International Journal of Basic & Clinical Pharmacology | September 2020 | Vol 9 | Issue 9 Page 1444 International Journal of Basic & Clinical Pharmacology Iribhogbe OI et al. Int J Basic Clin Pharmacol. 2020 Sep;9(9):1444-1453 http://www.ijbcp.com pISSN 2319-2003 | eISSN 2279-0780 Systematic Review Human influenza viruses in South-East and East Asia: a systematic review of seasonal patterns, viral types/subtypes, and antiviral susceptibility pattern in the past two decades Osede Ignis Iribhogbe 1 *, Sunday Olowo Samuel 2 , John O. Ohaju-Obodo 3 INTRODUCTION Influenza viruses are respiratory viruses that belong to a family of viruses known as orthomyxoviridae. 1,2 They have been implicated in seasonal outbreaks, epidemics, and pandemics in the past two decades. 1,3 Research has shown that nineteen of the genetically distinct types have shown reassortment since the 1918 Spanish flu which ravaged the world and claimed over 20-50 million lives globally. 1,4 Additionally, six strains of the genetically distinct subtypes are known to have human-to-human transmission, ten are zoonotic avian influenza viruses 1 Department of Pharmacology and Therapeutics, 2 Department of Medical Microbiology, College of Medicine, Ambrose Alli University, Ekpoma Edo State, Nigeria 3 Department of Pharmacology and Therapeutics, College of Health Sciences, Delta State University, Abraka Delta State, Nigeria Received: 07 July 2020 Revised: 09 August 2020 Accepted: 10 August 2020 *Correspondence: Dr. Iribhogbe Osede Ignis, Email: osedeignis@gmail.com Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. DOI: http://dx.doi.org/10.18203/2319-2003.ijbcp20203634 ABSTRACT The study aims to evaluate influenza seasonality pattern and identify influenza viral types/subtype as well as their antiviral susceptibility pattern in South-East (SE) and East Asia (E-Asia) with the view of providing useful information for public health action. The study is a systematic review of existing literature involving the use of search engines such as Google Scholar, PubMed and EBSCOHOST. The search was conducted using a multi-stage approach which yielded 66 articles after screening for relevance to the subject using specific inclusion and exclusion criteria. A total of 60 articles were eventually analyzed and the findings were presented in tables and bar charts. The study showed that the influenza virus was more prevalent in the 6-20 years age group (SE: 53.3% and E-Asia: 44.8%) and also occurred commonly in the age of 61-90 years age group (SE: 15.6% and E-Asia: 24.1%). Seasonal peaks were reported more in the winter period with influenza A (H1N1) pdm09 (22.37%; 24.14%), seasonal influenza A (H1N1) (6.58%; 17.24%), A (H3N2) (11.84%; 17.24%), and influenza B Victoria/Yamagata (5.26%; 20.69%) being the predominant viral type/subtypes. The pathogenic avian influenza strains; AH5N1 (7.89%) and A (H7N9) (6.90%) was also reported in SE and E-Asia respectively. Oseltamivir (37.5%) and peramivir (37.04%) were the most frequently used anti-influenza agents in SE and E-Asia respectively. However, an H55Y+I436N combined mutation 4 (12.5%) and an H274Y amino acid substitution 5 (18.5%) in the neuraminidase gene of influenza A (H1N1) pdm09 was associated with decreased sensitivity to neuraminidase inhibitors. The study has shown that influenza A (H1N1) pandemic and seasonal strain, A (H3N2), and B Victoria/Yamagata remains the predominant circulating virus in SE and E-Asia. However, the dynamic antigenic and genetic evolution of the virus calls for more frequent surveillance in the region. Keywords: Viral types/subtypes, Seasonality, Antiviral agents, Antiviral susceptibility