Annual Respiratory Syncytial Virus Research Articles

Variability in the Timing of Respiratory Syncytial Virus Epidemics in Guatemala, 2008-2018.

The description of local seasonality patterns in respiratory syncytial virus (RSV) incidence is important to guide the timing of administration of RSV immunization products. We characterized RSV seasonality in Guatemala using the moving epidemic method (MEM) with absolute counts of RSV-associated acute respiratory infections (ARI) from hospital surveillance in Santa Rosa and Quetzaltenango departments of Guatemala. From Week 17 of 2008 through Week 16 of 2018, 8487 ARI cases tested positive for RSV by rRT-PCR. Season onsets varied up to 5 months; early seasons starting in late May to early August and finishing in September to November were most common, but late seasons starting in October to November and finishing in March to April were also observed. Both epidemic patterns had similar durations ranging from 4 to 6 months. Epidemic thresholds (the levels of virus activity that signal the onset and end of a seasonal epidemic) calculated prospectively using previous seasons' data captured between 70% and 99% of annual RSV detections. Onset weeks differed by 2-10 weeks, and offset weeks differed by 2-16 weeks between the two surveillance sites. Variability in the timing of seasonal RSV epidemics in Guatemala demonstrates the difficulty in precisely predicting the timing of seasonal RSV epidemics based on onset weeks from past seasons and suggests that maximal reduction in RSV disease burden would be achieved through year-round vaccination and immunoprophylaxis administration to at-risk infants.

Estimating the Undetected Burden of Respiratory Syncytial Virus Hospitalizations in Adults Through Capture-Recapture Methods.

Traditional surveillance systems may underestimate the burden caused by respiratory syncytial virus (RSV). Capture-recapture methods provide alternatives for estimating the number of RSV-related hospitalizations in a population. Capture-recapture methods were used to estimate the number of RSV-related hospitalizations in adults in Middle Tennessee from two independent hospitalization surveillance systems during consecutive respiratory seasons from 2016-2017 to 2019-2020. Data from the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and the Emerging Infections Program (EIP) were used. Annual RSV hospitalization rates were calculated using the capture-recapture estimates weighted by hospitals' market share divided by the corresponding census population. Using capture-recapture methods, the estimated overall adult hospitalization rates varied from 8.3 (95% CI: 5.9-15.4) RSV-related hospitalizations per 10,000 persons during the 2016-2017 season to 28.4 (95% CI: 18.2-59.0) hospitalizations per 10,000 persons in the 2019-2020 season. The proportion of hospitalizations that HAIVEN determined ranged from 8.7% to 36.7% of the total capture-recapture estimated hospitalization, whereas EIP detected 23.5% to 52.7% of the total capture-recapture estimated hospitalizations. Capture-recapture estimates showed that individual traditional surveillance systems underestimated the hospitalization burden in adults. Using capture-recapture allows for a more comprehensive estimate of RSV hospitalizations.

Epidemiology and Disease Burden of Respiratory Syncytial Virus Infection in Adults.

Respiratory syncytial virus (RSV) constitutes a significant cause of respiratory illness and mortality among older adults, a demographic that is expanding with considerable impact on healthcare systems worldwide. The actual burden of RSV in this population may still be underestimated, owing to factors such as low awareness and suboptimal diagnostic sensitivity in adults, the lack of robust RSV surveillance systems, and the infrequent use of diagnostic testing. Recent advancements in respiratory virus detection have spurred further exploration into appropriate preventive and therapeutic strategies. The recent approval of two vaccines highlights the critical need for the precise estimation of the RSV disease burden to optimize the effectiveness and cost-efficiency of immunization programs. This narrative review aimed to summarize the existing knowledge of the RSV burden in adults with a particular focus on older adults, incorporating data from Korea. Overall, current estimates indicate that the annual RSV attack rate in the general adult population ranges from 1 - 7%, increasing to approximately 4 - 10% among elderly and high-risk groups. The in-hospital mortality rate can be estimated to be around 7 - 10%, rising up to 40% among intensive care unit-admitted patients. To elucidate RSV's disease burden, further continuing research, including population-based studies, is necessary.

The Annual Economic Burden of Respiratory Syncytial Virus in Adults in the United States.

