Dynamics of Influenza Seasonality at Sub-Regional Levels in India and Implications for Vaccination Timing

Abstract

BackgroundInfluenza surveillance is an important tool to identify emerging/reemerging strains, and defining seasonality. We describe the distinct patterns of circulating strains of the virus in different areas in India from 2009 to 2013.MethodsPatients in ten cities presenting with influenza like illness in out-patient departments of dispensaries/hospitals and hospitalized patients with severe acute respiratory infections were enrolled. Nasopharangeal swabs were tested for influenza viruses by real-time RT-PCR, and subtyping; antigenic and genetic analysis were carried out using standard assays.ResultsOf the 44,127 ILI/SARI cases, 6,193 (14.0%) were positive for influenza virus. Peaks of influenza were observed during July-September coinciding with monsoon in cities Delhi and Lucknow (north), Pune (west), Allaphuza (southwest), Nagpur (central), Kolkata (east) and Dibrugarh (northeast), whereas Chennai and Vellore (southeast) revealed peaks in October-November, coinciding with the monsoon months in these cities. In Srinagar (Northern most city at 34°N latitude) influenza circulation peaked in January-March in winter months. The patterns of circulating strains varied over the years: whereas A/H1N1pdm09 and type B co-circulated in 2009 and 2010, H3N2 was the predominant circulating strain in 2011, followed by circulation of A/H1N1pdm09 and influenza B in 2012 and return of A/H3N2 in 2013. Antigenic analysis revealed that most circulating viruses were close to vaccine selected viral strains.ConclusionsOur data shows that India, though physically located in northern hemisphere, has distinct seasonality that might be related to latitude and environmental factors. While cities with temperate seasonality will benefit from vaccination in September-October, cities with peaks in the monsoon season in July-September will benefit from vaccination in April-May. Continued surveillance is critical to understand regional differences in influenza seasonality at regional and sub-regional level, especially in countries with large latitude span.

National Influenza Surveillance in the Philippines from 2006 to 2012: seasonality and circulating strains

“…Thus, April to May is the most appropriate month for influenza vaccination for the Philippines and countries with similar seasonality [5]. In areas in India north of 30° N however, there was also increased influenza activity during winter, so that a separate vaccination timing has been recommended [5, 24, 25] for this country. In contrast, tropical countries in Asia below 11° N like Indonesia (Jakarta, 6.2° N), Malaysia (Kuala Lumpur, 3.2° N), and Singapore (1.3° N), influenza was found all throughout the year with no distinct influenza season [5].…”

“…In contrast, tropical countries in Asia below 11° N like Indonesia (Jakarta, 6.2° N), Malaysia (Kuala Lumpur, 3.2° N), and Singapore (1.3° N), influenza was found all throughout the year with no distinct influenza season [5]. Specific analysis on the association between influenza activity and climate variables has not been done in this study but June to November coincides with the rainy season in the Philippines similar to that of Cambodia [27], Myanmar [28], North Thailand [29], Bangladesh [5, 30], Lao [31], and some parts of India South of Srinagar [24, 25]. Factors other than the rainy season might also play a role for the increased influenza virus activity starting the month of June in the Philippines.…”

Respiratory viruses in acute exacerbations of chronic obstructive pulmonary disease

“…Kashmir has a temperate geography in contrast with the generally more tropical climate in the rest of the country, and we have earlier reported a temperate seasonality of influenza virus circulation[56] which contributes to the exacerbations of COPD in 8% cases. [4] Demographic and clinical parameters were recorded in each case.…”

An Experience of Pandemic Influenza A (H1N1) 2009 Virus Outbreak in 2017 at Tertiary Care Hospital, Chennai, Tamilnadu, India

“…The relationship to the influenza virus with low temperature reported from the states of India Jain et al, 2009;Koul et al, 2014;Chadha et al, 2015) The case fatality rate (CFR) was less than 1.9% compared to other states of India and equal to previous studies from Tamilnadu (Puvanalingam et al, 2011). The CFR was found to be 12.…”