Essay: Controversies in Epidemiology of Nipah Virus Outbreaks

This essay critically examines the epidemiological aspects of Nipah virus (NiV) outbreaks, focusing on contemporary exposure-outcome associations. It explores the virus's zoonotic nature, transmission routes from animals (particularly bats and pigs) to humans, and associated risk factors. The e...Read More

Running head: ESSAY
Controversies in Epidemiology
Name of the Student
Name of the University
Author Note

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Introduction - Epidemiology refers to the study that encompasses the prevalence of a
particular disease in different population, and the underlying factors that governs its
distribution. Epidemiology is also associated with determinants of events for health-related
conditions, and their implementation for the effective prevention and management of diseases
(Fletcher, 2019). These studies are also conducted with the aim of determining risk factors,
which might provide the representation of crucial control point, in relation to food production
system. Nipah virus (NiV) has been identified to be a zoonotic virus that is typically transmitted
from animals to human beings (World Health Organization, 2018). However, it can also get
transmitted to humans directly, or through the consumption of contaminated food. This essay
will critically determine the contemporary exposure outcome association, in relation to outbreak
of Nipah virus from epidemiological literature.
Contemporary exposure-outcome association- Outcome of the NiV is typically defined
by the signs and symptoms that appear within 5-14 days of exposure of the affected individual.
The primary outcomes are headache, fever, drowsiness, concomitant with mental confusion and
disorientation (Rikhabchand, Kumbhare, Abhale, Bhoir & Agrawal, 2019). If left untreated, the
symptoms rapidly progress into coma within 24-48 hours. Some other outcomes that are
characteristic of the disease are inflammation of the brain, commonly known as encephalitis that
has been identified as a fatal complication of the infection. The condition is also characterized by
respiratory illness during the early stages. Secondary outcomes also include
seizures, neurological consequences like personality changes, and atypical pneumonia (World
Health Organization, 2018).
The first outbreak had been identified during 1999 in Kampung Sungai Nipah village at
Malaysia amongst pig farmers (Henry, 2019). However, no new outbreak reports had been

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reported in the nation since then. In the year 2001, an outbreak was also identified in
Bangladesh, and every year annual outbreaks are observed in recent times (Hegde et al., 2016).
Some other regions identified at the risk of this infection are namely Indonesia,
Ghana, Cambodia, the Philippines, Madagascar, and Thailand. In the year 2018, a major
outbreak was also reported from Kozhikode district in Kerala that resulted in as much as 21
deaths, which comprised of one healthcare worker as well (Chandni et al., 2019). Although the
outbreak was declared to be officially over by June 2018, on May the following year, a young
student was also diagnosed with the condition, and later on got released, after several months of
treatment. Despite lack of evidence regarding the association between prevalence and incidence
of the outcome with specific socio-demographic population, the disease is considered as threat to
different countries of South and Southeast Asia (Sachan, Verma, Jain, Kumar & Kharya, 2019).
Nature of the association- Reports from the Centres for Disease Control and Prevention
(2020) suggest that NiV infection is closely associated with contact of human beings with pigs
that are infected with the virus. In India and Bangladesh, the virus infection has been found to be
more frequent, and clear exposure has also been established to contact of humans with fruit bats,
or consumption of raw date palm sap. Cortes et al. (2018) analysed data that had been collected
from an approximate 57 bat-to-human spillovers that occurred during 2007-13. It was found that
difference in temperature provided an explanation for the 36% year-to-year inconsistency in the
total number of events that occurred during winter. In addition, distance to the hospitals where
surveillance was conducted also elucidated 45% of spatial heterogeneity. This was consistent
with Thanapongtharm et al. (2019) who conducted a multi-criteria decision analysis for mapping
contact zones located between epizootic risk factors that were local. Experts identified special
risk factors of the virus transmission amongst pigs of three different categories namely, (i)

