The Zika Epidemic in Latin America

The Zika virus is one of a handful of viruses that has only recently made the jump from animals to humans (Faria et al, 2016). It was first recorded infecting humans in Uganda in 1952, and since then, it has spread through areas of Africa and French Polynesia, maintaining a relatively low profile until the first significant outbreaks were recorded in 2013 in these areas (Lesser & Kitron, 2016). In Latin America, this was not a disease that doctors had heard of, let alone were on the lookout for, when the first cases appeared in the Brazilian city of Salvador in 2014 (Lowe et al, 2018). In May of 2015, the presence of the disease was confirmed by the Brazilian Ministry of Health, identified in a total of 16 individuals (Diniz et al, 2016). In November of 2015, Brazil declared the presence of Zika in the country a national public health emergency, and it was not until April of 2016 -- a full year after the virus had been officially detected in Brazil -- that the WHO classified Zika and its newly discovered link to microcephaly in babies as an international emergency situation (Ministerio da Saude Brasil, 2015; WHO, 2016).

Part of the reason why it took time for the world to realize the threat that Zika presented was that its symptoms strongly resemble the symptoms of well-known endemic diseases in Latin America, such as dengue or chikungunya (Diniz, 2016). Zika presents with a rash, fever, and headache, which generally do not escalate enough to merit a trip to a hospital or even a doctor (Paixão et al, 2016). In the early days of the Zika epidemic in Brazil, many people who later found that they had contracted Zika reported to their doctors that they had originally dismissed the infection as a mild case of dengue (Diniz, 2016). These fairly generalizable symptoms associated with Zika and their overlap with many more recognizable and often more immediately serious diseases has had several effects on the spread of the disease in Latin America. It has made the virus much more difficult to track and quantify, meaning that the health statistics that public health experts rely on in their decision-making processes often have large margins of error related to underreporting or misdiagnosis, especially when considering the early days of the epidemic. It also meant that when the virus first came to Latin America, it took many months for officials to even realize that there was a new disease spreading in South America, let alone mount a targeted and effective response to the disease (Diniz, 2016).

The first cases in Latin America were reported in northeastern Brazil, a historically remote and impoverished region that is far away from the scientific and medical centers in Rio de Janeiro (Lowe et al, 2018; Diniz, 2106). It was at first largely considered a benign disease -- uncomfortable, but far from deadly -- until childbirth and maternity specialists in Recife began to report strange increases in the proportion of babies born with microcephaly (Diniz, 2016). Microcephaly is usually extremely rare: characterized by smaller-than average head size and brain mass at birth, only about 2 in 10,000 babies in the U.S. (a country not strongly affected by Zika) are born with the condition (CDC, 2017). Dr. Adriana de Oliveira Melo, a neurological obstetrician in Northeastern Brazil, reported seeing 3 or 4 cases of this rare condition within a single month -- a sign that something new was driving an increases in fetal brain damage (Diniz, 2016). The idea that the Zika virus could be linked to microcephaly was pushed by doctors observing these changes early on, but a delayed government response, driven both by controversy surrounding the hypothesis and by a lack of adequate RT-PCR testing equipment in most Brazilian states, meant that this link between the virus and a devastating fetal development problem was not officially reported until 2016, leaving many women and their children to suffer from the worst impacts of the virus without knowing what caused it (Diniz, 2016; Lowe et al, 2018). During this time, the incidence of microcephaly in newborn babies increased from about 2-5 per 10,000 births, to 50 cases per 10,000 births in Northeastern Brazil (Oliveira et al, 2017).

The biggest threat from this disease, then, is not actually the disease itself -- but rather the devastating effects that it can have on a developing fetus. This presents a complicated public health problem: the most pressing concern around Zika is not transmission or infection in the normal way -- by mosquito -- but rather the vertical transmission of the disease from mother to fetus (Lowe et al, 2018). A developmental, rather than infectious, issue is the most concerning symptom of the disease. Developmental diseases are difficult, if not impossible, to treat effectively, and persist for the duration of that individual’s lifespan. Public health officials in Latin America are faced with the daunting task of addressing something that acts like a hereditary or genetic disease, but spreads like an infectious disease (Teixeira et al, 2016).