Current estimates of the economic burden of respiratory syncytial virus (RSV) are needed for policymakers to evaluate adult RSV vaccination strategies. A cost-of-illness model was developed to estimate the annual societal burden of RSV in US adults aged ≥60 years. Additional analyses were conducted to estimate the burden of hospitalized RSV in all adults aged 50-59 years and in adults aged 18-49 years with potential RSV risk factors. Among US adults aged ≥60 years, the model estimated 4.0 million annual RSV cases (95% uncertainty interval [UI], 2.7-5.6 million) and an annual economic burden of $6.6 billion (95% UI, $3.1-$12.9 billion; direct medical costs, $2.9 billion; indirect costs, $3.7 billion). The 4% of RSV cases that were hospitalized contributed to 94% of direct medical costs. Additional analyses estimated $422 million in annual hospitalization costs among all adults aged 50-59 years. Among adults aged 18-49 years with RSV risk factors, annual per capita burden was highest among people with congestive heart failure at $51 100 per 1000 people. The economic burden of RSV is substantial among adults aged ≥50 years and among adults aged 18-49 years with RSV risk factors, underscoring the need for preventive interventions for these populations.

Respiratory syncytial virus reinfections among infants and young children in the United States, 2011-2019.

Although respiratory syncytial virus (RSV) immunoprophylaxis is recommended for high-risk infants, the American Academy of Pediatrics (AAP) recommends against immunoprophylaxis in the same season following a breakthrough hospitalization due to limited risk for a second hospitalization. Evidence in support of this recommendation is limited. We estimated population-based re-infection rates from 2011-2019 in children <5 years since RSV risk remains relatively high in this age group. Using claims data from private insurance enrollees, we established cohorts of children <5 years who were followed to ascertain annual (July 1-June 30) and seasonal (November 1- February 28/29) RSV recurrence estimates. Unique RSV episodes included inpatient encounters with RSV diagnosis ≥30 days apart, and outpatient encounters ≥30 days apart from each other as well as from inpatient encounters. The risk of annual and seasonal re-infection was calculated as the proportion of children with a subsequent RSV episode in the same RSV year/season. Over the 8 assessed seasons/years (N = 6,705,979) and across all age groups annual inpatient and outpatient infection rates were 0.14% and 1.29%, respectively. Among children with a first infection, annual inpatient and outpatient re-infection rates were 0.25% (95% confidence interval (CI) = 0.22-0.28) and 3.44% (95% CI = 3.33-3.56), respectively. Both infection and re-infection rates declined with age. While medically-attended re-infections contributed numerically only a fraction of the total RSV infections, re-infections among those with previous infection in the same season were of similar magnitude as the general infection risk, suggesting that a previous infection may not attenuate the risk for a re-infection.

Intranasal and intrapulmonary vaccination with an M protein-deficient respiratory syncytial virus (RSV) vaccine improves clinical signs and reduces viral replication in infant baboons after an RSV challenge infection

Respiratory syncytial virus (RSV) is the major viral respiratory pathogen for human infants and children. Despite a severe global burden incurred by annual RSV epidemics, there is no licensed RSV vaccine. We have developed an RSV vaccine from a human RSV strain from which the gene for the viral M protein has been deleted (“Mnull RSV”). RSV infects airway cells and produces each of its proteins. The M protein is responsible for reassembling the various other synthesized viral proteins into new, intact virus. In the absence of the M protein, therefore, reassembly does not occur, and the Mnull RSV does not replicate.We vaccinated 2-week old infant baboons with Mnull RSV either intranasally (IN) or directly into the lung (intratracheal, or IT), then infected these animals by inoculating human RSV directly into the lung. IN vaccination induced inconsistent serum RSV neutralizing antibody (NA) responses, but provided moderate reductions in respiratory rates, overall signs of illness and viral replication in bronchoalveolar lavage (BAL) fluid following infection. Intratracheal vaccination induced much stronger RSV NA responses, which persisted for at least 4–6 months. Following RSV infection, animals vaccinated by the IT route had much greater reductions in tachypnea and work of breathing than animals vaccinated IN, and had undetectable amounts of virus in BAL fluids. These results support the further development of IT Mnull RSV vaccination to reduce the impact of RSV infection in humans.