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intermediate host factors like population density of pigs, (ii) natural host factors like distance to
bat colony or areas preferred by bats, and (iii) environmental factors like distance to orchard,
forest, water body or human population density.
Mourya et al. (2019) also determined the spatial association between outbreaks of NiV in
India with its infection amongst Pteropus bats. The findings suggested that outbreak of the
infection in Kerala was the direct consequence of wildlife human interaction in regions where
transmission occurred through contact with items that had been contaminated by bats, or direct
handling of bats. While consumption of palm sap was not considered the likely transmission
route in India, high NiV positivity in the study was identified in throat swab obtained from bats.
Additionally, persistence of NiV for few hours on fruits that have been contaminated was also
found to increase the probability of human infection.
Evidence associated- Nahar et al. (2017) evaluated the effects of behaviour modified
communication intervention on the consumption of raw sap that were potentially
NiV contaminated. On implementing interventions into different areas with “do not drink raw
sap” message and “only safe sap” message, it was found that 40% respondents were aware of
contracting the disease through consumption of raw sap, in comparison to control. The
participants directly exposed to the message “only safe sap” demonstrated the likelihood of
consuming raw sap from a source that was protected, in comparison to those without any
exposure (25 vs. 15%, OR 2.0, 95% CI 1.5–2.6, P < 0.001). Similar findings from Chakraborty
et al. (2016) affirmed that consumption of raw date palm sap acts as the primary route of
transmission of NiV from fruit bats to individuals. On analysing responses to in-depth
interviews, structured questionnaires and group discussions, it was found that direct contact with
an infected person and consumption of raw date palm sap were significant risk factors, in

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absence of which the operating transmission routes only comprised of consumption of fermented
date palm sap.
It has been established Pallivalappil et al. (2020) that out of the 23 patients who had been
infected in Kerala in 2018, the index case was the only one that had been infected from fruit
bats. The remaining patients had acquired the infection due to virus transmission from three
healthcare organisations that resulted in signs and symptoms of fever, tachycardia, altered
sensorium, segmental myoclonus, and hypertension.
This was in accordance to Thomas et al. (2019) who identified the fact that the natural
reservoir of NiV was fruit bats that belong to the Pteropus genus, and also elaborated on
isolation of the virus from bat urine and fruits that had been partially consumed in Malaysia. The
researchers initiated contact surveillance in addition to verbal autopsy of death reports and field
visits, for eliciting details of the exposure. It was found that of the 18 cases that had been
confirmed, there was a fatality rate of 88.8%, with the mean incubation period of approximately
nine days. The human to human transmission was identified as the major exposure with the index
case serving as a source of infection for 15 additional cases that also included healthcare
workers. As claimed by Arunkumar et al. (2019) of all the 23 cases that had been identified in
India in the year 2018, the lineage of the virus that was found associated to the outbreak
demonstrated significant similarity to the Bangladesh lineage. With an incubation period of 9.5
days, the major risk factors for exposure included close proximity with an infected person, such
as, feeding, nursing, or touching, thereby enabling droplet infection exposure.
Methodological limitations- The major methodological limitation during interpretation of
association between exposure and outcome was insecurity, which might have prevented the

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researchers and survey workers from adequately carrying out the process of data
collection. Absence of appropriate resources and methods also prevented the healthcare workers
from appropriately submitting data related to surveillance of the affected patients. Lack of proper
access facilities gave rise to problems encountered in transport and communication to remote
areas where the people had been affected with the infection, and might have resulted in bias.
Epidemiological results are also constrained by the quick alterations that occur in the nutritional
status and health of populations which are emergency-affected (Fletcher, 2019). By the time the
researchers collected data and analysed them, the characteristics of the population might have
been changed, thus preventing generalisability of the findings.
Another significant limitation of epidemiological literature was program evaluation. It is
typically impossible to determine the impact on health, without conducting randomised
controlled trials, since a range of factors might simultaneously create an influence on a particular
health outcome, which in turn would lead to failure in establishing causal association between an
exposure and an outcome (Giesecke, 2017). Additionally, one significant limitation of this
literature can be accredited to the fact that majority of the decisions that are taken at the time of
medical emergencies are dependent on resource limitations, public relations, personal priorities,
or political concern, which often lead to irrational programmed decisions, thereby affecting
epidemiological evidences. Additionally, failure to adjust the confounding factors might have
also created an impact on the findings. However, the evidences presented in the aforementioned
sections, in relation to contact with affected pigs and bats, consumption of contaminated fruits,
and direct contact with affected individuals are coherent and consistent.
Conclusion- Thus, it can be concluded that, epidemiological methods are particularly
utilised for disease surveillance, which helps in identification of risk factors that influence health

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and wellbeing of individuals. While the first recognised outbreak of NiV was associated with
direct contact of individuals with infected pigs or their contaminated tissues, subsequent
outbreaks that occurred in India and Bangladesh established the cause and effect association with
consumption of fruit products that had been contaminated with saliva or urine from the infected
bats. Infection in one patient eventually resulted in transmission of the infection in the
community through close contact with excretion and secretion of the affected individual.
Therefore, it can be suggested that this association is one of cause and effect.

