As stories about Zika and other mosquito-borne illnesses make the news, Kent State experts prepare students to deal with future outbreaks—and share facts to help calm your fears.
By Beth Skwarecki
Zika. Dengue. West Nile. Malaria. When diseases like these hit the headlines, attention turns to the ferocious creature causing these outbreaks that threaten human health—the lowly mosquito.
Amy Krystosik, PhD ’16, an epidemiologist and former graduate assistant in Kent State’s College of Public Health, spent six months in 2015 and 2016 stalking this six-legged menace in Cali, Colombia, a tiny camera tucked in her hand. Krystosik and her guide for the day—usually the municipal secretary of health or a concerned citizen who wanted to fill her in on what was going on in the neighborhood—would meet in the early hours of the morning, the safest time to be in some of the notoriously violent areas she was surveying.
With video, audio and Global Positioning System (GPS) technology running, they collected data on mosquito-borne diseases by simply chatting about what they observed as they walked through the neighborhoods, recording what they saw: waterlogged garbage here, an open canal there. Baby mosquitoes go through a tadpole-like aquatic stage before they are old enough to fly, so the more standing water, the more likely disease-carrying mosquitoes call the area home.
But that’s not all Krystosik and her colleagues were looking for. Other data points worth collecting were signs of high rates of homelessness and poverty. After all, a person with limited access to shelter and clothing is at a higher risk of being bitten than someone who can easily afford bug repellent and window screens. By strolling the streets of Cali, Krystosik was collecting a richer picture of the area’s mosquito borne-disease problems (chikungunya, dengue and Zika) than she got from charts of numbers.
The information she gathered as part of her doctoral research helped mobilize local resources to improve control of outbreaks in the field, create local risk maps and uncover trends that will be useful for future infectious disease control programs.
The Danger of Mosquitoes
Mosquito-borne diseases are deadly enough that Bill Gates, whose foundation fights malaria and more, calculated that the tiny insect kills more people each year—750,000 annually—than any other animal. (Humans come in second place, followed distantly by snakes, dogs, and another disease-carrying insect, the tsetse fly.)
Without mosquitoes, there would be no mosquito-borne diseases. But of the world’s approximately 3,500 mosquito species, only a handful actually spread disease to humans. And eliminating mosquitoes worldwide isn’t a realistic solution.
Of the world’s approximately 3,500 mosquito species, only a handful actually spread disease to humans.
“We tried to eliminate malaria [that way] and failed,” says Madhav Bhatta, PhD, an associate professor in the College of Public Health, who also serves as a consultant epidemiologist in public health emergency preparedness for Tuscarawas county. The cornerstone of that effort was widespread use of DDT, which killed mosquitoes—but also other insects.
Even modern insecticides can have unfortunate results. When Dorchester County in South Carolina used an airplane to spray for mosquitoes in July 2016, farmers found piles of dead bees in their fields. “There will always be unintended consequences of any chemically based control measures,” says Bhatta.
Spraying pesticides is still one prong of public health efforts against mosquito-borne disease, but it is usually targeted to specific areas with mosquito breeding sites. Another important way to prevent these diseases is convincing people to avoid contact with mosquitoes, which includes spraying themselves with insect repellents and using barriers like long-sleeved clothing, bed nets and window screens.
Worldwide, malaria is the biggest mosquito-borne threat: it’s responsible for the deaths of more than 600,000 people every year. Malaria travels in the tiny bodies of Anopheles mosquitoes that live in tropical areas around the globe. Meanwhile, the Culex mosquitoes that are common throughout the United States are less dangerous, but not entirely blame free: they can carry West Nile virus and St. Louis encephalitis.
Lately, though, the most newsworthy mosquito is Aedes aegypti, which transmits some serious diseases in tropical parts of the world. Dengue, chikungunya, and yellow fever have long been its specialties. And recently, this multitalented mosquito has been making headlines over a formerly obscure part of its repertoire: Zika virus, the one that causes babies to be born with neurological problems and small heads.
A New Threat
Zika is not a new disease, but it was only in 2015 that Brazilian doctors and public health officials suspected it was correlated with a sudden surge in cases of microcephaly. Babies born to Zika-infected mothers often had smaller than usual heads. Many of those infants turned out to have other problems as well. Impaired vision and hearing, developmental delays such as trouble walking and seizures are among the symptoms that babies born with Zika may face as they mature.