1526. The economic impact of respiratory syncytial virus (RSV) in infants in the United States: systematic literature review

BackgroundRespiratory syncytial virus (RSV) is a human orthopneumovirus spread by direct contact with symptomatic, infected individuals. An estimated 587,000 RSV LRTIs result in inpatient or outpatient encounters annually among US infants (Rainisch et al 2019). The health care costs associated with RSV include medical costs to insurers, governments, and households, travel, and loss of wages.Initial summary of Inpatient and Ambulatory Medical Costs p Infant w RSV.JPG Jun 17th, 2020 @ 2:44 PM 852 x 572 122.3 Kb MethodsA systematic literature review of the costs associated with children who have RSV was conducted. Following PRISMA methodology, key search terms were searched within article titles and abstracts through PubMed, EconLit, and Scopus. A total of 1,942 unique abstracts were screened independently by two authors and reduced to 180 articles after applying inclusion and exclusion criteria. The number of included articles after reviewing the full text was 66. Costing results were adjusted to USD2020 based on the Medical Care Consumer Price Index.ResultsCosting results were reported mainly for medical costs in inpatient settings. Initial results show that annual mean inpatient costs per RSV patient range among individual studies from $9,825 (SD=$25,227) for full term infants to $26,120 (SD unspecified) for late preterm infants (Table 1). Costing results vary by gestational age, with late preterm infants having an annual mean inpatient cost almost 1.6 times that of a full term infant. Inpatient costs for RSV infants are higher for commercial pay versus Medicaid, for both full term infants (commercial mean=$16,489 SD=$31,068, Medicaid mean=$10,291 SD=$64,625) and late preterm infants (commercial mean=$23,836; SD=$43,709, Medicaid mean=$18,864 SD=$28,716). Annual RSV ambulatory costs per infant vary between $4,371 (SD=$13,411) and $19,963 (SD=$27,269), depending on gestational age. Other relevant RSV costs include preventative drug costs, such as palivizumab (average $11,954 per infant).ConclusionThe literature describes the economic impact of RSV primarily for hospitalization of children with underlying comorbidities. There is a need to better understand costing results for RSV, including the burden in ambulatory settings and indirect costs to families affected.Disclosures All Authors: No reported disclosures

Respiratory syncytial virus infection trend is associated with meteorological factors

Respiratory syncytial virus (RSV) infects young children and causes influenza-like illness. RSV circulation and prevalence differ among countries and climates. To better understand whether climate factors influence the seasonality of RSV in Thailand, we examined RSV data from children ≤ 5 years-old who presented with respiratory symptoms from January 2012–December 2018. From a total of 8,209 nasopharyngeal samples, 13.2% (1,082/8,209) was RSV-positive, of which 37.5% (406/1,082) were RSV-A and 36.4% (394/1,082) were RSV-B. The annual unimodal RSV activity from July–November overlaps with the rainy season. Association between meteorological data including monthly average temperature, relative humidity, rainfall, and wind speed for central Thailand and the incidence of RSV over 7-years was analyzed using Spearman’s rank and partial correlation. Multivariate time-series analysis with an autoregressive integrated moving average (ARIMA) model showed that RSV activity correlated positively with rainfall (r = 0.41) and relative humidity (r = 0.25), but negatively with mean temperature (r = − 0.27). The best-fitting ARIMA (1,0,0)(2,1,0)12 model suggests that peak RSV activity lags the hottest month of the year by 4 months. Our results enable possible prediction of RSV activity based on the climate and could help to anticipate the yearly upsurge of RSV in this region.

Meteorological factors affecting respiratory syncytial virus infection: A time-series analysis.

