With the Olympic and Paralympic Games imminent, the Zika virus (ZIKV) outbreak in South and Central America has led to worries about participant and spectator safety. ZIKV outbreaks have historically occurred in tropical Africa, Southeast Asia, the South Pacific, the Americas, and the Caribbean with the latest outbreak occurring in 20 regions of South America including Brazil where Rio de Janeiro is the nation’s second hardest-hit region (3,14). Concerns have been raised by the World Health Organization (WHO), the U.S. Centers for Disease Control (CDC), as well as the National Olympic and Paralympic Committees, International Sport Federations, athletes, families, and spectators. The WHO declared ZIKV a “public health emergency of international concern” in February 2016 (13), while the CDC has issued an alert to travelers to Brazil, recommending that all persons traveling to Brazil practice enhanced preventive measures (2,10). These warnings have led to a number of nations and athletes to consider possibly withdrawing from the games.
ZIKV is an arthropod-borne virus (arbovirus) first discovered in the Zika forest of Uganda in 1947 (1). ZIKV is mainly transmitted via a bite from a female mosquito of the Aedes species. (Aedes aegypti and Aedes albopictus) (1). These are the same mosquitoes that transmit dengue virus and yellow fever. Aedes mosquitoes prefer to bite people and are aggressive daytime feeders who also favor living indoors where they have better access to humans. Mosquitoes become infected when they feed on a person who is already infected and can then transmit the virus to the next person they feed upon. The greatest time of transmission from mosquito to human is during the first week of infection with ZIKV.
There also are several modes of human-to-human transmission. ZIKV also has been detected in semen (ZIKV remains present in semen longer than it does in blood), and sexual transmission from an infected male partner has been reported (7). Furthermore, maternal-fetal transmission can occur vertically as well as during childbirth. Because it is a bloodborne disease, ZIKV also can be transmitted through blood transfusions.
During Brazil’s summer season (December to March), mosquitoes rapidly breed and their numbers increase exponentially, which maximizes the risk of disease. However, the Olympic and Paralympic games will occur in August, which is the cooler, drier season in Brazil. This climactic shift will reduce the total number of mosquitoes and may reduce the risk of viral transmission.
Most people that become infected with ZIKV will be unaware of the infection because many will not exhibit symptoms. Less than 20% of those infected will develop symptoms, which are nonspecific and include fever, conjunctivitis, headache, maculopapular rash, malaise, myalgia, and arthralgia (1). The symptoms are usually mild and last for up to a week. The differential diagnosis for these symptoms is broad and includes other viral infectious (e.g., herpes simplex, cytomegalovirus, Epstein-Barr, rubella, measles, and HIV), malaria, and group A Streptococcus infections. In highly trained athletes, symptoms of Zika infection might be mistaken for micronutrient imbalance, fatigue, and overtraining syndrome, which can further complicate diagnosis.
Preferred diagnosis is based on real-time reverse-transcription polymerase chain reaction (rRT-PCR) from blood and urine, which is currently available only on limited capacity (5,12). The CDC recommends serum and urine rRT-PCR testing within 1 and 2 wk of symptom onset, respectively (5). Serum antibody-based laboratory tests are not yet fully reliable as many also have cross-reactivity with previous dengue infection and yellow fever vaccination (10).
Currently, there is no specific antiviral treatment or vaccine for Zika infection, and disease control is limited to preventing mosquito bites and eradicating the mosquitoes (7,10,12). Vaccine development is in progress, but it is unlikely that a viable vaccine will be available before the Rio Games (4). Those individuals who exhibit the nonspecific symptoms of possible ZIKV infection are advised to get plenty of rest, drink fluids to prevent dehydration, and treat their symptoms. Acetaminophen is recommended as the medication of choice to reduce fever and pain as aspirin and nonsteroidal anti-inflammatory drugs may increase bleeding risk, if the nonspecific symptoms are actually from dengue virus (2).
