine B lineage and the circulating lineage have been regularly documented in many countries, including those in the Asia‐Pacific region. We conducted a literature review with the aim of understanding the relative circulation of influenza B viruses in Asia‐Pacific countries. PubMed and Western Pacific Region Index Medicus were searched for relevant articles on influenza type B published since 1990 in English language for 15 Asia‐Pacific countries. Gray literature was also accessed. From 4834 articles identified, 121 full‐text articles were analyzed. Influenza was reported as an important cause of morbidity in the Asia‐Pacific region, affecting all age groups. In all 15 countries, influenza B was identified and associated with between 0% and 92% of laboratory‐confirmed influenza cases in any one season/year. Influenza type B appeared to cause more illness in children aged between 1 and 10 years than in other age groups. Epidemiological data for the two circulating influenza type B lineages remain limited in several countries in the Asia‐Pacific, although the co‐circulation of both lineages was seen in countries where strain surveillance data were available. Mismatches between circulating B lineages and vaccine strains were observed in all countries with available data. The data suggest that a shift from trivalent to quadrivalent seasonal influenza vaccines could provide additional benefits by providing broader protection.     

An early report from newly established laboratory-based influenza surveillance in Lao PDR

Please cite this paper as: Vongphrachanh P, Simmerman JM, Phonekeo D, Pansayavong V, Sisouk T, Ongkhamme S, Bryce GT, Corwin A, Bryant JE. An early report from newly established laboratory-based influenza surveillance in Lao PDR. Influenza and Other Respiratory Viruses 4(2), 47–52. Background Prior to 2007, little information was available about the burden of influenza in Laos. We report data from the first laboratory-based influenza surveillance system established in the Lao People’s Democratic Republic. Methods Three hospitals in the capital city of Vientiane began surveillance for influenza-like illness (ILI) in outpatients in 2007 and expanded to include hospitalized pneumonia patients in 2008. Nasal/throat swab specimens were collected and tested for influenza and other respiratory viruses by multiplex ID-Tag^TM respiratory viral panel (RVP) assay on a Luminex® 100× MAP IS instrument (Qiagen, Singapore). Results During January 2007 to December 2008, 287 of 526 (54·6%) outpatients with ILI were positive for at least one respiratory virus. Influenza was most commonly identified, with 63 (12·0%) influenza A and 92 (17·5%) influenza B positive patients identified. In 2008, six of 79 (7·6%) hospitalized pneumonia patients were positive for influenza A and four (5·1%) were positive for influenza B. Children <5 years represented 19% of viral infections in outpatients and 38% of pneumonia inpatients. Conclusion Our results provide the first documentation of influenza burden among patients with febrile respiratory illness and pneumonia requiring hospitalization in Laos. Implementing laboratory-based influenza surveillance requires substantial investments in infrastructure and training. However, continuing outbreaks of avian influenza A/H5N1 in poultry and emergence of the 2009 influenza A(H1N1) pandemic strain further underscore the importance of establishing and maintaining influenza surveillance in developing countries.     

Burden and outcome of human influenza in a tertiary care hospital of Bangladesh

ObjectiveTo determine the magnitude and outcome of influenza in southern part of Bangladesh and also to identify intrusion of novel influenza virus.MethodsThis study was conducted for two years (2008–2009) in outpatient and inpatient department of both paediatrics and medicine discipline of Khulna Medical College Hospital. Nasal and throat swab specimens were collected from each influenza like illness (ILI) case and kept together in a virus transport media and transported to international centre for diarrhoeal disease and research, Bangladesh laboratory. Influenza virus was detected by rRT-PCR including types and subtypes.ResultsA total of 526 patients were enrolled during the study period with the mean (SD) age of 19 (17) years. Identification of influenza virus was 14% and positive cases were mostly found in under-five children (24%). The vast majority (88%) of influenza cases were found during April to September. Virus detection rate was higher in inpatient department (IPD) (21%) than in outpatient department (12%). The dominant virus type and subtype was influenza A (87%) and H3 (49%), respectively. Type A was significantly higher than type B in causing severe illness compared to ILI (OR=7.04, 95% CI: 2.76–18.7, P<0.01). Headache and chest indrawing was found in significantly higher proportion (P<0.05) in influenza positive IPD cases. Among 31 hospitalized cases majority (77%) recovered completely except two cases that needed referral for additional support.ConclusionsInfluenza mostly affected under-five children and young adult. The peak season here was late summer and rainy season.     