Aside from those birth defects, Zika hasn’t shown itself to be a particularly dangerous disease. Some 80 percent of people who are infected never show it. In those who do, a case might be no worse than a rash and some flu-like symptoms. Avoiding Zika-carrying mosquitoes is crucial for pregnant women and their partners (since it can also spread sexually), but other people have little to fear.
Fear takes over, though, in many people’s minds. In a 2016 survey by the Annenberg Public Policy Center, 42 percent of Americans said that a person infected with Zika is “very likely” or “somewhat likely” to die. That’s just not true.
In a 2016 survey, 42 percent of Americans said that a person infected with Zika is “very likely” or “somewhat likely” to die. That’s just not true.
Tara Smith, PhD, associate professor of epidemiology in the College of Public Health, was one of just a few people who recognized the name Zika when the outbreak started making headlines in early 2016. “At that point, there were few people for reporters to talk to,” she says. Smith noticed people asking questions about the virus, sometimes assuming the worst. So she penned a few articles—one for Mental Floss, another for Quartz and several more since—calmly laying out the facts.
Smith relayed how the disease is and is not transmitted, and she explained that the Centers for Disease Control and Prevention (CDC) advises pregnant women not to travel to countries where Zika is spreading. She gave a reality check on the chances that Zika could come northward to the United States—possible, but unlikely to spread widely.
Communicating well about diseases like Zika is tricky. The CDC wants you to fear Zika just enough that you cancel your travel plans to Zika zones if you are pregnant, and that pregnant women and their partners use effective mosquito repellents if they can’t avoid one of those areas.
Since the Zika virus remains viable in both male and female body fluids for at least several weeks, the CDC currently recommends that people who have been to an area with Zika, even if they show no symptoms, take precautions with sexual partners for up to six months after their return. (See www.cdc.gov/zika/ for updates.)
When fear takes over, however, rumors may fly that a disease is deadly when it is not, or that it is a fiction created as part of a government cover-up. Those are some of the theories Smith found herself having to debunk online.
The bottom line, says Smith: Don’t panic. “We saw it with Ebola, we saw it with Zika, that people listen to the news and they get scared.” In early 2016, the World Health Organization declared the South American Zika outbreak an international public health emergency. That sounded scary, but it didn’t mean that the disease is a threat to everyone in the world. Instead, the designation spurred countries to divert money to prevention and treatment efforts.
The truth is, for someone in a place like Ohio, Zika is unlikely to be an immediate threat. While the virus can spread in warm climates where the mosquito already lives, like Florida and Texas, even those areas are not likely to see the kind of spread or the frequency of birth defects as the South American countries where the outbreak hit first.
“We have good health care systems here,” Smith says. “We have good prevention systems here.” Far fewer buildings lack window screens, for one thing. We also don’t have dense populations of mosquitoes living in the same place as dense populations of people, like those Krystosik saw in Colombia.
But that doesn’t mean Ohio is off the hook. Christopher Woolverton, PhD, professor of biostatistics, environmental health sciences and epidemiology in the College of Public Health and former Kent City Board of Health president, has watched the state’s approach to mosquito-borne disease shift over the years. West Nile virus was new and scary in the early 2000s, and public health researchers began catching mosquitoes in traps (small boxes placed near areas of standing water) and testing them for the virus.
When concern about West Nile died down, federal and state governments stopped funding this surveillance. (Some municipalities, including Kent, found the funding to keep doing it.) “But now that Zika is in the spotlight, the trapping and testing are making a comeback,” says Woolverton. “However, we still teach and practice prevention over paranoia.”
Ohio lies at the edge of Aedes mosquito range. The mosquito spreading Zika in South America is a species called Aedes aegypti, and its relative Aedes albopictus has been spotted in southern Ohio. With traps all over the state, public health officials can tell when, where and if the mosquito begins to spread. This system, developed for West Nile, is ready to keep an eye out for Zika-carrying mosquitoes, too.
Building on the Past
Zika is brand new as a public health concern. But since it is a close relative of several other viruses that scientists and doctors know all too well, past efforts to thwart those other diseases can be quickly turned to monitoring and addressing the new one.