Respiratory syncytial virus (RSV) infection is a major cause of hospitalization in children. Meteorological factors are known to influence seasonal RSV epidemics, but the relationship between meteorological factors and RSV infection in children is not well understood. We aimed to explore the relationship between meteorological factors and RSV infections among hospitalized children, using different statistical models. We conducted a retrospective review concerning children with RSV infections admitted to a tertiary pediatric hospital in Wenzhou, China, between January 2008 and December 2017. The relationship between meteorological factors (average daily temperatures, average daily relative humidity, rainfall, rainfall days, and wind speed) and the incidence of RSV in hospitalized children was analyzed using three time-series models, namely an autoregressive integrated moving average (ARIMA) model, a generalized additive model (GAM), and a least absolute shrinkage and selection operator (LASSO)-based model. In total, 15 858 (17.6%) children tested positive for RSV infection. The ARIMA model revealed a marked seasonal pattern in the RSV detection rate, which peaked in winter and spring. The model was a good predictor of RSV incidence (R2 : 83.5%). The GAM revealed that a lower temperature and higher wind speed preceded increases in RSV detection. The LASSO-based model revealed that temperature and relative humidity were negatively correlated with RSV detection. Seasonality of RSV infection in hospitalized children correlated strongly with temperature. The LASSO-based model can be used to predict annual RSV epidemics using weather forecast data.

Utilidad de la vigilancia microbiológica del virus respiratorio sincitial en Galicia (España): 2008-2017

ObjectiveTo describe whether the microbiological information of the respiratory syncytial virus (RSV), provided by four hospitals on a weekly basis, adequately captures the seasonality of the RSV in the entire community. MethodRetrospective descriptive study. We compared the detection of RSV in respiratory samples of patients (hospitalized and not) from all age groups, from the 4 hospitals that are part of the microbiological surveillance system (MSS), with data from the Minimum Basic Data Set of hospitalization for bronchiolitis by RSV or another infectious organism, in patients under 5 years of age, admitted to any public hospital in Galicia (seasons 2008/2009 to 2016/2017). An epidemic wave period was considered when the positivity of RSV detections in the total respiratory samples of the SVM exceeded 10%. The sensitivity of the MSS was calculated as a percentage of admissions occurring in the epidemic wave. ResultsMSS sensitivity was 92% (86%-96%) for RSV bronchiolitis admissions in each season and 79% (75%-84%) for total bronchiolitis admissions. ConclusionsThe RSV microbiological surveillance system, based on data from only 4 hospitals, showed very good sensitivity to predict the start and end of the annual RSV wave throughout the Galician region. These results support the use of this information to alert the entire health system of the onset of the wave.

Respiratory Syncytial Virus Surveillance System in Japan: Assessment of Recent Trends, 2008-2015.

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract illness in infants and young children. In Japan, surveillance for RSV infection started in 2003 based on approximately 3,000 pediatric sentinel sites. In recent years, RSV notifications have increased, but the interpretation of trends has been challenging due to a suspected increase in testing frequency and the expansion of the insurance coverage for RSV testing to include certain outpatients in late 2011. Therefore, we evaluated RSV surveillance data during 2008-2015, considering the number of sites that reported at least one RSV case during a surveillance year and restricting to sites that had continuous reporting status since 2008. While annual RSV notifications had increased, the number of sites reporting also increased. And the same magnitude of increase was not observed when the number of cases reported was restricted to the 1,372 sites that had continuous reporting status since 2008. Additionally, in the year following the insurance expansion, RSV notifications increased more remarkably for clinics than for hospitals. These results suggested that some of the recent increases in notifications might be due to an increase in testing frequency.

On the Relative Role of Different Age Groups During Epidemics Associated With Respiratory Syncytial Virus.

While circulation of respiratory syncytial virus (RSV) results in high rates of hospitalization, particularly among young children and elderly individuals, little is known about the role of different age groups in propagating annual RSV epidemics. We evaluate the roles played by individuals in different age groups during RSV epidemics in the United States between 2001 and 2012, using the previously defined relative risk (RR) statistic estimated from the hospitalization data from the Healthcare Cost and Utilization Project. Transmission modeling was used to examine the robustness of our inference method. Children aged 3-4 years and 5-6 years each had the highest RR estimate for 5 of 11 seasons included in this study, with RSV hospitalization rates in infants being generally higher during seasons when children aged 5-6 years had the highest RR estimate. Children aged 2 years had the highest RR estimate during one season. RR estimates in infants and individuals aged ≥11 years were mostly lower than in children aged 1-10 years. Highest RR values aligned with groups for which vaccination had the largest impact on epidemic dynamics in most model simulations. Our estimates suggest the prominent relative roles of children aged ≤10 years (particularly among those aged 3-6 years) in propagating RSV epidemics. These results, combined with further modeling work, should help inform RSV vaccination policies.