Surveillance of Influenza in Indonesia, 2003–2007

Background Longitudinal data are limited about the circulating strains of influenza viruses and their public health impact in Indonesia. We conducted influenza surveillance among outpatients and hospitalized patients with influenza‐like illness (ILI) across the Indonesian archipelago from 2003 through 2007. Methodology Demographic, clinical data, and respiratory specimens were collected for 4236 ILI patients tested for influenza virus infection by RT‐PCR and viral culture. Principal Findings Influenza A and B viruses co‐circulated year‐round with seasonal peaks in influenza A virus activity during the rainy season (December–January). During 2003–2007, influenza viruses were identified in 20·1% (4236/21 030) of ILI patients, including 20·1% (4015/20 012) of outpatients, and 21·7% (221/1018) of inpatients. One H5N1 case was identified retrospectively in an outpatient with ILI. Antigenic drift in circulating influenza A and B virus strains was detected during the surveillance period in Indonesia. In a few instances, antigenically drifted viruses similar to the World Health Organization (WHO) vaccine strains were detected earlier than the date of their designation by WHO. Conclusions Influenza A and B virus infections are an important cause of influenza‐like illness among outpatients and hospitalized patients in Indonesia. While year‐round circulation of influenza viruses occurs, prevention and control strategies should be focused upon the seasonal peak during rainy season months. Ongoing virologic surveillance and influenza disease burden studies in Indonesia are important priorities to better understand the public health impact of influenza in South‐East Asia and the implications of influenza viral evolution and global spread.     

Sentinel surveillance for influenza and other respiratory viruses in Côte d’Ivoire, 2003–2010

Background Many countries in Africa have lacked sentinel surveillance systems for influenza and are under‐represented in data used for global vaccine strain selection. Objectives We describe 8 years of sentinel surveillance data and the contribution of influenza and other viruses to medically attended influenza‐like illness (ILI) in Côte d’Ivoire. Methods Sentinel surveillance was established in 2003. Nasopharyngeal (NP) specimens and epidemiologic data are collected from persons of all ages presenting with ILI at sentinel sites. Respiratory specimens have been tested for influenza using various viral and molecular diagnostic methods. A subset of 470 specimens collected from children aged 0–5 years were tested for multiple respiratory viruses using RT‐PCR. Results From 2003 to 2010, 5074 NP specimens were collected from patients with ILI. Overall, 969/5074 (19%) of these specimens tested positive for influenza. Seasonal influenza A(H1N1) viruses predominated during 5 years and influenza A(H3N2) viruses predominated during 3 years. Influenza B viruses cocirculated with influenza A viruses during each year from 2004 to 2010. Seasonal peaks in influenza circulation were observed during the months of May, June, and October, with the largest peak corresponding with the primary rainfall season. Of 470 specimens collected from children under aged 5 who were tested for multiple respiratory viruses, a viral respiratory pathogen was detected in 401/470 (85%) of specimens. Commonly detected viruses were RSV (113 of 470 specimens, 24%), rhinoviruses (85/470, 18%), influenza (77/470, 16%), and parainfluenza (75/470, 16%). Conclusion In Côte d’Ivoire, there is a significant annual contribution of influenza and other respiratory viruses to medically attended ILI.     

Influenza: epidemiology, clinical features, therapy, and prevention

Influenza A and B are important causes of respiratory illness in all age groups. Influenza causes seasonal outbreaks globally and, less commonly, pandemics. In the United States, seasonal influenza epidemics account for >200,000 hospitalizations and >30,000 deaths annually. More than 90% of deaths occur in the elderly population. Interestingly, in the novel 2009 H1N1 influenza pandemic, attack rates were highest among children and young adults. Fewer than 10% of cases occurred in adults >60 years old, likely because preexisting antibodies against other H1N1 viruses afforded protection. Despite concerns about a high lethality rate with the novel 2009 H1N1 strain, most illnesses caused by the 2009 H1N1 viruses were mild (overall case fatality rate <0.5%). Clinical features of influenza infection overlap with other respiratory pathogens (particularly viruses). The diagnosis is often delayed due to low suspicion and the limited use of specific diagnostic tests. Rapid diagnostic tests are widely available and allow detection of influenza antigen in respiratory secretions within 1 hour; however, sensitivity ranges from 50 to 90%. Neuraminidase inhibitors (NAIs) (eg, oseltamivir and zanamivir) are effective for treating influenza A or B and for prophylaxis in selected adults and children. Resistance to NAIs is rare, but influenza strains resistant to oseltamivir have been detected. Vaccines are the cornerstone of influenza control. Currently, trivalent inactivated vaccine (TIV) and live attenuated influenza vaccine (LAIV) are available. These agents reduce mortality and morbidity in high-risk patients (i.e., the elderly or patients with comorbidities), and expanding the use of vaccines to healthy children and adults reduces the incidence of influenza, pneumonia, and hospitalizations due to respiratory illnesses in the community.     

