Zika virus isn't the only concern for Rio Olympics

What will the Zika virus outbreak mean for Olympic athletes bound for the 2016 Rio Olympics? While there is a risk, athletes should be more concerned about dengue and other infections.

It’s not just pregnant women who are anxious about the explosive spread of Zika virus in Brazil; so too are Olympic athletes. And unlike pregnant women, Olympic athletes, who have what might be a once in a lifetime opportunity to compete at the highest level of their sport, aren’t likely to postpone traveling to Brazil. But is Zika what they really need to be worried about?

Athletes competing in the 2016 Olympics in Rio, female or male, should be far more concerned about dengue than its cousin Zika. Before Zika and its cousin chikungunya hit Brazil, researchers examined the records of travelers to Brazil between 1997 and 2013 and found that the most common diseases contracted there were dengue, skin conditions and diarrheal illnesses. Dengue and malaria were the most common severe illnesses requiring hospitalization. With the exception of five fútbol stadiums, all Olympic venues are in Rio de Janeiro, where there’s no risk of malaria or Yellow Fever.

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Dengue is found throughout Brazil and is also mosquito-borne. In contrast to Zika, which often infects without causing symptoms, adults who get dengue usually get sick. Symptoms of dengue include fever, headaches and rash. Dengue also causes severe muscle and joint pain, which has earned it the monikers “break-bone fever,” “bone-crusher disease” and “dandy fever,” this last for the contorted postures and gait it caused among slaves in the West Indies. Dengue may also cause a hemorrhagic fever, not unlike Ebola, with spontaneous bruising and bleeding. A bedside test depends on bruising to diagnose dengue hemorrhagic fever: in the right context, if you develop red splotches on your arm after applying a tourniquet or blood pressure cuff, you probably have dengue.

Like Ebola, dengue can cause your blood vessels to become leaky and your blood pressure to plunge dangerously. And like its cousins Zika and chikungunya, dengue seems very rarely to cause Guillain-Barré syndrome, a progressive though usually temporary paralysis that moves from the feet and hands towards the torso, eventually leaving some victims unable to breathe on their own. One in 100 dengue victims will die of the disease.

The worst cases of dengue usually occur not the first time you’re infected, but the second time. When you get dengue, or any infection, your immune system learns to produce antibodies, which stick to the infecting microbe, trap it, and alert the rest of the immune system to its presence. After you recover, your immune system keeps a small stockpile of antibodies against the microbes it’s encountered so that it can attack more quickly the next time around. Then if your immune system again encounters dengue, it already has some antibodies around to help fight it off; except that your antibodies can function as a Trojan horse of sorts and flare the flames of the dengue virus infection.

AP Photo/Andre Penner

It’s not that Zika virus isn’t a concern—it could well put an athlete at a real disadvantage. But the real risk is to women who are or are trying to get pregnant; the U. S. Centers for Disease Control and Prevention (CDC) is recommending that these women postpone traveling to Zika-transmission zones until after their pregnancy. If a woman who’s not pregnant gets Zika and recovers, she can safely get pregnant and have a baby afterwards; however, she should wait at least one month after recovery before trying to get pregnant.

It’s rare, though not unheard of, for Olympic athletes to compete while pregnant. Take, for instance, Kerri Walsh Jennings, who was five weeks pregnant when she won the gold medal at the 2012 Summer Olympics. But it’s far more common for elite female athletes to have irregular periods or to stop menstruating completely, making it more difficult to get pregnant. At the same time, if they have irregular periods, women may not realize they’re pregnant until later since they can’t count on a missed period to alert them. Some female athletes are reluctant to use hormonal contraceptives like the pill because they’re worried the estrogen or progesterone could compromise their athletic performance. Hormone-free copper intra-uterine devices are highly effective in preventing pregnancy. And for some women, the benefits of hormonal contraceptives (e.g. lighter periods) may outweigh any possible (though as yet unproven) impact on performance.

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Dengue’s milder cousins chikungunya didn’t strike Brazil until 2014, and Zika not until the following year—all transmitted by the Aedes aegypti mosquito. These three viruses are known for causing fever, rash and joint pain, which could be handicaps to any Olympic athlete. The good news is that measures to protect against mosquitoes will protect against all three of these viruses as well as malaria and Yellow Fever, including loose-fitting long-sleeved shirts and pants; spraying with DEET-containing insect repellent; treating clothes and gear with permethrin; sleeping under a bed net and staying indoors where it’s screened-in or air-conditioned as much as possible. It’s also important to note that the Olympics will take place in August, the low season for dengue transmission in Brazil.

After dengue, the most common infection among those returning from Brazil is cutaneous larva migrans from dog or cat hookworm. Cutaneous larva migrans causes intense itching and worm-like reddish brown tracks under the skin where the worms are migrating. You get cutaneous larva migrans from walking barefoot on the beach or sitting on sand. While not life-threatening, it would be maddening to compete with creepy crawlies under your skin.

There’s always a risk of diarrhea when we travel. Sometimes it’s just the change in our diets or stress, but sometimes it’s something more. Travelers, especially single ones, are also more likely to engage in unprotected sex. So they’re at risk for sexually-transmitted infections, which may now also include the Zika virus. I take care of HIV-infected patients in New York City, and I know of at least one who was infected while attending the 2010 World Cup in South Africa.

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Mass gatherings increase the risk of infectious disease transmission, whether it’s influenza at the Super Bowl, norovirus at the 2006 World Cup, or meningitis at the Hajj. It will be winter and flu season in Brazil in August, but the influenza vaccination used in the U. S. won’t necessarily protect you against strains in Brazil. The southern hemisphere version of the vaccine would be best, but a recent flu shot at home is still better than nothing. The flu isn’t sneezing and runny nose; it’s fevers, body aches, nausea and vomiting.

It’s not just travelers to Brazil who are at risk. Zika may have been brought to Brazil during the 2014 World Cup, and the country remains at risk for importation of other mosquito-borne diseases.

Some have called for cancellation of the Rio Olympics—this is alarmist and sends the wrong message. The Ebola outbreak had a “crippling” impact on the economies of Guinea, Liberia and Sierra Leone, not least because of disruptions in travel and cross-border trade as well as decreased foreign investment. Even in the case of Ebola, travel bans were unjustified and could well have backfired.

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For the vast majority playing in and attending the Games, Zika is not a significant public health threat. They should be more worried about dengue, influenza and sexually transmitted infections, none of which are new.

Cancelling the Olympics is not a pragmatic solution. It’s like saying women should just stop having sex so as not to have a baby with microcephaly, in essence what countries like El Salvador are advising. It’s simplistic to say, ”better safe than sorry.”  Public health recommendations won’t work if they aren’t realistic and aren’t followed.

The most important thing Olympic athletes—and for that matter anyone traveling out of the country—can do is to go to a Travel Medicine Clinic before they leave. Unfortunately only about half—at best—seek out this advice. Whether you’re an Olympic athlete or a fan traveling to Brazil in August, you should see a doctor, who can tailor recommendations based on your medical history and exactly where you’ll be going.

Celine Gounder, MD, ScM is an internist, infectious diseases and public health specialist and medical journalist. Follow her on Twitter @CelineGounder.