The truth about Brazilian epidemics
The next Olympics and Paralympics games will be held in Rio de Janeiro, Brazil in August and September 2016. Together with athletes and guests from all over the world, uninvited visitors are also taking part in the event: three different viruses transmitted by mosquito bites. In this article, I give you information about the diseases and how you can protect yourself while attending the games.
The experienced competitor: Dengue virus
The Dengue virus, genus Flavivirus (Flaviviridae), is an old acquaintance to Brazilians. The first outbreak occurred in Roraima, northern Brazil, in 1980. Six years later, authorities reported the first cases in Rio de Janeiro and, after that, outbreaks sadly became the norm. Currently, the danger increased as the number of cases increased 30-fold and the Dengue fever became more severe than in the past. In October 2015, 693 people died from this disease in Brazil. There are no vaccines or anti-viral strategies available.
The basic symptoms include headaches, fatigue, muscle and joint pain, high fever (above 39°C), nausea, and rash. Affected individuals also reported pain in the back of the eyes.
The disease can evolve to a hemorrhagic form, which symptoms include bleeding, blood plasma leakage, and low level of blood platelets. It can also lead to a secondary infection, the dengue shock syndrome, which causes a severe low in blood pressure and can develop into death.
The copycat competitor: Chikungunya virus
The Chikungunya virus, genus Alphavirus (Togaviridae), arrived in Brazil quite recently. The first confirmed case occurred in 2010. Five years later, there was an outbreak in South America, with many cases reported in Brazil. The symptoms of Chikungunya fever resemble those of Dengue fever, but the joint pain is more severe in the former. The pain can persist for months after the acute phase of the disease. Although all joints are affected, the pain concentrates mostly in feet, hands, ankles, and wrists. The inflammatory process can cause edema. In some cases, an associated conjunctivitis (red eye) can also appear. No vaccines or anti-viral strategies are available. Fortunately, Chikungunya fever is rarely lethal. The deaths reported so far are related to complications in patients stricken by pre-existing diseases.
The rising star: Zika virus
The first contact scientists had with Zika virus was through a sentinel monkey in 1947, in the Zika Forest of Uganda, Africa, while they were inspecting the area for the presence of diseases. The virus belongs to the genus Flavivirus, which also includes dengue and yellow fever viruses.
In the beginning, the disease affected only apes bitten by infected mosquitoes. Later, the Zika fever began to affect humans. The first infected humans could not re-transmit the disease, as it happens now. Before the first outbreak in Yap, Federated States of Micronesia in 2007, authorities had reported only 14 cases in Africa and Asia. Approximately seven years later (2013-2014), a second outbreak occurred in the French Polynesia. That outbreak spread across the Pacific Islands, reaching South and Central Americas in 2015. The first case reported in Brazil occurred in April 2005.
The Zika fever is a mild disease, asymptomatic in 80% of the cases, popularly known as “mild Dengue”. In the other 20% of the cases, the symptoms include itchy rash, low or no fever, muscle or joint pain, and conjunctivitis (red eye). So what is the fuss about it? The problem arose when scientists discovered that Zika virus could be related to reported cases of baby malformation (microcephaly) and Guillain-barré syndrome.
The Zika Team: secondary diseases associated with the virus
The Guillain-barré syndrome
The Guillain-barré syndrome is a rare autoimmune disease triggered by multiple causes, including bacterial or viral infection, which appears two or three weeks after the infection. It usually affects two per 100,000 people every year. However, after the arrival of the Zika virus, Brazilian authorities reported 16 cases of the syndrome in Niterói, Rio de Janeiro, in a single month. Eight countries already reported an association between the Guillain-barré syndrome and the Zika virus. In the French Polynesia, for instance, the number of reported cases increased 20-fold since the outbreak of the virus.
In affected individuals, antibodies mistakenly attack the peripheral nervous system, damaging the myelin insulation and exposing peripheral nerves. Its symptoms include muscle weakness and movement and reflex loss on arms and legs. The paralysis can progress to face nerves, affect swallowing and even breathing capacity in more severe cases. Although the effects are reversible, the risk of a respiratory arrest during the acute phase cannot be ignored. Symptoms can persist for weeks. The treatment is expensive, as it can involve ventilator support and monitoring in intensive care units.
Individuals affected by microcephaly have an abnormally small cephalic perimeter. This feature appears naturally in 3% of the population with no other alteration. However, in addition to a smaller skull, this malformation can include closed fontanel, which restricts brain growth and compromises its development. Scientists also reported internal macrocalcifications, malformation of the central nervous system, and ocular alterations. There is no cure, and, in acute cases, the anomaly can lead to death. After scientists had confirmed the first case in Pernambuco, Brazil, in November 2015, the Ministry of Health reported 583 confirmed cases and 30 deaths.