Vaccines for Zika’s relative, dengue fever, for example, have been under development since the 1940s, and the first one was only just licensed in 2015. But scientists were able to develop an experimental vaccine for Zika in record time, coming up with a vaccine to test in just a few short months, which recent news reports say could be available as early as 2018. Blood tests for Zika also built on previous work: its genetic material is similar to that of dengue and other relatives.
The camera/GPS technology that Krystosik used to map Zika hazards in Cali, Colombia, was already in place, as well. She had originally planned to work on a different project with the Causaseco research institute there, testing whether insecticide-laced sugar could kill enough mosquitoes to be effective against malaria. But when she couldn’t travel safely to the malaria-stricken areas and needed an alternate plan, she remembered that she had heard Andrew Curtis speak about a new way of mapping out the risks of a neighborhood.
Andrew Curtis, PhD—who came to Kent State in 2012 and is a professor of geography and the current co-director of the GIS, Health & Hazards Lab—was an assistant professor at Louisiana State University when Hurricane Katrina hit in 2005. Part of a team that supported operations in the state’s Emergency Operation Center during the response to Katrina, Curtis came up with a spatial video system to survey the damage on a hyper-local level.
Cameras fastened to an SUV were connected to a central global positioning system, and Curtis and his students went street by street, video mapping the neighborhoods hit hardest by Katrina. Members of the community rode along to talk about what had been there and what was lost. The team created maps and gave them back to the neighborhoods to help with planning and grant applications, Curtis says. Teams have returned to New Orleans over the years to document the remaining devastation and the rebuilding process.
Since then, this walk-and-talk approach has allowed researchers to collect data on gang violence and homelessness in American cities, cholera risks in Haiti and more.
“We map challenging spaces,” says Curtis, whose projects target places where official data is lacking and where societal problems like poverty are layered with health issues. In one project, a student from his team at Kent State carried a video camera in a rowboat to get a better view of a slum on a lake in Bangladesh.
There’s just no substitute for seeing the neighborhoods for yourself. A group of Kent State public health students also learned the value of firsthand observation when their annual trip brought them to Brazil in the midst of the recent Zika epidemic in spring 2016.
Mark James, PhD, professor and chair of the Department of Biostatistics, Environmental Health Sciences and Epidemiology and executive director of Global Health Programs for the College of Public Health, leads public health students on a trip every year to visit partner institutions in different parts of the world. The 2016 trip went to the Oswaldo Cruz Institute in Rio de Janeiro. At first, their experience included lectures at the institute on everything from leprosy to Zika to cardiovascular diseases. Shortly afterward, in Manaus, the students followed community health workers making their rounds on motor scooters.
A family had hung a red flag outside their house, the signal that somebody inside was suffering from a fever. The health workers stopped there and took blood from three people to examine for malaria parasites.
The students also saw mosquito habitats up close, from forgotten old tires to community ponds that were popular among residents as areas to bathe in and have fun. “You can read about things in a textbook or hear people talking about it in lectures,” James says, “but nothing compares to seeing it in real life.”
Keeping Mosquito-Borne Disease in Check
The College of Public Health’s Brazil study abroad course took place in May, as the southern hemisphere’s summer was ending. Zika cases were already declining, and the students didn’t see many mosquitoes. But they definitely came prepared.
James and the students went over the CDC-recommended prevention guidelines—wear long sleeves and pants, use DEET-containing repellents and stick to air-conditioned indoor places as much as possible—and the excursion went without a hitch, James says. “Everybody was diligent about putting on their insect repellant.”
Those are the same recommendations the CDC gives to pregnant women, although they obviously have more at stake. DEET, the main ingredient in highly effective repellents, is safe to apply in pregnancy. If you’re only afraid of a few itchy bites on a camping trip, you might get lazy with the repellent. But when your baby could suffer birth defects, or if you are at risk for a dangerous mosquito-borne disease like malaria, even a single bite can be disastrous. Less effective means of avoiding bites, like the citronella candles so many of us bring out at summertime barbecues, don’t cut it when your health is at stake (see box below).
The Next Pandemic
The public health emergency around Zika was declared to be over in November 2016. The virus is still out there, but public health officials are now treating it as a simmering presence, not a sudden explosive threat. And scientists are keeping an eye out for the next disease to catch the world by surprise.
