Zika virus, a previously obscure disease that had only caused a handful of cases in Africa and some island nations, is now a major global health concern. It's been linked with brain damage in babies, and the World Health Organisation just declared South America's Zika epidemic a public health emergency. You may not live in South America, but in today's world of global travel and fast-moving infections, let's talk about whether you need to worry.
What is Zika and Why Are People Worried About It?
Zika might cause brain damage in newborns if their mothers contract the virus while pregnant. There is no vaccine for Zika, no cure and no way that we know of (yet) to prevent Zika from harming a baby. The good news is that Zika and its complications are rare.
Zika virus causes fever, rash, joint pain and bloodshot eyes in about 20 per cent of the people who contract it, and no symptoms in the other 80 per cent. It's a member of the Flavivirus genus, making it a relative of yellow fever, chikungunya and dengue viruses. Like them, it's transmitted by mosquito bites.
Until recently, nobody was very concerned about Zika. It was rare, and it wasn't associated with serious complications. But there's recently been a huge explosion in cases of suspected microcephaly in newborns in Brazil. The US CDC has advised women who are or might be pregnant not to travel to the countries where Zika is spreading.
The link between Zika and microcephaly is not proven, but it's plausible. Zika arrived in Brazil recently, possibly during the 2014 World Cup, and the surge in microcephaly cases followed. More worldwide spread is possible -- the 2016 Summer Olympics will be held in Rio de Janeiro in Brazil. (Athletes are stocking up on bug spray.)
The Brazilian government is now investigating over 4000 cases where babies have heads smaller than 33cm around, compared to just 150 cases in a typical year. That large number may be inflated; more than half of the babies investigated so far just had small-but-normal heads, or had microcephaly for some other reason. But whatever the exact numbers, there is definitely a surge, and fingers are pointing at Zika.
I'm Not a Pregnant Woman. Should I Worry?
Maybe a little. You don't have to be pregnant to experience the virus's other possible complication, Guillain-Barre syndrome. And there's a possibility that someone who contracts the disease via mosquito could pass it on as a sexually transmitted disease.
Guillain-Barre syndrome (GBS) is a rare condition where a person's immune system attacks their nerve cells. Paralysis can result. It can be triggered by an infection, including Campylobacter (a form of food poisoning), or even the flu.
The link between GBS and Zika is unsure. Brazil's Ministry of Health noticed a surge in GBS cases around the same time as the surge in Zika cases, so they and the US's Centres for Disease Control and Prevention (CDC) are investigating.
Sexual transmission of Zika is also still mostly theoretical. One man in 2007 was found to have blood and Zika in his semen; another man, a researcher, may have given his wife the Zika virus upon returning from a research trip. That's the sum total of our knowledge on the topic. Commenting on these cases, infectious disease specialist Scott Weaver told the New York Times, "If I was a man and I got Zika symptoms...If my wife was of childbearing age, I'd want to use protection, for a few weeks at least."
If sexual transmission exists, it's probably rare, but still worth considering. If you travel to a Zika outbreak area, you might want to pick up some condoms on your way home.
There's one other consideration. If you're not pregnant or trying, but would consider keeping a surprise baby, you may want to follow the same precautions as for women who are pregnant. In other words, up your birth control game before and during your trip, and be really fastidious about the bug spray just in case.
Will Bug Spray Keep Me Safe?
Yes! Nothing is foolproof, but insect repellents containing DEET are very effective at keeping mosquitoes away. Some brands with picaridin or oil of lemon eucalyptus work well too.
DEET is safe, in case you were wondering, and the CDC's travel advice explicitly includes a statement that all three repellents are safe in pregnancy. Make sure to reapply often; here are the results from a test of how popular US brands fared after hours on the skin.
Where Am I Most at Risk? Is Zika Coming to Australia?
The CDC's list of Zika-affected areas is here. It currently includes 25 countries and territories in the Americas, plus a few islands elsewhere in the world. Mexico and a good chunk of South America are included. Australia is not.
Microcephaly cases are highlighted below. (This is just a screenshot of a really awesome interactive map -- check it out for more details on each country.)
Zika was first found in Africa, but there have only ever been a handful of cases in miscellaneous African and other countries until the recent outbreak.
Zika virus and its relatives are transmitted by mosquitoes, mainly the species called Aedes aegypti. It has little white spots on it, and bites during the day. Fears about Zika (and dengue, and chikungunya) spreading are based on the range of these mosquitoes, which extends into northern Australia -- see the map below. Note that the viruses aren't widespread in all of these areas yet, but if they arrived, mosquitoes would be available to transmit the disease.
So it's possible that Zika and these other viruses can come to Australia. The mosquitoes are also spreading, as temperate regions get warmer and stay warm longer, thanks to climate change. But, like the US, the chance of a major Zika outbreak in Australia is fairly low because most people in the Australia hang out indoors in the air conditioning, install window screens, use bug repellent and keep their yards free of standing water. (If you don't keep your yard free of standing water, please go out and dump that birdbath. You're breeding mosquitoes for the whole neighbourhood.)
If I Go to a Zika Affected Area, What's the Chance of Having a Baby With Microcephaly?