Burden of pediatric influenza A virus infection post swine-flu H1N1 pandemic in Egypt

ObjectiveTo screen children with influenza like illness or with symptoms of acute respiratory tract infections for influenza A virus infection — post swine flu pandemic era — using rapid influenza diagnostic tests.MethodsDuring two years (2010 & 2011), 1 200 children with influenza like illness or acute respiratory tract infections (according to World Health Organization criteria) were recruited. Their ages ranged from 2-60 months. Nasopharyngeal aspirates specimens were collected from all children for rapid influenza A diagnostic test.ResultsInfluenza A virus rapid test was positive in 47.5% of the children; the majority (89.6%) were presented with lower respiratory tract infections. Respiratory rate and temperature were significantly higher among positive rapid influenza test patients.ConclusionsInfluenza A virus infection is still a major cause of respiratory tract infections in Egyptian children. It should be considered in all cases with cough and febrile episodes and influenza like symptoms even post swine flu pandemic.     

Spotlight influenza: Extending influenza surveillance to detect non-influenza respiratory viruses of public health relevance: analysis of surveillance data,Belgium, 2015 to 2019

BackgroundSeasonal influenza-like illness (ILI) affects millions of people yearly. Severe acute respiratory infections (SARI), mainly influenza, are a leading cause of hospitalisation and mortality. Increasing evidence indicates that non-influenza respiratory viruses (NIRV) also contribute to the burden of SARI. In Belgium, SARI surveillance by a network of sentinel hospitals has been ongoing since 2011.AimWe report the results of using in-house multiplex qPCR for the detection of a flexible panel of viruses in respiratory ILI and SARI samples and the estimated incidence rates of SARI associated with each virus.MethodsWe defined ILI as an illness with onset of fever and cough or dyspnoea. SARI was defined as an illness requiring hospitalisation with onset of fever and cough or dyspnoea within the previous 10 days. Samples were collected in four winter seasons and tested by multiplex qPCR for influenza virus and NIRV. Using catchment population estimates, we calculated incidence rates of SARI associated with each virus.ResultsOne third of the SARI cases were positive for NIRV, reaching 49.4% among children younger than 15 years. In children younger than 5 years, incidence rates of NIRV-associated SARI were twice that of influenza (103.5 vs 57.6/100,000 person-months); co-infections with several NIRV, respiratory syncytial viruses, human metapneumoviruses and picornaviruses contributed most (33.1, 13.6, 15.8 and 18.2/100,000 person-months, respectively).ConclusionEarly testing for NIRV could be beneficial to clinical management of SARI patients, especially in children younger than 5 years, for whom the burden of NIRV-associated disease exceeds that of influenza.     

Estimating influenza outpatients' and inpatients' incidences from 2009 to 2011 in a tropical urban setting in the Philippines

Objectives

Although the public health significance of influenza in regions with a temperate climate has been widely recognized, information on influenza burden in tropical countries, including the Philippines, remains limited. We aimed to estimate influenza incidence rates for both outpatients and inpatients then characterized their demographic features.

Design

An enhanced surveillance was performed from January 2009 to December 2011 in an urbanized highland city. The influenza-like illness (ILI) surveillance involved all city health centers and an outpatient department of a tertiary government hospital. The severe acute respiratory infection (sARI) surveillance was also conducted with one government and four private hospitals since April 2009. Nasal and/or oropharyngeal swabs were collected and tested for influenza A, influenza B, and respiratory syncytial virus.

Results and Conclusions

We obtained 5915 specimens from 13 002 ILI cases and 2656 specimens from 10 726 sARI cases throughout the study period. We observed year-round influenza activity with two possible peaks each year. The overall influenza detection rate was 23% in the ILI surveillance and 9% in the sARI surveillance. The mean annual outpatient incidence rate of influenza was 5·4 per 1000 individuals [95% confidence interval (CI), 1·83–12·7], and the mean annual incidence of influenza-associated sARI was 1·0 per 1000 individuals (95% CI, 0·03–5·57). The highest incidence rates were observed among children aged <5 years, particularly those aged 6–23 months. Influenza posed a certain disease burden among inpatients and outpatients, particularly children aged <5 years, in an urbanized tropical city of the Philippines.     

