DOI: 10.6084/m9.figshare.27917049.v1
title: Adult respiratory syncytial virus disease burden: systematic literature review in Africa, Asia, Latin America, and the Middle East (2012–2022)

description: <b>Aim:</b> To assess the burden of respiratory syncytial virus-associated disease in older adults (RSV OA), ≥50 years old, in World Health Organization region countries in Africa, the Americas (except for Canada and the USA), Eastern Mediterranean, Europe (except for European Union countries and the UK), South-East Asia, and Western Pacific (except for Australia, China, Japan, New Zealand, and South Korea). <b>Materials & methods:</b> English-language publications published and indexed in Embase (2012 to 29 September 2022) and MEDLINE (2012 to 29 September 2022) were reviewed. RSV OA outcomes of interest: epidemiology, testing/diagnostic methods, clinical/humanistic burden. <b>Results:</b> Nine RSV OA-burden statistics publications were identified from Africa (Kenya, Madagascar, and South Africa), the Americas (Guatemala), Eastern Mediterranean (Morocco), South-East Asia (Thailand), and Western Pacific (Hong Kong). One study described RSV hospital course (9-day median length of stay, 9.4% intensive-care admission rate), and seven studies reported case-fatality ratios (range, 7.5–15.9%). A third (3/9) of the studies investigated uniquely older adult disease. <b>Conclusion:</b> The limited details of RSV OA burden suggest nonetheless that RSV-associated hospitalization courses and mortality rates are substantial. While considerable surveillance needs remain, optimizing RSV vaccine access through immunization programs in these WHO region countries are essential steps to control RSV OA disease burden. This review article describes studies that were done between 2012 and 2022 about the serious illness caused by the respiratory syncytial virus (RSV) in older adult (OA) patients. We wanted to see what these studies said about how many adults tested positive (and how often the virus was identified), how long people infected by this virus stayed in the hospital, and how many died. We focused on countries that were not looked at in previous review articles to identify nine studies with information about RSV OA disease across five WHO regions in seven different countries – Guatemala, Hong Kong, Kenya, Madagascar, Morocco, Thailand, and South Africa. Only three of the nine studies gave us information specifically about older adults. One of these three studies showed that adults usually stayed in the hospital for about 9 days, and about 9% of them had to go to the intensive-care unit. Seven of the nine studies told us about how frequently hospitalized adults infected by the virus died, which was between 8 and 16%. This review tells us that more research is needed about how this virus affects older adults, especially in Africa, Asia, Latin America, and the Middle East. Although consequential for older adult (OA) populations, the respiratory syncytial virus (RSV) acute respiratory infection (ARI) burden is often underestimated, as compared with the well-established risk for neonates and young infants. The objective of this systematic literature review is to present a gap analysis of RSV OA disease-burden publications among countries within the six WHO regions where the epidemiology is not fully documented, while excluding from the review North America, Europe, and some countries of the Western Pacific that are already well represented in the international RSV OA disease-burden literature. This review included studies published between 2012 and 2022 investigating RSV outcomes of interest including epidemiology, testing/diagnostic methods, and clinical/humanistic burden. The entire systematic literature review included both children (0–5 years old) and adults; this current paper focused on publications from the adult population, particularly in older adults. Geographical range comprised countries classified within the six WHO regions: Africa, the Americas (except for Canada and the USA), Eastern Mediterranean, Europe (except for European Union countries and the UK), South-East Asia, and Western Pacific (except for Australia, China, Japan, New Zealand, and South Korea). RSV outcomes of interest included hospitalization course, mortality and case fatality, RSV-testing positivity rates, and incidence. This review revealed substantial gaps: RSV OA-burden evidence identified only nine published studies, 4.7% (7/149) of the countries of interest, and among these nine studies there were only three, from Thailand and Hong Kong, that reported uniquely adult estimates. Publications describing RSV OA hospitalization course showed a 9% intensive-care admission rate (one study) and a mortality/case fatality up to 15.9% (seven studies). RSV positivity rates varied between studies, likely due to patient factors such as age range, presence of comorbid conditions, respiratory infection case definitions, and sampling timing, as well as differences in sensitivity between the chosen laboratory tests. Our findings suggest that the research gaps in the RSV OA literature, although multifactorial, can be attributed mainly to insufficient/imprecise information and to biased information. RSV OA disease incidence values are confounded by underestimation due to inadequate case definitions that require presence of fever, incomplete testing (by use of lower sensitivity immunofluorescence assay testing and of single site specimen sampling), and insufficient surveillance by enrolling few adult patients. A better understanding of the burden of RSV OA disease across Africa, Asia, Latin America, and the Middle East can be accomplished in epidemiologic studies by initiation or enhancement of surveillance systems, improvement of RSV testing methods and sampling rates, and application of statistical modeling methods. The positive results from clinical trials have led to regulatory approvals of different RSV vaccines in several countries, presenting an opportunity to lower the OA disease burden across Africa, Asia, Latin America, and the Middle East in the near future through immunization. Standardizing RSV OA epidemiology methods (to establish hospitalization course, to determine mortality, to test positivity rate, and to establish incidence values) and tackling under-ascertainment of RSV OA disease burden (through enhanced RSV positivity testing and by applying statistical modeling) across the six WHO regions would enhance cross-study comparison analyses. Implementation of RSV OA vaccination strategies could potentially provide indirect protection, through control of carriage and transmission, while directly preventing RSV ARI in older adults.