Caption: Aedes Aegypti enjoying a tasty meal
Photo credit: National Science Foundation
There has been much hysteria in the news recently about the rapid spread of the Zika virus disease (ZVD). Awareness has been heightened by the 2016 summer Olympic games in Rio de Janeiro, where the epidemic is widespread and a number of athletes withdrew due to fears of contracting an infection. Unfortunately for surfers, the disease seems to have a predilection for locales with great surf in Central America, South America, and the Caribbean. Particularly hard hit are Brazil, Puerto Rico, Panama and El Salvador. This article will explore Zika, with an eye towards the travelling surfer as well as touch upon the closely related diseases of Dengue and Chikungunya.
History
Zika was first isolated from a monkey in the jungles of Uganda in 1945 and later identified as a single-stranded RNA flavivirus transmitted by the Aedes Aegypti mosquito. The virus was restricted to the African and Asian continents until 2007 when it was first noted to have crossed the Atlantic, leading to an epidemic which broke out in Brazil in 2015 and rapidly spread north through Central America and into Mexico and south into Argentina. In 2016, cases of active transmission were noted in Florida, and Zika is expected to spread to other states in the southern half of the US. Concern regarding the spread of the disease was significantly heightened when a spike in the number of Brazilian babies born with microcephaly was linked to Zika infections in pregnant mothers. 
Spread
Transmission occurs via the bite of an infected female mosquito A. Aegypti (or its closely related cousins; A. africanus, A. albobticus, A. furcifer, A. hensilli). It should be noted that Aedes is also the major vector for Dengue and Chikengunya, so these diseases often coexist in a single geographic location. Female mosquitos require a mammalian blood meal during their short lifespans and lay eggs in stagnant fresh water. Unlike the vector for Malaria, Anopheles, which feeds primarily at night, A. Aegypti is a diurnal feeder. Furthermore, it thrives in heavily populated urban environments because it prefers to lay eggs in artificial water containers and only needs a bottle-cap full of water to reproduce. These facts, combined with the increased frequency of international travel are likely to account for the rapid proliferation of ZVD in urban areas. Epidemics in Yap, Micronesia (2007) and in Tahiti (2013) spread through the local population quickly, with infection rates as high as 75%.
Unlike most other mosquito-borne illnesses, ZVD can also be spread via sexual contact. Zika virus has been detected in semen for at least 12 weeks post infection, and transmission via vaginal, oral and anal sex have been well documented. This has particularly serious implications given that ZVD is known to cause birth defects. The CDC currently recommends that men who have contracted ZVD or travelled from endemic areas wear condoms during sexual intercourse to avoid transmission to their partners. Zika is also present in saliva, but as of this writing there have been no confirmed cases of the disease being spread through saliva.
Symptoms and Complications
For all the hype surrounding the disease, the symptoms of Zika are fairly innocuous. In fact, as many as 70% of those infected by the virus are completely asymptomatic, and most people develop only a low grade fever, a rash (See Fig 3), conjunctivitis and minor myalgias. 
Headaches, arthralgias and oral sores are other less common symptoms. The the course is usually benign, and symptoms generally resolve within several days to a week. No deaths related to the disease have been reported.
The major complications of the disease are Guillain-Barre syndrome (GBS) and neurologic birth defects of children born to mothers who became infected with ZVD during pregnancy. During the epidemic in Tahiti, the incidence of GBS increased from a baseline of 7 cases per year, to 42 cases during the peak of the epidemic. A similar spike in incidence has been seen in Brazil. The most feared complication and the most relevant for surfers is an increase in the risk of microcephaly and other neural fetal defects seen in babies born to mothers who have contracted ZVD while pregnant. The risk is high enough so that the Centers for Disease Control (CDC) recommends that pregnant women living in areas free of Zika not travel to countries where there is active transmission of ZVD. (see map above)
Treatment
Treatment is entirely supportive. Rest, adequate hydration and control of fever with Acetaminophen is usually sufficient. NSAIDS should be avoided. No vaccine exists, though one is in development.
The Differential Diagnosis: Dengue and Chikungunya
Unless you are a woman who is pregnant or wants to get pregnant, or a guy who wants to have a child, there is no particular reason not to travel to an area afflicted with Zika. Indeed, all the hype may work in your favor by lowering lodging rates and making for less crowded surf-breaks. However, the more serious illness of Dengue and Chikungunya are another issue. All three diseases are carried by the same mosquito, so the geographic distributions of these diseases is similar, and to complicate matters all three diseases have overlapping symptoms.
