Phylogeographic analysis of human influenza A and B viruses in Myanmar, 2010–2015

Abstract

We investigated the circulation patterns of human influenza A and B viruses in Myanmar between 2010 and 2015 by analyzing full HA genes. Upper respiratory tract specimens were collected from patients with symptoms of influenza-like illness. A total of 2,860 respiratory samples were screened by influenza rapid diagnostic test, of which 1,577 (55.1%) and 810 (28.3%) were positive for influenza A and B, respectively. Of the 1,010 specimens that were positive for virus isolation, 370 (36.6%) were A(H1N1)pdm09, 327 (32.4%) were A(H3N2), 130 (12.9%) B(Victoria), and 183 (18.1%) were B(Yamagata) viruses. Our data showed that influenza epidemics mainly occurred during the rainy season in Myanmar. Our three study sites, Yangon, Pyinmana, and Pyin Oo Lwin had similar seasonality and circulating type and subtype of influenza in a given year. Moreover, viruses circulating in Myanmar during the study period were closely related genetically to those detected in Thailand, India, and China. Phylogeographic analysis showed that A(H1N1)pdm09 viruses in Myanmar originated from Europe and migrated to other countries via Japan. Similarly, A(H3N2) viruses in Myanmar originated from Europe, and disseminated to the various countries via Australia. In addition, Myanmar plays a key role in reseeding of influenza B viruses to Southeast Asia and East Asia as well as Europe and Africa. Thus, we concluded that influenza virus in Myanmar has a strong link to neighboring Asian countries, Europe and Oceania.

Epidemic of influenza A(H1N1)pdm09 analyzed by full genome sequences and the first case of oseltamivir-resistant strain in Myanmar 2017

“…Myanmar has a tropical monsoon climate with three seasons: winter (November-February), summer (March-Mid May), and rainy (Mid May-October) seasons, based on the analysis of pressure, rainfall, and temperature [26]. The study showed that the circulation of influenza viruses peaked in July, which is consistent with previous studies showing that the influenza season in Myanmar peaked in July or August, during the rainy season [6][7][8]. This observation is also similar to the national surveillance data reported to the regional and global influenza surveillance platform (FluNET), which showed that the regional influenza outbreak started during the rainy season from July (week 29) to September (week 36), and influenza virus activity peaked in August with 369 flu-positive cases during the reported weeks 31-35 in 2017 [27].…”

“…Since then, it has been co-circulating with other seasonal influenza viruses in the country. Previously, we reported the epidemiology and genetic characterization of influenza virus A and B circulating in Myanmar [6,7] and characterized the drug-susceptibility of seasonal and pandemic influenza A(H1N1) viruses in Myanmar in 2008 and 2009 [8]. Only 16 sporadic cases of A(H1N1)pdm09 were detected in 2009, and genotyping of these viruses showed no mutations in neuraminidase (NA), which indicated susceptibility to oseltamivir [8].…”

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

“…However, the antigenic and genetic evolutionary dynamics of the virus have resulted in the emergence of several subtypes and clades which have been quit diverse across the region. 35 For instance, there are reports of the emergence of the new clade 1.1.2 and 2.3.2.1 reassortant A(H5N1) virus and clade 3c.2a and 3c.3a A(H3N2) virus between 2012-2015. 15,17 Within this same period, other new reassortant clades were detected for influenza A (H3N2) and B viruses in Laos PDR, Taiwan, Malaysia, Myanmar, Thailand, Japan, China and Vietnam.…”

“…15,17 Within this same period, other new reassortant clades were detected for influenza A (H3N2) and B viruses in Laos PDR, Taiwan, Malaysia, Myanmar, Thailand, Japan, China and Vietnam. 35,36 The finding implies that there is the need for a sustained approach in the regions periodic update of information provided to the WHO global influenza surveillance response (GISRS) system which is a mechanism designed by the WHO for deciding the antigenic and genetic composition of influenza vaccines used in the different hemispheric zones. 5,21,27 Currently, WHO has approved the use of trivalent or quadrivalent vaccines that protect against the three predominant strains which are; influenza A (H1N1), A (H3N2), and B viruses in most countries.…”

Increasing Hemagglutination Inhibition Antibodies against Two Lineages of Type B Influenza Virus in 2017-2018 Winter Season in Beijing, China

“…For a long time, much effort has been done on Flu A virus, whereas Flu B virus was relatively less investigated, resulting in poor lineage matches with recommended in uenza vaccine strains and the control options require further improvement (Htwe et al 2019;Noh et al 2018). HI tests measure the presence of speci c antibodies of IgG in sera that inhibit virus-mediated agglutination of erythrocytes (Rowe et al 1999).…”