Clinical and Socioeconomic Burden of Respiratory Syncytial Virus Infection in Children.

Vaccines and antivirals against respiratory syncytial virus (RSV) are being developed, but there are scarce data on the full impact of RSV infection on outpatient children. We analyzed the burden of RSV illness in a prospective cohort study of children aged ≤13 years during 2 consecutive respiratory seasons in Turku, Finland (2231 child-seasons of follow-up). We examined the children and obtained nasal swabs for the detection of RSV during each respiratory illness. The parents filled out daily symptom diaries throughout the study. Of 6001 medically attended respiratory infections, 302 (5%) were caused by RSV. Per 1000 children, the average annual RSV infection incidence rates among children aged <3, 3-6, and 7-13 years were 275, 117, and 46 cases, respectively. In children aged <3 years, acute otitis media developed in 58%, and 66% of children in this age group received antibiotics. The mean duration of RSV illness was longest (13.0 days) and the rate of parental work absenteeism was highest (136 days per 100 children with RSV illness) in children aged <3 years. The burden of RSV is particularly great among outpatient children aged <3 years. Young children are an important target group for the development of RSV vaccines and antivirals.

Trends in Respiratory Syncytial Virus and Bronchiolitis Hospitalization Rates in High-Risk Infants in a United States Nationally Representative Database, 1997-2012.

BackgroundRespiratory syncytial virus (RSV) causes significant pediatric morbidity and is the most common cause of bronchiolitis. Bronchiolitis hospitalizations declined among US infants from 2000‒2009; however, rates in infants at high risk for RSV have not been described. This study examined RSV and unspecified bronchiolitis (UB) hospitalization rates from 1997‒2012 among US high-risk infants.MethodsThe Kids’ Inpatient Database (KID) infant annual RSV (ICD-9 079.6, 466.11, 480.1) and UB (ICD-9 466.19, 466.1) hospitalization rates were estimated using weighted counts. Denominators were based on birth hospitalizations with conditions associated with high-risk for RSV: chronic perinatal respiratory disease (chronic lung disease [CLD]); congenital airway anomalies (CAA); congenital heart disease (CHD); Down syndrome (DS); and other genetic, metabolic, musculoskeletal, and immunodeficiency conditions. Preterm infants could not be identified. Hospitalizations were characterized by mechanical ventilation, inpatient mortality, length of stay, and total cost (2015$). Poisson and linear regression were used to test statistical significance of trends.ResultsRSV and UB hospitalization rates were substantially elevated for infants with higher-risk CHD, CLD, CAA and DS without CHD compared with all infants. RSV rates declined by 47.0% in CLD and 49.7% in higher-risk CHD infants; no other declines in high-risk groups were observed. UB rates increased in all high-risk groups except for a 22.5% decrease among higher-risk CHD. Among high-risk infants, mechanical ventilation increased through 2012 to 20.4% and 13.5% of RSV and UB hospitalizations; geometric mean cost increased to $31,742 and $25,962, respectively, and RSV mortality declined to 0.9%.ConclusionsAmong high-risk infants between 1997 and 2012, RSV hospitalization rates declined among CLD and higher-risk CHD infants, coincident with widespread RSV immunoprophylaxis use in these populations. UB hospitalization rates increased in all high-risk groups except higher-risk CHD, suggesting improvement in the health status of higher-risk CHD infants, potentially due to enhanced surgical interventions. Mechanical ventilation use and RSV and UB hospitalization costs increased while RSV mortality declined.

Seasonality of respiratory syncytial virus in Buenos Aires. Relationship with global climate change.

Global climate change circulation pattern respiratory syncytial virus (RSV). We assessed whether RSV season has changed over the past 20 years and its correlation with mean annual temperature. Cross-sectional study that included records of RSV and temperatures from Buenos Aires (1995-2014). RSV season onset, offset and duration, and its correlation with mean annual temperature were described for each year. A total of 8109 RSV infections were identified. The duration of RSV season reduced significantly (1995: 29 weeks vs. 2014: 17 weeks; R: 0.6; p < 0.001) due to an early ending (1995: week 45 vs. 2014: week 33; R: 0.6; p < 0.001). No correlation was observed between mean annual temperature and RSV season start, end and duration. Over the past 20 years, RSV season shortened significantly, but no correlation with temperature was observed.