Likewise the Guillain-barré syndrome, microcephaly can be associated with several causes. However, scientists found a strong correlation between the Zika virus in French Polynesia. In Brazil, scientists identified the virus in the amniotic fluid of pregnant women carrying embryos with microcephaly. The genome sequencing of that virus showed 97-100% homology with the Zika virus that caused the outbreak in French Polynesia.
Scientists also reported the presence of virus in saliva, urine, and blood, and secretions. As sexual transmission is a possibility, authorities recommend the same precautions used to avoid STDs.
The tour promoter: the mosquito
The three viruses are carried and transmitted by the mosquito Aedes aegypti. In the 1940s, large-scale mosquito control started. In the 1960s, A. eagypti was almost eradicated from the Americas and mosquito-borne diseases were no longer considered a threat.
However, when the mosquito population grew again 20 years later, the human population was not prepared to fight back. Scientists were no longer concerned about those diseases and had no short-term plan in hand. Unplanned urban grow, with plenty of sites for mosquito reproduction and resistance to insecticides made the process even more difficult. As a result, the situation got out of control.
Knowing the opponent
Adult mosquitoes feed on sweet substances, such as nectar, and fruits. Only the female bites, as it needs the protein present in blood to produce eggs. Biting is more intense at dusk and dawn and humans are preferred over other animals.
After a blood meal, a female produces a batch composed of 100-200 eggs. It needs to bite several times to complete meal, which increases the transmission risk. A female usually produces five batches during its life, strategically distributed in different sites.
The female lays eggs on clean or dirty stagnant water. It uses any water-filled container it finds, from plant saucers to abandoned tires. It can also use unusual places, such as the water compartment of frost-free fridges, toilet water tanks, and even shower stalls.
The eggs are sticky and can be attached to the walls of containers and survive drought for more than a year in a dormant state. Three months after rehydration, the eggs are ready to hatch. In case the eggs remain in the water, the process is even faster. The larva feeds on bacteria and takes four to eight days to develop into a pupa. Larvae can survive for months at a cold temperature. The pupal stage lasts from two to three days, after which an adult mosquito emerges.
Preparing to fight back
There are several actions in course focusing on either the mosquito or the viruses. According to the World Health Organization (WHO), fifteen research groups are currently working on the development of vaccines for the viruses, but they estimate at least eighteen months before large-scale testing.
Other actions have as target the elimination of the mosquito. The Brazilian government is running a campaign for the removal of the stagnant water involving several sectors of the society. Its plan is to hinder the mosquito reproduction. The government is also using fogging as an emergency local measure at dusk and down.
Scientists tried the release of radiation-sterilized males of A. aegypti. Those males do mate but produce no viable eggs. The problem with this technique was that the resulting males were too weak. In another attempt, researchers released transgenic males, whose offspring do not survive larval stage. Although the latter procedure was efficient, it is very expensive.
A promising alternative is the use of the bacterium of the genus Wolbachia. This bacterium is naturally present in 60% of common insects and has no effect on humans. When present in A. aegypti, the bacteria can either reduce the ability of mosquitoes to transmit the virus or prevent their eggs from hatching, depending on the strain used. Other countries reported encouraging results using this strategy against Zika, Chikungunya, and Dengue viruses. In Brazil, tests are under way in Rio de Janeiro and Niterói.
This article does not intend to scare you away from the games, but to give you a real panorama of the situation in Brazil. In case you decide to come, I recommend three simple measures to protect yourself:
Use insect repellents all the time.
Use light clothes that cover most of your body (long sleeves, trousers).
Consult a doctor in case you feel the symptoms reported here.
Apart from that, enjoy your stay and try to keep yourself informed. Research institutions and universities always bring new information to the scene. Who knows what can happen in the meantime?
Most sources I used in my research were in Portuguese, such as interviews with specialists and Brazilian authorities. I don’t think it is worth listing them all. For further information, I suggest three websites that could be included in the end of the article if you like. As I don’t know your policy about citing other sites, I listed them below.
– World Health Organization: http://www.who.int/en/
– The public health institution Instituto Oswaldo Cruz: http://portal.fiocruz.br/en/content/home-ingl%C3%AAs
– Brazilian Ministry of Health (in Portuguese): http://portalsaude.saude.gov.br/