Journal of Human Virology & Retrovirology Seasonality of Respiratory Syncytial Virus - Lower Respiratory Tract Infection (RSV-LRTI) in Children in Developing Countries Submit Manuscript | http://medcraveonline.com Introduction Lower respiratory tract infection (LRTI) is the leading global cause of death in children between 1 month and 5 years of age [1-4]. Clinical characteristics of RSV infection include upper respiratory infection with rhinorrhea and nasal congestion lasting between 7 and 12 days. Re-infection rates vary between 6% and 83% each year, showing that initial infection does not confer immunity to succeeding infection [5]. By the age of 2 years, nearly all children have had RSV infection [6]. More serious disease involving the lower respiratory tract may develop in older children especially in immunocompromised and cardiopulmonary disease patients [7,8]. RSV season varies over time and from location to location [9,10]. The start and end of RSV season can vary year to year, state to state, and can even vary within communities in the same region [9,11]. In countries with temperate climates, RSV causes epidemics of LRTI among infants and young children during late fall, winter, and early spring. In temperate climate regions, the RSV epidemic pattern depends on the temperature rather than the rainfall pattern. Most communities with temperate climates have a well- defined season of 3 to 5 months usually starting in the Northern hemisphere in October or November and continuing until February or March, followed by a peak in activity in the Southern hemisphere. In the southern hemisphere, wintertime epidemics occur from May to September. In addition, RSV studies conducted in temperate climates have identified a biannual pattern in the peak of RSV epidemics and RSV hospitalization rates, whereby the severity of RSV seasons alternates between milder and more severe. However, this is not predictable, and the differences may be more related to climatic changes [12]. This study aimed to systematically aggregate and analyze published epidemiological data on the seasonality of RSV lower respiratory tract infection in young children in developing countries (Table 1). Materials and Methods Potentially relevant published articles were identified through literature searches of the following bibliographic databases: PubMed, Web of knowledge, and Embase. To access publications from developing countries that might not be included in those databases, searches in SciELO, Indian MEDLARS, Bioline International, and African Journals online were also performed. The following combination of MesH terms (Medical Subject Heading terms) and individual search terms were used: (Respiratory Syncytial Viruses OR pneumonia OR bronchiolitis OR respiratory tract infections) AND (developing country OR each individual country of the developing countries) for the epidemiological review, and (Respiratory Syncytial Viruses AND vaccine) for the review of vaccine development updates. The searches were restricted to studies of human subjects that were published in English between 2002 and 2014. Manual searches of reference from potentially relevant articles were also performed to identify additional studies that may have been missed using the computer-assisted strategy. For the purpose of this review, the developing countries were defined as the ones designated as such by either World Bank (low, lower middle and upper middle- income countries) or World Health Organization. Countries with a contradiction of development status classification between World Bank and WHO were included within the developing countries group for this review. Volume 3 Issue 1 - 2016 1 University di Siena, Italy 2 Department of Pediatrics, Siriraj Hospital Mahidol University, Thailand 3 Novartis Vaccines and Diagnostics, Italy *Corresponding author: Sirintip Sricharoenchai, Department of Pediatrics, Siriraj Hospital Mahidol University, Pediatric Infectious Diseases Unit, 2 Prannok Road, Bangkok 10700, Thailand, Email: Received: December 27, 2015 | Published: January 11, 2016 Review Article J Hum Virol Retrovirol 2016, 3(1): 00076 Abstract Respiratory Syncytial Virus (RSV), an enveloped RNA virus with a non-segmented single-stranded negative-sense genome, is the primary cause of hospitalization in the first year of life for children in most parts of the world. The global estimate in 2005 indicated that at least 33.8 million episodes of RSV associated acute lower respiratory infection (ALRI) occurred worldwide in children younger than 5 years and most of these deaths occurred in developing countries. This study aimed to systematically aggregate and analyze published epidemiological data on the seasonality of RSV lower respiratory tract infections in young children in developing countries. Articles in English published between 2002 and 2014 were identified through literature searches in PubMed, Web of knowledge, and Embase. The season in which RSV epidemics occur typically depends on geographical location and altitude. It is likely that several factors interact in complex ways in the development of epidemics under favorable climatic conditions. Keywords: Respiratory syncytial virus; RSV; Seasonality; Lower respiratory tract infection; Children; Developing countries