Incidence,circulation, and spatiotemporal analysis of seasonal influenza in Shandong,China, 2008–2019: A retrospective study

BackgroundUnderstanding the influenza‐like illness (ILI) incidence, circulation pattern of virus strains and spatiotemporal pattern of influenza transmission are important for designing control interventions. Based on the 10 years'' surveillance data, we aimed to provide a baseline characterization and the epidemiology and dynamics of influenza virus in Shandong.MethodsWe extracted surveillance and laboratory testing data. We estimated the ILI incidence and analyzed the predominant virus. A wavelet power analysis was used to illustrate the periodicity. In addition, we applied a linear regression model to characterize the correlation of influenza seasonality with longitude.ResultsThe average ILI incidence was estimated to be 3744.79 per 1 million (95% confidence interval [CI]: 2558.09–4931.45) during 2009–2018. Influenza A/H1N1 and A/H3N2 strains predominated in the most influenza seasons in Shandong. The annual amplitude of influenza epidemics decreased with longitude (P < 0.05). In contrast, the epidemic peak of influenza emerged earlier in the western region and increased with longitude in influenza A (P < 0.05). The annual peak of the influenza B epidemic lagged a median of 4.2 weeks compared with that of influenza A.ConclusionsThe development or modification of seasonal influenza vaccination strategies requires the recognition that the incidence is higher in preschool‐ and school‐aged children. Although seasonal influenza circulates annually in Shandong, the predominant virus strain circulation pattern is extremely unpredictable and strengthening surveillance for the predominant virus strain is necessary. Lower longitude inland regions need to take nonpharmaceutical or pharmaceutical interventions in advance during influenza high‐occurrence seasons.     

Absence of cross-reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months-9 years: a prospective study

Please cite this paper as: McVernon et al. (2010) Absence of cross‐reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months–9 years: a prospective study. Influenza and Other Respiratory Viruses 5(1), 7–11. Background Early outbreaks of the pandemic influenza A (H1N1) 2009 virus predominantly involved young children, who fuelled transmission through spread in homes and schools. Seroprevalence studies conducted on stored serum collections indicated low levels of antibody to the novel strain in this age group, leading many to recommend priority immunisation of paediatric populations. Objectives In a prospective study, we sought evidence of cross‐reactive antibodies to the pandemic virus in children who were naïve to seasonal influenza vaccines, at baseline and following two doses of the 2009 Southern Hemisphere trivalent influenza vaccine (TIV). Patients/Methods Twenty children were recruited, with a median age of 4 years (interquartile range 3–5 years); all received two age appropriate doses of TIV. Paired sera were collected pre‐ and post‐vaccination for the assessment of vaccine immunogenicity, using haemagglutination inhibition and microneutralisation assays against vaccine‐related viruses and influenza A (H1N1) 2009. Results Robust responses to H3N2 were observed regardless of age or pre‐vaccination titre, with 100% seroconversion. Fewer seroconverted to the seasonal H1N1 component. Only two children were weakly seropositive (HI titre 40) to the pandemic H1N1 strain at study entry, and none showed evidence of seroconversion by HI assay following TIV administration. Conclusions Administration of 2009 Southern Hemisphere TIV did little to elicit cross‐reactive antibodies to the pandemic H1N1 virus in children, in keeping with assay results on stored sera from studies of previous seasonal vaccines. Our findings support the recommendations for influenza A (H1N1) 2009 vaccination of children in preparation for the 2010 winter season.     