Estimating the hospitalization burden associated with influenza and respiratory syncytial virus in New York City, 2003-2011.

BackgroundHospitalization burden associated with influenza and respiratory syncytial virus (RSV) is uncertain due to ambiguity in the inference methodologies employed for its estimation.ObjectivesUtilization of a new method to quantitate the above burden.MethodsWeekly hospitalization rates for several principal diagnoses from 2003 to 2011 in New York City by age group were regressed linearly against incidence proxies for the major influenza subtypes and RSV adjusting for temporal trends and seasonal baselines.ResultsAverage annual rates of influenza-associated respiratory hospitalizations per 100 000 were estimated to be 129 [95% CI (79, 179)] for age <1, 36·3 (21·6, 51·4) for ages 1–4, 10·6 (7·5, 13·7) for ages 5–17, 25·6 (21·3, 29·8) for ages 18–49, 65·5 (54·0, 76·9) for ages 50–64, 125 (105, 147) for ages 65–74, and 288 (244, 331) for ages ≥75. Additionally, influenza had a significant contribution to hospitalization rates with a principal diagnosis of septicemia for ages 5–17 [0·76 (0·1, 1·4)], 18–49 [1·02 (0·3, 1·7)], 50–64 [4·0 (1·7, 6·3)], 65–74 [8·8 (2·2, 15·6)], and ≥75 [38·7 (25·7, 52·9)]. RSV had a significant contribution to the rates of respiratory hospitalizations for age <1 [1900 (1740, 2060)], ages 1–4 [117 (70, 167)], and ≥75 [175 (44, 312)] [including chronic lower respiratory disease, 90 (43, 140)] as well as pneumonia & influenza hospitalizations for ages 18–49 [6·2 (1·1, 11·3)] and circulatory hospitalizations for ages ≥75 [199 (13, 375)].ConclusionsThe high burden of RSV hospitalizations among young children and seniors age ≥75 suggests the need for additional control measures such as vaccination to mitigate the impact of annual RSV epidemics. Our estimates for influenza-associated hospitalizations provide further evidence of the burden of morbidity associated with influenza, supporting current guidelines regarding influenza vaccination and antiviral treatment.

Modelling the seasonal epidemics of respiratory syncytial virus in young children.

BackgroundRespiratory syncytial virus (RSV) is a major cause of paediatric morbidity. Mathematical models can be used to characterise annual RSV seasonal epidemics and are a valuable tool to assess the impact of future vaccines.ObjectivesConstruct a mathematical model of seasonal epidemics of RSV and by fitting to a population-level RSV dataset, obtain a better understanding of RSV transmission dynamics.MethodsWe obtained an extensive dataset of weekly RSV testing data in children aged less than 2 years, 2000–2005, for a birth cohort of 245,249 children through linkage of laboratory and birth record datasets. We constructed a seasonally forced compartmental age-structured Susceptible-Exposed-Infectious-Recovered-Susceptible (SEIRS) mathematical model to fit to the seasonal curves of positive RSV detections using the Nelder-Mead method.ResultsFrom 15,830 specimens, 3,394 were positive for RSV. RSV detections exhibited a distinct biennial seasonal pattern with alternating sized peaks in winter months. Our SEIRS model accurately mimicked the observed data with alternating sized peaks using disease parameter values that remained constant across the 6 years of data. Variations in the duration of immunity and recovery periods were explored. The best fit to the data minimising the residual sum of errors was a model using estimates based on previous models in the literature for the infectious period and a slightly lower estimate for the immunity period.ConclusionsOur age-structured model based on routinely collected population laboratory data accurately captures the observed seasonal epidemic curves. The compartmental SEIRS model, based on several assumptions, now provides a validated base model. Ranges for the disease parameters in the model that could replicate the patterns in the data were identified. Areas for future model developments include fitting climatic variables to the seasonal parameter, allowing parameters to vary according to age and implementing a newborn vaccination program to predict the effect on RSV incidence.