The severity of the effects of microcephaly are wide ranging -- with some babies being unable to swallow food, see, hear, or move on their own; and other babies being able to roll over, make noise, and eat without additional assistance (Ferreira et al, 2018). The characteristic effect of microcephaly is a general lack of responsiveness: babies with the condition don’t respond to auditory or visual stimulation, which suggests serious and compounding issues with brain development. The rarity of this condition prior to the spread of Zika has meant that health officials do not as yet know what the effects of this condition will be on babies in the long term (Satterfield-Nash, 2017). Many mothers who contracted Zika during pregnancy, but did not have a baby with noticeable microcephaly have expressed fear that the potential vertical transmission of the virus may have affected their child’s brain in an as-yet undetected way (Diniz, 2016). It is possible that less-severe effects of Zika exposure during gestation will present themselves during many children’s lifetimes in the guise of difficulty learning in school, worsening vision and hearing problems, and other neurological impairments that can only be diagnosed later in life (Diniz, 2016; Ventura et al 2016).

Clearly the effects of microcephaly are devastating to the child and its family -- but the impacts of these affected children will likely have a significant effect on often already overburdened economies in Latin America. These children and their families rely on expensive treatments and therapies provided by or subsidized by public health care, and many more pay out-of-pocket for treatments that the government does not pay for (Diniz, 2016). Mothers often have to quit their jobs in order to care full-time for their babies’ needs, which puts a further strain both on family budgets and overall economic production of the region (Harris et al, 2016).

In October of 2015, neighboring countries to Brazil began to report PCR-confirmed cases of the Zika virus, followed some months later by an uptick in microcephaly rates. Colombia, Suriname, and Panama were the first countries outside of Brazil to report detection of the virus, followed in December of 2015 by Paraguay, Guatemala, El Salvador, and Mexico (Kindhauser et al, 2016). By February of 2016, the Zika virus had spread to fill the range of it’s vector, the Aedes aegypti mosquito, infecting the majority of Latin America and the Caribbean (Zhang et al, 2017). Evidence began to emerge of non-vector based transmission; in Texas and Hawaii, doctors reported cases of Zika that appeared to have been spread via sexual contact (ECDC, 2019). The appearance of the virus in the U.S, as well as the increased uncertainty about the method of transmission and therefore the boundaries of the disease, caused a well-televised panic in the United States. However, despite the disproportionate amount of anxiety and new coverage, the virus barely appeared and rapidly fizzled out in North America. Even the other countries in Latin America that reported the presence of Zika saw just a fraction of the cases that occured in Brazil, and since 2016 those cases have largely disappeared. Zika was -- and is -- a disease that is heavily concentrated in Brazil, and is predicted to become seasonally endemic to this region (Colón-González, 2017; ECDC, 2019).

Northeastern Brazil has so far shouldered the greatest proportion of the burden. This is due in part to the natural range of the Aedes aegypti mosquito, but it is also heavily correlated with pre-existing poverty; poorer neighborhoods do not always have direct access to water, so families usually store it in large barrels that are the preferred breeding habitat of the mosquito (Carvalho et al, 2017; Carter, 2016). This, as well as fewer sanitation services and governmental resources overall, has resulted in a disproportionate distribution of the disease in the poorest areas that are often prohibitively far away from hospitals or clinics that can offer the necessary care to babies born with microcephaly (Lowe et al, 2016; Harris et al, 2016). Women, already occupying a traditionally disadvantaged socioeconomic position, are the ones who are shouldering most of the burden of the disease in terms of both responsibility and impact (Harris et al, 2016).

Those most affected by the disease are those with the fewest resources available to combat it, and this is an issue that will only grow as the children born with microcephaly -- still only babies -- continue to grow. Zika has faded from the global public consciousness and most of us in the United States or Europe have a sense of the crisis being averted -- but, as Zika settles into an endemic position alongside other mosquito-borne diseases like dengue, chikungunya, and yellow fever, the number of babies born with microcephaly is expected to steadily increase (Lowe et al, 2018; Diniz, 2016). The public health problem that this presents is looming -- and unresolved. However, if this long-term problem can be treated with long-term solutions in place of reactionary or stop-gap programs, the outward spread of this virus may yet be controlled.

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