Multisite virological influenza surveillance in India: 2004-2008

Please cite this paper as: Chadha et al. (2011) Multi site Virological Influenza Surveillance in India: 2004–2008. Influenza and Other Respiratory Viruses 6(3), 196–203. Background Influenza surveillance is important to identify circulating, emerging/reemerging strains and unusual epidemiological trends. With these objectives, a multisite human influenza surveillance network was initiated in India in 2004. Methods Epidemiologic data and throat swabs for laboratory testing were collected from patients with influenza‐like illness (ILI) and severe acute respiratory infections (SARI). Virus isolation was carried out in Madin–Darby canine kidney cells and strains identified by hemagglutination inhibition assay. Meteorological data were collected. Results From September 2004 to December 2008, 617 (4·43%) of 13928 cases yielded isolates: 27·8% were influenza A(H1N1), 29·8% were type A(H3N2), and 42·3% were type B. The yearly type and subtype distribution varied significantly from site to site. Peak influenza activity was observed from June to August in Delhi, Pune, and Kolkata and October to December in Chennai. Maximum influenza activity was seen during the rains in Delhi, Pune, Chennai, and Kolkata in correlation with virus isolations. Multivariate analysis of ILI cases showed chill/rigors, cough, fatigue, and ILI in family, correlated positively with isolation. Genetic analysis of Indian isolates revealed that viruses matched with vaccine strains by and large. Overlapping between circulating and vaccine component strains of consecutive years was also observed. Conclusions Seasonal influenza A(H1N1), H3N2, and type B co‐circulated in all regions without any particular pattern of movement of any subtype. Year‐round limited influenza activity with peaks during rains was observed. Genetic drifts and varying seasonality in different parts of the country suggest that a staggered timing of vaccination may be appropriate for India.     

Influenza and other respiratory viruses in three Central American countries

Please cite this paper as: Laguna‐Torres et al. (2011) Influenza and other respiratory viruses in three Central American countries. Influenza and Other Respiratory Viruses 5(2), 123–134. Background Despite the disease burden imposed by respiratory diseases on children in Central America, there is a paucity of data describing the etiologic agents of the disease. Aims To analyze viral etiologic agents associated with influenza‐like illness (ILI) in participants reporting to one outpatient health center, one pediatric hospital, and three general hospitals in El Salvador, Honduras, and Nicaragua Material & Methods Between August 2006 and April 2009, pharyngeal swabs were collected from outpatients and inpatients. Patient specimens were inoculated onto cultured cell monolayers, and viral antigens were detected by indirect and direct immunofluorescence staining. Results A total of 1,756 patients were enrolled, of whom 1,195 (68.3%) were under the age of 5; and 183 (10.4%) required hospitalization. One or more viral agents were identified in 434 (24.7%) cases, of which 17 (3.9%) were dual infections. The most common viruses isolated were influenza A virus (130; 7.4% of cases), respiratory syncytial virus (122; 6.9%), adenoviruses (63; 3.6%), parainfluenza viruses (57; 3.2%), influenza B virus (47; 2.7% of cases), and herpes simplex virus 1 (22; 1.3%). In addition, human metapneumovirus and enteroviruses (coxsackie and echovirus) were isolated from patient specimens. Discussion When compared to the rest of the population, viruses were isolated from a significantly higher percentage of patients age 5 or younger. The prevalence of influenza A virus or influenza B virus infections was similar between the younger and older age groups. RSV was the most commonly detected pathogen in infants age 5 and younger and was significantly associated with pneumonia (p < 0.0001) and hospitalization (p < 0.0001). Conclusion Genetic analysis of influenza isolates identified A (H3N2), A (H1N1), and B viruses. It also showed that the mutation H274Y conferring resistance to oseltamivir was first detected in Honduran influenza A/H1N1 strains at the beginning of 2008. These data demonstrate that a diverse range of respiratory pathogens are associated with ILI in Honduras, El Salvador, and Nicaragua. RSV infection in particular appears to be associated with severe disease in infants in the region.     

Now and future influenza vaccines

Influenza is a modern day plague. In the young, the clinical picture is classical, but in the elderly, the disease may go unsuspected until complications such as pneumonia develop. Influenza A and B viruses are responsible, and these viruses mutate with great regularity. Antibodies to the HA and NA surface antigens of influenza viruses, both naturally and vaccine induced, are protective. The earliest influenza vaccines were crude, toxic, and ineffective. With modern purification techniques, the egg-grown viruses have been turned into safe, immunogenic, and effective killed-virus vaccines--whole virus and split virus. Surveillance permits the correct virus strains to be incorporated into each new vaccine. Those who have been experiencing the worst effects of influenza have been identified. These individuals need to be immunized each year. In the future, live influenza virus vaccines may offer the benefits of ease of administration and longer-lasting protection. Synthetic peptides, genetically engineered antigens, and even nonantigen (anti-idiotype) vaccines are possible, but such vaccines will require adjuvant enhancement. For the present, greater efforts must be made to use existing influenza vaccines.