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References
Arunkumar, G., Chandni, R., Mourya, D. T., Singh, S. K., Sadanandan, R., Sudan, P., &
Bhargava, B. (2019). Outbreak investigation of Nipah virus disease in Kerala, India,
2018. The Journal of infectious diseases, 219(12), 1867-1878.
Centers for Disease Control and Prevention. (2020). Nipah Virus- Risk of Exposure. Retrieved
from https://www.cdc.gov/vhf/nipah/exposure/index.html
Chakraborty, A., Sazzad, H. M. S., Hossain, M. J., Islam, M. S., Parveen, S., Husain, M., ... &
Daszak, P. (2016). Evolving epidemiology of Nipah virus infection in Bangladesh:
evidence from outbreaks during 2010–2011. Epidemiology & Infection, 144(2), 371-380.
Chandni, R., Renjith, T. P., Fazal, A., Yoosef, N., Ashhar, C., Thulaseedharan, N. K., ... &
Remla Beevi, A. (2019). Clinical Manifestations of Nipah Virus–Infected Patients Who
Presented to the Emergency Department During an Outbreak in Kerala State in India,
May 2018. Clinical Infectious Diseases.
Cortes, M. C., Cauchemez, S., Lefrancq, N., Luby, S. P., Jahangir Hossain, M., Sazzad, H. M., ...
& Gurley, E. S. (2018). Characterization of the spatial and temporal distribution of Nipah
virus spillover events in Bangladesh, 2007–2013. The Journal of infectious
diseases, 217(9), 1390-1394.
Fletcher, G. S. (2019). Clinical epidemiology: the essentials. Lippincott Williams & Wilkins.
Giesecke, J. (2017). Modern infectious disease epidemiology. CRC Press.

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Hegde, S. T., Sazzad, H. M., Hossain, M. J., Alam, M. U., Kenah, E., Daszak, P., ... & Gurley, E.
S. (2016). Investigating rare risk factors for Nipah virus in Bangladesh: 2001–
2012. Ecohealth, 13(4), 720-728.
Henry, R. (2019). Etymologia: Nipah Virus. Emerging Infectious Diseases, 25(5), 1010.
Mourya, D. T., Yadav, P., Sudeep, A. B., Gokhale, M. D., Gupta, N., Gangakhedkar, R. R., &
Bhargava, B. (2019). Spatial Association Between a Nipah Virus Outbreak in India and
Nipah Virus Infection in Pteropus Bats. Clinical Infectious Diseases.
Nahar, N., Paul, R. C., Sultana, R., Sumon, S. A., Banik, K. C., Abedin, J., ... & Gurley, E. S.
(2017). A controlled trial to reduce the risk of human Nipah virus exposure in
Bangladesh. EcoHealth, 14(3), 501-517.
Pallivalappil, B., Ali, A., Thulaseedharan, N. K., Karadan, U., Chellenton, J., Dipu, K. P., ... &
Kumar, G. S. (2020). Dissecting an outbreak: A clinico-epidemiological study of Nipah
virus infection in Kerala, India, 2018. Journal of Global Infectious Diseases, 12(1), 21.
Rikhabchand, S. A., Kumbhare, M. R., Abhale, A. U., Bhoir, A. A., & Agrawal, S. P. (2019).
Public Health concern for a Nipah Virus disease.
Sachan, D., Verma, M. K., Jain, P. K., Kumar, S., & Kharya, P. (2019). Nipah virus outbreak: A
comparative study from Southeast Asia. Indian Journal of Community Health, 31(2).
Thanapongtharm, W., Paul, M. C., Wiratsudakul, A., Wongphruksasoong, V., Kalpravidh, W.,
Wongsathapornchai, K., ... & Gilbert, M. (2019). A spatial assessment of Nipah virus
transmission in Thailand pig farms using multi-criteria decision analysis. BMC veterinary
research, 15(1), 73.

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Thomas, B., Chandran, P., Lilabi, M. P., George, B., Sivakumar, C. P., Jayadev, V. K., ... &
Hafeez, N. (2019). Nipah virus infection in Kozhikode, Kerala, South India, in 2018:
Epidemiology of an outbreak of an emerging disease. Indian Journal of Community
Medicine: Official Publication of Indian Association of Preventive & Social
Medicine, 44(4), 383.
World Health Organization. (2018). Nipah virus. Retrieved from https://www.who.int/news-
room/fact-sheets/detail/nipah-virus