“We are going to keep seeing these pandemics, keep seeing these epidemics,” says Smith, because so many viruses and other pathogens are already out there, under our radar. Many, like Ebola, infected animals before making a jump to humans. And even Zika kept to itself for decades after its discovery, quietly infecting people in a few Pacific island nations before suddenly causing a rash of Brazilian microcephaly cases.
“What are the pressures that cause [diseases] to suddenly erupt after being fairly silent for the maybe 50 years that we’ve known about them?” Smith asks. “I don’t think we know, and that limits our ability to predict what is next.”
One exciting possibility, Woolverton notes, is an effort by several international teams to create a vaccine for an entire broad family of viruses that haven’t yet become a problem. Then, if any virus in that family sparks an outbreak, scientists could quickly tweak the vaccine and be ready to go. “It sounds a little sci-fi-ish, but the science is sound,” he says.
Such a plan would need massive amounts of funding, so it may never happen. But experts at Kent State and beyond are convinced that new pandemics are on the horizon. Growing mosquito populations, thanks to climate change, mean another mosquito-borne disease may well be the next threat.
Beth Skwarecki is a health and science writer based in Pittsburgh, Pennsylvania. Her book, Outbreak!: 50 Tales of Epidemics that Terrorized the World (Adams Media) was published in October 2016.
- Choose an effective repellent with at least one of these active ingredients: Picaridin (20%), IR3535 (20%), DEET (20-30%), Oil of Lemon Eucalyptus or PMD (30-40%); it will protect against Aedes mosquitoes for at least four hours.
- Avoid blends of essential oils; some may work for a short time, but others are ineffective against Aedes mosquitoes.
- Spray your feet and ankles; the Aedes mosquito is particularly attracted to feet.
- Apply sunscreen (if needed) before repellent so the SPF doesn’t mask the repellent; reapply both after swimming and sweating.
- Don’t use repellents on infants under six months (cover strollers and baby carriers with fine netting instead), avoid using Oil of Lemon Eucalyptus or PMD on kids under three and never use more than 30 percent DEET on anyone.
- Wash your hands after applying repellent; wash clothing and repellent-coated skin at the end of the day.
Source: Environmental Working Group
Why Mosquitos Love You So Much
Mosquitoes have their favorite foods, just like people do. Males sip nectar from plants, and sometimes females do, too—but when a female is getting ready to lay eggs, she needs the extra protein that comes from dining on blood.
That blood can come from humans, but many of the world’s 3,500 mosquito species drink animals’ blood instead of or in addition to humans’ blood. For example, some Culex species have a taste for birds, but will feed on humans if they are trapped indoors.
Some people attract mosquitoes more than others, so a mosquito that happens upon your backyard barbecue might prefer you to your friends. Here are some factors that may make you a tastier treat:
Your blood type
A 2004 study published in the Journal of Medical Entomology put mosquitoes into a box in which two people with different blood types had inserted their arms. Faced with a choice between type O and type A people, Aedes albopictus mosquitoes landed twice as often on people with type O blood. The mosquitoes seemed to be able to smell the sugar chains that define our blood type. They seemed to like type B blood a little more than type A, but not as much as type O.
Before a mosquito gets close enough to decide whom to bite, it has to find where the people (or animals) are in the first place. So when a mosquito is flying around your backyard, it’s sniffing around for carbon dioxide—the stuff you exhale. The bigger you are, the more carbon dioxide you produce. If you’re exercising and breathing hard, you’ll produce even more. And a 2000 study in The Lancet found that pregnant women attracted twice as many mosquitoes as their nonpregnant counterparts—they exhaled more carbon dioxide and had higher body temperatures, so mosquitoes could detect them more easily.
The bacteria that live on your skin
We all have a coating of friendly bacteria on our bodies. In a 2011 study published in PLOS ONE, scientists compared the bacteria on people mosquitoes seemed to love, versus those less attractive to the insects. The researchers speculate that some of the less-attractive people have bacteria that break down chemical signals before mosquitoes can smell them.
Whether you’ve been drinking or not
Mosquitoes seem to prefer the smell of people who have been drinking alcohol. In a 2010 study published in PLOS ONE, Anopheles gambiae mosquitoes, which carry malaria in Africa, were most attracted to people who had consumed a beer. The same people before drinking beer, or a different group who only drank water, were less interesting to the mosquitoes. —B.S.