Dengue, a.k.a. “break bone fever” just like Zika, is a Falvivirus carried by Aedes mosquitos. It is currently more widespread than Zika (see Fig 4) and can be fatal. The typical symptoms of Dengue include high fevers, severe myalgias and arthralgias, headaches, and a blanching rash which has been described in its later stages as “islands of white in a sea of red”. Fevers are generally sudden onset, accompanied by a retro-orbital headache and spike 3-14 days after inoculation. Fevers are typically bi-phasic, disappearing after 2 or 3 days, then reappearing 5 days after symptom onset. It is not uncommon for malaise to persist for weeks. Children often experience vomiting and diarrhea, which is uncommon in adults. 
Hemorrhagic fever and shock are rare but feared complications, occurring in less than 2% of cases. This only appears to occur when a patient previously infected by one of four strains of Dengue, is later infected by another strain of the disease causing an overwhelming immune response. These patient, often children living in endemic areas, develop severe thrombocytopenia, leukopenia and third spacing of fluids due to capillary leak.
There is no vaccination or cure for Dengue. Treatment is supportive with hydration, rest, and fever control with Acetaminophen. Aspirin and other NSAIDS should be avoided due to bleeding complications. Any signs of bleeding from mucous membranes, petechiae, or shock should prompt a visit to the hospital, but most can safely let the disease run its course. Thrombocytopenia and leukopenia are common lab abnormalities. The tourniquet test may be useful in making the diagnosis in areas where laboratory testing is limited. This test involves inflating a blood pressure cuff on the patients arm to between systolic and diastolic pressure and leaving it on for 5 minutes. More than 10 – 20 petechial hemorrhages per square inch (2.5 cm2) make the diagnosis of Dengue likely.
Chikungunya
Chikungunya is another mosquito-borne viral disease with a strange name emerging from the depths of the African forest. First described in Tanzania in the early 1950’s, Chikungunya first appeared outside of Africa during an outbreak in Thailand in 1956, and rapidly spread to tropical locations around the world. After a period of quiescence in the ‘90’s there has been a resurgence of disease with outbreaks in Mexico, Indo, El Salvador, St. Maarten and numerous islands in the South Pacific, with very high attack rates in previously unexposed populations. An updated list of countries currently affected by the disease can be found here.
Chikungunya, like Dengue causes high fevers lasting a few days, and a rash, but is accompanied by much more severe and often debilitating arthralgias which last for weeks to months. Headaches, fatigue, and nausea are also common. Fevers are usually above 39o F and are often biphasic, breaking and then returning a few days later. Joint pains, appearing 3-4 days after onset of fevers, are reported in 90% of cases and are usually in the smaller peripheral joints of the upper and lower extremities such as elbows, wrists, fingers, and ankles. Multiple joints are usually affected in a symmetric distribution. A maculopapular rash similar to that seen in Zika occurs 2-5 days after the onset of symptoms in 40 – 50 % of cases.
While GBS has been reported as a complication of Chikungunya, hemorrhagic fevers are extremely rare. Chronic fatigue and long term disability, however, are very common. During the 2006 outbreak in Reunion Island (famous for its good surf and bad sharks) over half of the people affected by the disease suffered from joint pains three years following the initial infection. Like Zika and Dengue, Thrombocytopenia, leukopenia, and elevated liver function tests are common. The mortality rate is approximately 1:1,000 cases.
Prevention
Because there are currently no effective vaccines or cures for Zika, Dengue, or Chikungunya, avoidance of mosquito bites is key. The usual surfer’s remedy of waving one’s hands frantically in the air when you hear an annoying buzzing sound near your head has been well studied and proven ineffective. DEET 25% (or higher) applied every 8 hours is time tested and continues to be recommended by the CDC for the prevention of mosquito bites. Though DEET is absorbed systemically, it has a long track record of safety, and is considered safe during pregnancy. However, the smell is unpleasant, the chemical is oily, and it dissolves plastics, so it can ruin your tent, back-pack or shell. Far more pleasant, and equally effective as DEET, is Picaridin (aka Icaridin), a naturally occurring chemical found in pepper plants. Picaridin has a faint and pleasant odor, is less oily than DEET, and does not dissolve plastics. It should be used as a 20% concentration. Oil of Eucalyptus, another naturally occurring oil is less effective and shorter lasting than the other repellants.
Wearing long-sleeved shirts, long pants and hat is also effective, though may be impractical in steamy-hot climates. Treating one’s clothes with the insecticide Permethrin is another effective and inexpensive way to avoid mosquito bites and also protects against ticks. When sleeping in the tropics, using a bed net which has been treated with Permethrin, and paying a few extra pesos to sleeping in air-conditioned quarters where the windows can be closed at night is worth the money where zika, dengue, or chikungunya are endemic.
Surfer-girls who are pregnant or wish to become pregnant should take extra-special precautions if living in areas where Zika is prevalent, and avoid travelling to those areas if possible. Men who are infected with ZVD, and perhaps men living in or travelling from these areas should wear condoms during sexual intercourse for six months after contracting ZVD to avoid pregnancy and the possible complication of microcephaly.