Respiratory Syncytial Virus Surveillance in the United States, 2007–2012

Background:Annual respiratory syncytial virus (RSV) outbreaks throughout the US exhibit variable patterns in onset, peak month of activity and duration of season. RSVAlert®, a US surveillance system, collects and characterizes RSV test data at national, regional, state and local levels.Methods:RSV test data from 296 to 666 laboratories from 50 states, the District of Columbia and Puerto Rico (as of 2010) were collected during the 2007–2008 to 2011–2012 RSV seasons. Data were collected in early August/September to the following August/September each season. Participating laboratories provided the total number and types of RSV tests performed each week and test results. RSV season onset and offset were defined as the first and last, respectively, of 2 consecutive weeks during which the mean percentage of specimens testing positive for RSV was ≥10%.Results:Nationally, the RSV season onset occurred in October/November of each year with offset occurring in March/April of the following year. The RSV season averaged 20 weeks and typically occurred earliest in the South and latest in the West. The onset, offset and duration varied considerably within the US Department of Health and Human Services regions. RSV activity in Puerto Rico was elevated throughout the 2-year period studied. Median onset in core-based statistical areas ranged from 2 weeks earlier to 5 weeks later than those in their corresponding states.Conclusions:Substantial variability existed in the timing of RSV activity at all geographic strata analyzed. RSV actively circulated (ie, ≥10%) in many areas outside the traditionally defined RSV epidemic period of November to March.

Hospitalizations for Acute Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Thailand, 2008-2011

Few population-based estimates of the incidence of respiratory syncytial virus (RSV) infection in low- or middle-income countries are available. We describe the incidence and epidemiology of hospitalizations for RSV-associated acute lower respiratory tract infection (ALRI) detected by active population-based surveillance in 2 rural Thailand provinces during 2008-2011. Patients hospitalized with ALRI were systematically sampled. Consenting patients provided nasopharyngeal swab specimens for RSV testing by real-time reverse-transcription polymerase chain reaction. Of 13 982 enrolled patients hospitalized with ALRI, 1137 (8.1%) were RSV positive. After adjustment for sampling and nonenrollment, the incidence of RSV-associated ALRI hospitalization was 85 cases per 100,000 persons/year. The highest rates occurred among children aged <5 years (981 cases per 100,000 persons/year) and <1 year (1543 cases per 100,000 persons/year). Rates were low among older children and young adults but high among persons aged >65 years (130 cases per 100,000 persons/year). Eight (0.7%) RSV-infected study patients died during hospitalization. Annual RSV hospitalizations peaked during July-October with almost no documented RSV hospitalizations during January-June. Our findings demonstrate the substantial contribution of RSV to global ALRI burden, especially in children aged <5 years and the elderly, and underscore the urgent need for effective prevention measures.

Molecular Characterization of a Respiratory Syncytial Virus Outbreak in a Hematology Unit in Heidelberg, Germany

In 2011 and 2012, a large outbreak of respiratory syncytial virus (RSV) infections affecting 57 laboratory-confirmed patients occurred in an adult hematology unit in Heidelberg, Germany. During the outbreak investigation, we performed molecular genotyping of RSV strains to differentiate between single versus multiple introductions of the virus into the unit. Furthermore, we assessed the time of viral shedding of consecutive samples from the patients in order to better understand the possible impact of prolonged shedding for outbreak control management. We used subtype-specific reverse transcription-PCR on nasopharyngeal and bronchoalveolar specimens for routine diagnostics and for measuring the viral shedding period. Samples of 47 RSV-infected patients involved in the outbreak were genotyped by sequence analysis and compared to samples from RSV-infected hospitalized children representing the timing of the annual RSV epidemic in the community. Molecular investigation of the virus strains from clinical samples revealed a unique cluster with identical nucleotide sequences of RSV type A (RSV A outbreak strain) for 41 patients, while 3 patients were infected with different RSV A (nonoutbreak) strains and three other patients with RSV type B. Outbreak strains were identified in samples from November 2011 until January 2012, while nonoutbreak strains were from samples coinciding with the community epidemic in February and March 2012. Median duration of viral shedding time was 24.5 days (range, 1 to 168 days) with no difference between outbreak and nonoutbreak strains (P = 0.45). Our investigation suggests a single introduction of the RSV A outbreak strain into the unit that spread among the immunocompromised patients. Prolonged viral shedding may have contributed to nosocomial transmission and should be taken into account in the infection control management of RSV outbreaks in settings with heavily immunosuppressed patients.