9 Fast Facts You Need to Know About the Rapidly Spreading Zika Virus

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1. What exactly is the Zika virus?

The Zika virus is a mosquito-borne illness spread primarily by the yellow fever (Aedes aegypti) mosquito, which is found in the United States in Florida, along the Gulf Coast, and in Hawaii, but has been seen as far north as Washington D.C. The Asian tiger (Aedes albopictus) mosquito can also transmit the Zika virus, and travels as far north as Chicago and New York in warm temperatures.

The Zika virus was first discovered in Ugandan monkeys in 1947. It spread to the South Pacific and caused an outbreak on Yap Island in the Federated States of Micronesia in 2007. The island’s population was too small for scientists to observe whether the virus caused side effects like birth defects or neurological damage. Symptoms—fever, joint pain, red eyes, and rash—are often ignored or considered the flu.

In early 2015, Brazil experienced a spike in Zika cases, and the virus quickly spread throughout other parts of the Americas. It could have been introduced in 2014, when Brazil hosted the FIFA World Cup and an international canoeing competition. The Zika virus is now in 23 countries in the Americas.

By 2016, health officials in Brazil had noticed another disturbing trend: Rates of microcephaly, a rare birth defect in which an infant is born with an abnormally small head, were rising rapidly. More than 4,000 cases of microcephaly have been reported in Brazil since authorities began investigating the surge in October. Fewer than 150 cases were reported in 2014.

2. So, the Zika virus causes microcephaly?

Scientists aren’t positive, but it’s strongly suspected. Little has been studied about the virus until now since it typically doesn’t cause serious symptoms. Microcephaly is often not detected until after the second trimester of pregnancy, but children born with it may face developmental challenges, learning disabilities, or physical limitations.

“Infants who have a neurological problem such as microcephaly can have problems with a lot of their basic functions,” says Amanda Moen, MD, a pediatric neurologist at Gillette Children’s Specialty Healthcare. “It might be difficulty walking or talking, or it might be difficulty coordinating a swallow.” Trouble eating raises the risk of an infant aspirating milk, which can lead to potentially fatal pneumonia or respiratory infections.

The Zika virus has also been linked to Guillain-Barre syndrome, a neurological syndrome that can cause paralysis, leading experts to believe the virus may somehow affect the nervous system.

3. How would I know if I had Zika? 

Most people don’t know when they’re infected, a reason the virus is difficult to track. “Eighty percent of people who get this [virus] don’t even know they have it,” says David Colombo, MD, division chief of maternal fetal medicine at Spectrum Health Medical Group.

Symptoms are usually mild. Along with fever, joint pain, rash, or conjunctivitis (red eyes), an affected person might experience headache and muscle pain. Hospitalization is uncommon, and symptoms generally only last up to a week. However, if you notice symptoms after you’ve visited an affected region, see a doctor right away.

4. Am I still at risk for Zika if I haven’t traveled to a high-risk country?

There are no reports of local transmission in the United States, but there have been more than 30 cases of Zika infection among American citizens who visited areas affected by the virus, according to the CDC. There is a rare possibility that semen may carry the virus, but evidence is anecdotal.

“For the average American who is not traveling, this is not a problem,” Anne Schuchat, MD, of the CDC told reporters.

The states where the Zika virus has been confirmed among travelers returning from affected countries are: Hawaii, Arkansas, California, Florida, Massachusetts, Minnesota, Hawaii, New Jersey, Oregon, New York, Virginia, Texas, and the District of Columbia.

5. Can the Zika virus be prevented or cured?

There isn’t a vaccine or treatment for the Zika virus. The World Health Organization (WHO) stated it is taking steps to develop a vaccine, though it’s unlikely one will be available this year.

“I am encouraged by the fact that we do have a commercially available dengue vaccine this year, for the first time ever,” said vector biologist Laura Harrington, chair of the Department of Entomology at Cornell University, in a media video. “It is made within the backbone of the yellow fever vaccine, one of the most effective vaccines ever made. I suspect a good starting point would be trying to use that approach to design a Zika vaccine.”

6. What precautions should pregnant women take about the Zika virus?

If you’re pregnant and planning to visit (or recently visited) an area affected by Zika, and you’ve experienced symptoms of infection during your trip or two weeks after, the CDC suggests you consult your doctor and have a blood test taken.

Even if you don’t have symptoms, the CDC recommends ultrasounds for all women who have traveled to affected countries to detect if their fetuses are developing microcephaly. Unfortunately, there’s nothing that can be done to reverse the defect. However, early detection could help prepare families for the child’s needs.

“A family who is aware of a potential birth defect such as microcephaly can appropriately plan for the needs of this infant, which are going to be different from the needs of a healthy infant,” says Dr. Moen. “These mothers can then say, ‘I’m going to need a neurologist in addition to a pediatrician.’”

Government officials in Brazil, Ecuador, Colombia, and El Salvador have gone as far as to advise women to refrain from getting pregnant for up to two years. It might not be an easy solution, though: Contraceptive use in Latin American women is among the lowest in the world. Emergency contraceptive is often difficult to access, expensive, or illegal. Amnesty International estimates that more than 50 percent of pregnancies in Latin America are unplanned, and even for women who aim to abstain from sex, experts say high rates of sexual violence and strict abortion laws in Latin America may make the recommendations difficult.

7. How will the Zika virus affect the 2016 Summer Olympics?

The Rio 2016 Summer Olympics begin in Brazil August 5. A spokesman for the Rio Olympics organizing committee said there have been no discussions about moving or canceling the Games because of Zika virus, and that teams were inspecting Olympic venues daily to eliminate problems such as sitting water where mosquitoes can breed.

“Dealing with mosquito breeding grounds goes a long way, but I don’t know if there’s any way to know if that’s going to be enough,” says Christina Leonard Fahlsing, MD, an attending physician of infectious diseases at Spectrum Health Medical Group. “We won’t know until after. They’re doing a lot to decrease risk, but they certainly cannot eliminate the risk.”

The temperatures will be colder in Brazil (where it is now summer) during the games, which may kill off mosquito populations and lower risk.

8. Could Zika become more of a threat in the U.S. when the weather gets warmer?

The WHO estimates that 3 to 4 million people across the Americas will be infected within a year. Sixty percent of Americans live in areas where Zika can be transmitted during the summer. However, living conditions in the United States will likely make the country less susceptible to the spread of the virus.

“Our living conditions in general don’t favor the transmission of these viruses as easily as in other countries,” says Dr. Leonard Fahlsing. “In poorer countries, it is explosive because people live so close together and may not have windows or air conditioning. I don’t see [Zika] spreading as quickly in this country as it has in Brazil.”

9. If I’m not pregnant (or planning to be), should I worry about going to an affected country? 

Not if you strictly adhere to birth control. Women who become unexpectedly pregnant during or after a trip to an affected area will need to face blood tests, monthly ultrasounds, and likely quite a bit of anxiety.

If you’re concerned, talk to your doctor before you travel. He or she may recommend precautions such as staying in places with air conditioning, using and reapplying insect repellent as directed, wearing long-sleeved shirts and long pants, or sleeping under a bed mosquito net.