Epidemiological and evolutionary dynamics on influenza B viruses in Kuala Lumpur, Malaysia between 2012 to 2014 / Oong Xiang Yong
Epidemiological and evolutionary dynamics of influenza B Victoria and Yamagata lineages remain poorly understood in the tropical Southeast Asia region, despite causing seasonal outbreaks worldwide. The aim of this study was to understand the epidemiological, evolutionary and transmission dynam...
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| Format: | Thesis |
| Published: |
2016
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| Online Access: | http://studentsrepo.um.edu.my/7093/4/xiang_yong.pdf http://studentsrepo.um.edu.my/7093/ |
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| Summary: | Epidemiological and evolutionary dynamics of influenza B Victoria and Yamagata
lineages remain poorly understood in the tropical Southeast Asia region, despite causing
seasonal outbreaks worldwide. The aim of this study was to understand the
epidemiological, evolutionary and transmission dynamics, as well as the clinical
profiles of influenza B lineages circulating in Kuala Lumpur, Malaysia from 2012 to
2014 in a predominantly adult population. Furthermore, meteorological factors that may
play a role in influenza seasonality in this country were also investigated. During the
study period, nasopharyngeal swab samples collected from adult outpatients
experiencing acute upper respiratory tract infection symptoms were screened for
influenza viruses using a multiplex RT-PCR assay. Among 2,010/3,935 (51.1%)
patients infected with at least one respiratory virus, 287 (14.3%) and 183 (9.1%)
samples tested positive for influenza A and B viruses, respectively. Influenza-positive
cases correlated significantly with meteorological factors - total amount of rainfall,
relative humidity, number of rain days, ground temperature and particulate matter
(PM10). Phylogenetic reconstruction of haemagglutinin (HA) gene from 168 influenza
B viruses grouped them into Yamagata Clade 3 (65, 38.7%), Yamagata Clade 2 (48,
28.6%) and Victoria Clade 1 (55, 32.7%). With the phylogeny based on neuraminidase
(NA) gene, 30 intra-clade (29 within Yamagata Clade 3, 1 within Victoria Clade 1) and
1 inter-clade (Yamagata Clade 2-HA/Yamagata Clade 3-NA) reassortants were
identified. Study of virus temporal dynamics revealed a lineage shift from Victoria to
Yamagata (2012-2013), and a clade shift from Yamagata Clade 2 to Clade 3 (2013
2014). Yamagata Clade 3 predominating in 2014 consisted of intra-clade reassortants
that were closely related to a recent WHO vaccine candidate strain
(B/Phuket/3073/2013), with the reassortment event occurred approximately 2 years ago
based on Bayesian molecular clock estimation. Malaysian Victoria Clade 1 viruses
v
carried H274Y substitution in the active site of neuraminidase, which confers resistance
to oseltamivir. Clinical and demographic data showed that Yamagata-infected patients
were older and more likely to experience headache while Victoria-infected patients
were more likely to experience nasal congestion and sore throat. This study describes
the evolution of influenza B viruses in Kuala Lumpur, Malaysia and highlights the
importance of continuous surveillance to inform influenza vaccination policies in this
region. |
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