The risk is small. Nationwide, Brazil's 4000 cases of suspected microcephaly are around one-tenth of one per cent of all the country's births in 2015.
That number is not too far off from the rate of microcephaly in the US caused by a virus called cytomegalovirus (CMV). And back before we had a measles-mumps-rubella vaccine, the rubella virus often caused microcephaly, too. So this isn't a huge jump from the risks you were already ignoring.
So the risk of having a baby affected by Zika is very small, even if you do travel to Brazil while you're pregnant. It's definitely worth being careful about mosquitoes, and you may want to heed the travel advisories and cancel your trip. But the risk is perhaps smaller than you feared.
How Would I Find Out if my Baby Has Zika?
Definitely tell your doctor if you've been to a country with Zika while you're pregnant, especially if you had a rash, fever or something that seems like pink eye. The CDC put out recommendations for appropriate testing and treatment; you might want to bring a copy to your doctor. (Vox has translated them into flowchart form here.) The suggestions include:
- Sending a blood sample to the state health department for testing. This works best within a week of infection. If you've had Zika in the past, the health department can test for antibodies, but that result is less precise.
- Considering amniocentesis, which means taking a sample of the amniotic fluid surrounding a baby. This test is risky by itself, with a 0.1% chance of miscarriage if it's performed before 24 weeks. The fluid can then be tested for Zika.
- Performing ultrasounds every 3-4 weeks to look at the baby's brain development, if a blood test or amniocentesis turned up positive results.
There's a major caveat here: We don't know how test results relate to a baby's chances of being born with microcephaly or other complications. Microcephaly also often can't be detected by ultrasound until 24 weeks or later -- after most states' cutoffs for legal abortion.
If it turns out that you may have had Zika, you're in a very tough situation with a lot of unknowns. We don't know how likely microcephaly is for somebody with a positive blood or amnio test, and we don't truly know how babies with microcephaly from Zika will be affected throughout their lives.
How Will Zika Affect Children as They Grow Up?
"Microcephaly is a box of surprises," writes journalist Ana Caceras for the BBC. Doctors told her mother she would never walk or talk, but they were wrong. On the other end of the spectrum, many babies with microcephaly do live up to those drastic, dramatic pronouncements. Brazil's cases seem to include many of the more severe cases.
Microcephaly from Zika is a new thing, so guesses about the babies' futures are based on what we know of microcephaly from other causes, including infections with other viruses. Cytomegalovirus, for example, also seems to destroy stem cells in the developing brain, leaving it with less tissue to work with. Zika might do the same.
The Brazilian babies who are affected are getting treatments that may include physical therapy to help strengthen their muscles, which can also be affected by microcephaly, and medication for seizures. There's no way to reverse it, so health care providers are trying to manage symptoms and work to understand the condition as best they can.
What Are Governments and Scientists Planning to Do About This?
Without a vaccine or a reliable treatment, there's not a whole lot they can do in the short term. Countries like the US are advising pregnant women to reconsider their travel plans, and the governments of countries with Zika are telling women they might not want to get pregnant anytime soon.
Brazil and El Salvador have recommended that women who live there delay pregnancy -- in El Salvador's case, until 2018. But that's not easy advice for residents to follow. In El Salvador, for example, condoms are expensive, the pill is hard to get and the most popular form of birth control is sterilisation surgery.
The World Health Organisation, in declaring the Zika outbreak a Public Health Emergency of International Concern, named some action items, including these:
- The WHO says developing better tests is top priority for researchers, more important even than developing vaccines and treatments. Without a good test, it's hard to know who needs treatment or how big the problem even is.
- Mosquito control is also super important, and people -- especially pregnant women -- need to have the tools they need to avoid mosquitoes to reduce their risk of getting Zika.
- Health services in the affected countries should get ready to provide lots of help to people affected by the virus -- for example, neurologists and physical therapists to support babies as they develop.
- The WHO did not recommend any restrictions on travel or trade, but several countries (including the US) have issued travel advisories for pregnant women.
The most effective ways to control Zika in the short term are likely to be the ones focused on keeping mosquitoes away from people, even eliminating mosquitoes or eliminating the Aedes aegypti species, which isn't native to Australia anyway. The first step is to get rid of obvious sources of standing water, since mosquitoes can breed in pothole puddles and rain-filled buckets.
Beyond that, there are many possible mosquito control strategies including mass spraying of insecticides (which sounds scary, but then so does microcephaly); releasing genetically-modified male mosquitoes that mate with females but cannot produce fertile offspring, reducing the number of mosquitoes in the next generation; and releasing mosquitoes infected with Wolbachia, a mosquito-only infection that likewise makes them sterile. Controlling mosquitoes wouldn't just reduce the spread of Zika. The same mosquitoes also carry other viruses like dengue, so it's a good public health measure all around.
Vaccines for Zika are in development, and may be ready for their first human tests by the end of the year. With luck, we'll have better answers to all of Zika's unknowns in the coming years. The babies with microcephaly will begin to grow up, and we'll learn how severely affected they really are. Over time, the therapists working with those babies will figure out the best ways to help them.
For now, it's hard to say exactly how big a deal Zika is, but we're learning. Because it's so rare, you don't need to freak out. But since the complications can be serious, it's wise to take extra precautions.