Just last week, the CDC reported the first cases of Zika virus that were transmitted by mosquitoes in the United States. As of today, there have been a total of 15 cases identified in patients in Miami, FL. While Zika’s migration to the United States comes as no surprise, as the CDC has been monitoring for cases for months now, it is significant. Prior to these cases, there had been over 1,600 cases of Zika diagnosed in the United States, but these patients all acquired the virus while traveling in other countries.
I often find myself trying to stomp out panic, because people tend to get worked up over some pretty ridiculous things. But while panic is never useful, this virus is actually a reason to be concerned. There’s a lot we’re still not sure about, but let’s take a look at what we do know about Zika virus, why we should be concerned about it, and what we can do to prevent it.
The Zika virus was initially discovered in Ugandan monkeys in the 1940’s, and was first identified in humans in 1952. Since that time, the virus hasn’t tended to cause a lot of problems. The symptoms of infection are similar to a lot of other tropical, mosquito-borne infections—usually mild fever, headache, body aches, rash, or joint pain (if anything). Many infections go totally unnoticed, and the virus is very unlikely to require hospitalization. None of that sounds particularly scary.
The reason you’ve even heard of Zika virus is because there has been an increase in severe complications associated with this infection. The virus has been implicated in triggering Guillain-Barré syndrome, an auto-immune disease in which the immune system attacks the nervous system. This causes severe muscle weakness and can be fatal if it progresses to involves the muscles involved with breathing. And then in late 2015, there were reports from Brazil of a significant increase in the number of infants born with microcephaly, a condition involving under-development of the infant’s brain. Some of these cases are fatal, and those that aren’t will most likely have severe and permanent neurological problems. Many of these cases were later linked to transmission of Zika virus across the placenta from an infected mother. And that makes Zika a really big deal.
Zika virus is transmitted by a certain type of mosquitoes that inhabit much of the United States, as well as more tropical climates. Obviously, not every mosquito carries the virus, so the vast majority of mosquito bites will result in nothing more than an itchy bump. But when one of these mosquitoes bites someone infected with Zika virus, it can then transmit the virus to its next victim. Mosquitoes don’t tend to travel far, so the geographical spread of Zika virus grows because of human travel—someone travels to a different location (most likely unaware that they are infected), and gets bit by another mosquito who then transmits the virus to others.
Insect-borne infections aren’t new—there’s a wide array of diseases that are caused by parasites or viruses transmitted by mosquitoes, ticks, or other insects. What’s different about Zika (aside from the complications it can cause), is that is can also be transmitted sexually. This was first discovered in 2008 when a scientist who had been working overseas when he acquired the infection returned home and passed the virus to his wife by sexual contact. This is why people who have risk factors for Zika exposure, like travel to an area with reported infections, should avoid sex or be sure to use condoms–especially if their sexual partner happens to be pregnant.
As far as its own survival goes, Zika does a pretty good job. The fact that many people don’t develop symptoms plays a big role in promoting transmission, because people may be infected without realizing that they could be spreading the virus to others. (Contrast this with Ebola, which is spread by people who have already developed symptoms or died from the virus.) This trait—combined with the severe problems it can cause and the likelihood that it will continue to spread—makes it vital for us to do everything we can to limit the spread of this virus.
There are vaccines currently in the development and testing stages, but we’re a long way out from showing that these are safe and effective enough to use. This wouldn’t be the first time we’ve used a vaccine to prevent birth defects from an otherwise mild virus—the rubella vaccine is used for the same reason.
But until we have a better solution, we’re limited to good, old-fashioned bug bite prevention. One of the most important things you can do to limit your exposure to mosquitoes is to minimize any standing water around your home. These environments are where mosquitoes breed, so getting rid of them helps to keep the population under control. Chemical treatments are an option for small areas where people congregate (like the Rio Olympics that start this week), but are far too expensive to treat an entire state or country.
Other options to minimize your exposure are to stay indoors with the windows and doors closed, or to use screens or netting for camping or other prolonged outdoor activities. Long pants and long-sleeved shirts are an effective way to prevent bites, and they don’t present any risk of side effects (except maybe sweating). Avoiding times of day when mosquitoes are most active can help, although mosquitoes seem to favor the same cooler evening hours that I do.
And then there’s insect repellent. There are a lot of options out there, so I’ll try to break them down for you:
First developed in 1946, DEET is the most frequently-used insect repellent out there. There were some safety concerns in the 1980’s about children who developed neurological problems after DEET exposure (both topically and ingested), but these were never specifically linked to DEET—they most likely just happened to occur around the same time. Further studies were performed to evaluate these reports, and after monitoring for 6 years, there were 300 serious complications reported, of which about 120 were related to seizures or other neurological symptoms. Again, it’s very likely that many of these events weren’t caused by DEET exposure. Even if you assume that they were related, given that about 100 million people in the US use DEET-containing products each year, that puts the risk of a serious side effect somewhere south of one-in-a-million. As with any topical product, there’s always potential for skin irritation, but that is usually a minor issue.
Another side effect of DEET use involves not the person using it, but the gear or clothing they may be using. DEET is an oily substance that can dissolve some plastics or synthetic fabrics, so be careful about what you touch while using it.
DEET is recommended for use in children over 2 months of age, in concentrations of 10-30%. The percentage you choose doesn’t change how effective it is, but rather how long it lasts. In general, you’ll get about 2 hours of protection from a 10% product and 6 hours from a 30% product, so pick the one that best suits your intended activities.
Newer to the scene, but with similar effectiveness, is a chemical called picaridin. It doesn’t have the oily texture, smell, or potential to damage your gear—which makes it a winner in my book. It’s approved for ages 2 and up. (Studies haven’t been done on younger kids.) There haven’t been any major safety issues, but it does have a shorter track record than DEET, as it wasn’t commercially available in the US until 2005. Similar to DEET, picaridin’s duration depends on the concentration, with a 20% product lasting roughly 4 hours.
Essential oils/natural products
Those of you who follow my blog are probably aware that I can be hard on essential oils—but only when they’re promoted as miracle cures or used without any real evidence to treat serious medical problems. Using essential oils as insect repellents passes the plausibility test. (After all, plants don’t make these chemicals to make your kitchen smell good or treat your asthma—they make them, among other reasons, to avoid getting eaten by insects.)
There’s some science to back this up as well…it’s always nice when that happens. Lemon eucalyptus is the most studied and is nearly as effective as the synthetic insect repellents. Several other essential oils have some evidence behind them as well, although many of them need to be applied more frequently. It’s important to remember that just because these products are “natural” doesn’t mean they’re totally safe. Everything is made from chemicals, and anything that has potential for good effects has potential for bad effects as well.
As I said before, most mosquito bites are just mosquito bites, so if you child gets one, there’s no reason to freak out. Just rub some calamine lotion on it and move on. And even if a child gets the virus, it will most likely resolve without complication. But if you have reason to suspect this infection in yourself or your child, talk to your doctor about getting tested–there’s no specific treatment, but it is crucial that we identify cases so that we can limit the spread of this virus. If you happen to be pregnant, it’s even more crucial for you to protect yourself (by avoiding travel to places where infection is reasonably likely and using the measures I discussed above).
For any insect repellent (even the natural ones), you can minimize the risk for any problems by washing them off with soap and water as soon as your outdoor activities are over. For spray-on products, be sure to apply them outside to limit the amount that may be inhaled. Don’t spray anything in your child’s face, and don’t let them drink this stuff. Otherwise, you should be safe no matter which one you choose…as long as you use it.