Because there is no treatment for ZIKV infection, current advice to athletes and travelers is focused on personal protection and preventive measures. Minimizing or eliminating standing or stagnant water will significantly reduce areas for mosquito breeding and will reduce the mosquito vector load. Because the A. aegypti mosquito flies low with a preference for biting humans during daytime and prefers to live indoors, it is recommended that athletes and spectators use approved mosquito repellents and cover exposed skin by wearing closed shoes, long loose pants, long-sleeved shirts, and hats thick enough to block a mosquito bite during the daytime (2,13,14). In sports with limited body cover such as wrestling and aquatic sports, particularly in open water swimming, use of appropriate mosquito repellents on all exposed skin is essential.
Living accommodations and indoor sporting venues should have appropriate window and door coverings/screens to prevent mosquito entry and should be air-conditioned to maintain comfortable indoor temperature without the need to open doors or windows. An air-lock design with negative pressure air to outside at entry of indoor venues may further limit mosquito ingress to large indoor facilities.
There is evidence to support possible correlation between Zika infection and congenital microcephaly in infants of infected mothers (1,10,12). According to the CDC, pregnant women who have traveled to affected regions should be considered for serologic testing 2 to 12 wk after their return regardless of absence of symptoms (2,8). Women returning from these areas are advised to avoid pregnancy for at least 8 wk even if fully asymptomatic. Men who have traveled to an area with known ZIKV are advised to use condoms for 8 wk to protect their sexual partners (10). Although the Brazilian Ministry of Health also has reported an increase in cases of Guillain-Barre syndrome (GBS), there is currently no strong evidence to support a linkage between a recent upsurge in cases of GBS in South America and the Zika outbreak (8,9).
Another special concern is the introduction of infection to the mosquito population in countries of the Northern Hemisphere by athletes, athlete support personnel, and visitors returning from Brazil. Although the Olympic Games will be held in August during the cooler and drier climate of Brazil’s winter, reducing Brazil’s mosquito density, spectators will return to the Northern Hemisphere’s late summer where the mosquito population will be at its peak, increasing the risk that uninfected mosquitoes will feed on infected travelers and then transmit disease. Because of this, returning travelers are advised to continue mosquito preventive efforts for 3 wk to ensure that ZIKV is not transmitted to uninfected mosquitoes.
To mitigate the risk of ZIKV transmission at the games, the Brazilian government is deploying more than 200,000 personnel to help educate the population and assist them by cleaning areas of stagnant water to reduce mosquito breeding grounds. The International Olympic Committee and Brazilian officials are confident in the safety and success of the Games, and have set a plan for regular inspection of venues and water quality during the games (6). Furthermore, the United States Olympic Committee has organized an Infectious Disease Advisory Group to identify best practices that will prepare and protect athletes and staff attending the games (11).
The increase in ZIKV-infected mosquitoes in South America and the mass influx of people to Brazil during the games has the potential to create a large-scale public health problem. Because there is no vaccine or treatment for ZIKV, preventive efforts are the best “treatment” to reduce the risk of infection. There are special concerns for women of reproductive age who are pregnant or planning to becoming pregnant, with the potential for birth defects and risk of vertical transmission. Furthermore, the possibility of Zika spread by returning travelers highlights the need for mosquito safety and enhanced prevention efforts for those who travel as well as those who stay home. With the appropriate prevention and protective efforts, we can ensure that our athletes remain “faster, higher, stronger” safely.
ZIKV is transmitted by the bite of the Aedes mosquito
Signs and symptoms of ZIKV are nonspecific and may mimic many other disease conditions
There is no vaccine or treatment for ZIKV
Women of reproductive age should be counseled regarding the risks of travel to South America
Insect repellent, proper clothing, and avoidance of areas with stagnant water are the best preventive efforts
Returning travelers should continue mosquito prevention efforts for 3 wk
Women and men with possible ZIKV exposure with or without clinical symptoms should avoid conception for at least 8 wk after exposure
The authors declare no conflict of interest and do not have any financial disclosures.
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