Assessment of the Public Health Impact of Zika Virus Disease on the Population of Brazil in 2015
The Zika Virus (ZIKV) is a re-emerging flavivirus that remains notable for its aetiological role in Zika
Virus Disease (ZVD) (Barzon et al., 2016). Species of Aedes mosquitoes act as the predominant mode
of transmission to a human host (Peterson et al., 2016). In addition, the ZIKV utilises non-vector
borne transmission in bodily fluids during sexual activity, blood transfusions, and occupational
exposure (Tesh and Weaver, 2012). In pregnancy, a ZIKV infection may also be transferred to the
foetus, via the transplacental route (Martinez, 2016).
Prior to 2015, African and Asian lineages of ZIKV strains were considered as insignificant human
pathogens, due to their association with benign infections (Simonin et al., 2017). However, in 2015,
an epidemic of severe ZVD emerged across the Americas. ZVD was subsequently declared an
emergency by the World Health Organisation (WHO) for nine months (WHO, 2016). It is
hypothesised that severe ZVD has arisen from new strains and is influenced by host immunity to
other flaviviruses (Schultz et al., 2017). Brazil is one such country at high-risk of severe ZVD that is
linked to sequalae such as microcephaly, and Guillain Barré Syndrome (GBS) (Gatherer and Kohl,
2016). Limited funding for disease control and medical supplies has allowed the ZIKV to persist
within Brazil (Gatherer and Kohl, 2016). This report aims to establish the health impact of ZVD on the
Health Impact on the Brazilian Population
The first case of ZVD in Brazil was confirmed in May 2015 by the Brazilian Ministry of Health (BNH),
and reported to the Center for Disease Control (CDC) (Heukelbach et al., 2016; Diniz et al., 2016;
Lammert et al., 2017). The outbreak began to disperse from northeastern regions towards the south,
which led to further reported cases across Brazilian states (Bogoch et al., 2016). Moreover, the
prevalence of microcephaly had also increased from 10 to 140 cases in 2015, correlating with a
history of post-ZIKV infection (Rasmussen et al., 2016). A causal link was later established between
pre-natal ZIKV exposure and the development of foetal microcephaly (Rasmussen et al., 2016).
The cases of ZVD in Brazil form a considerable proportion of the 217, 332 cases reported globally
between 2015 and mid-2017, prompting an international strategy for disease control (Table 1)
(WHO, 2016). Brazil was confirmed to have 135, 740 cases of ZVD between 2015 and 2017, which
was lower than the predicted cases by the Department of Defence (DD) (Table 1). This suggests that
control measures such as the use of mosquito nets and pesticides were effective in preventing some
ZIKV infections (Hayes, 2009). However, the confirmed number may not reflect the actual cases as
the symptoms of ZVD may have been mistaken for other arbovirus diseases (Saad-Roy et al., 2016).
The mortality of individuals with ZVD in Brazil exhibited an overall decline, with no deaths recorded
in 2017 (Table 1). This may due to the early detection of the disease, resulting in fewer
complications, including death. On the other hand, survivors of severe ZVD may not have access to
medical care, adversely impacting their health and quality of life (Freitas et al., 2016).
Table 1: Recorded Cases and Death Rates of ZVD in Brazil
Between 2015 and 2016, the suspected number of ZIKV infections and associated morbidities
(microcephaly and GBS) was recorded in north-eastern Brazil (Figure 1). During 2015 and 2016, the
number of GBS and suspected ZIKV increased and declined across similar ranges (Figure 1). However,
the number of ZIKV cases was lower than the number of GBS cases, which was suggestive of many
undiagnosed ZIKV infections (De Oliviero et al., 2017).
Consequently, a ZIKV infection may trigger GBS, whereby an autoimmune response leads to the
destruction of peripheral nerves, and ultimately paralysis (Estridge and Iskander, 2015; Verboon et
al., 2017). GBS may result in impaired mobility which increases the risk of cardiovascular disease
(Verboon et al., 2017). It may also become difficult to work, predisposing an affected individual to
poverty (Eisenstein, 2016). Furthermore, financial deprivation may limit access to medical care,
contributing to a premature death (Eisenstein, 2016). A peak in the incidence of microcephaly
occurred in 2015, approximately 23 weeks after a rise of GBS and ZIKV cases (Figure 1).
It was estimated that the number microcephaly cases would peak in 2016, following the resurgence
of GBS and ZIKV (Figure 1). Despite this, the number of microcephaly cases did not increase,
suggesting that the cases of GBS were linked to another arbovirus such as chikungunya (Cardosa et
al., 2017). Public awareness of ZVD may have also led to fewer conceptions, and hence reduced
cases of microcephaly (Hayes, 2009). Due to Brazil’s range of ethnic backgrounds, the individuals’
with ZVD may exhibit diversity in the gene pool, which may play a role in host susceptibility and the
severity of ZVD (Massad et al., 2017). Ethnicity remains a significant consideration as it may help
identify whose health will be impacted the most.
In summary, it was established that the re-emergence of the ZIKV has been associated with serious
complications including GBS and microcephaly. Furthermore, ZVD has the potential to exert
devastating health effects including a shortened life span and reduced quality of life. The extent of
illness is precipitated by socioeconomic factors, lifestyle choices, clinical interventions and
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Assessment of the Public Health Impact of Zika Virus Disease on the Population of Brazil in 2015