By Michelle Myers, PharmD Candidate, University of Pittsburgh School of Pharmacy Class of 2016
One afternoon in mid-January, sitting across from my grandmother at one of our favorite lunch spots in Pittsburgh, I heard the first rumblings of the Zika virus. There was that comfortable silence that comes only when you’re both happily chewing your first bite of food and then “So, they’ve taught you all about that Zika virus haven’t they?” By “they” she meant my pharmacy school. You see, my grandmother, who I’m proud to say is turning eighty in April, has a love for the news and day-time TV that is matched only by her excitement to share both with me, her oldest granddaughter and soon-to-be pharmacist. So naturally, I was not surprised when the latest health news story pulled up a seat at our table. What did surprise me, though, was my response: “No, I haven’t heard. What’s the Zika virus?” She smiled at the opportunity to teach me a thing or two. I thought back to my infectious disease class and recounted every virus, every bug, every infection I’d ever learned: no Zika. So I wondered about this Zika virus – what it was, where it came from – and how its story came to join us for lunch in Pittsburgh, Pennsylvania.
There’s a good reason why I never learned about the Zika virus. Prior to May 2015, Zika was limited to Africa, Southeast Asia, and the Pacific Islands. In recent years, there have been outbreaks in Pacific Yap (2007) and French Polynesia (2013), but never in the Americas. However, while the virus was evading US media spotlight, it was also traveling.
The Zika virus is an infection carried by the Aedes mosquito. There are several different species of Aedes, but the two responsible for the Zika epidemic in Brazil are Aedes aegypti (“yellow fever mosquito”) and Aedes albopictus (“Asian tiger mosquito”). These are the same mosquitoes that carry yellow fever, dengue and chikungunya viruses. The yellow fever mosquito lives near people in urban areas, both inside and outside. The Asian tiger mosquito lives in forested areas and gardens, and has been dubbed the most invasive mosquito species in the world. Both species of Aedes prefer tropical and subtropical regions, and lay their eggs in shallow water-holding containers such as flowerpots, plants, tree holes, toilets and used tires. So nearly 5,000 suspected cases, 28 South American countries, and three US territories later (Puerto Rico, US Virgin Islands and American Samoa), what brought these mosquitoes to Brazil? Trade – primarily tire trade.
Both species of Aedes mosquito can be found in the continental United States, although their distribution is largely limited to the southeast and small sections of the southwest. As of March 9, 2016 however, there has not been a single “local” case of Zika virus contracted from a mosquito in the US. In other words, to our knowledge, the mosquitoes here in the States are not infected with the Zika virus. With the exception of US territories, where there have been 173 Zika cases from locally infected mosquitoes, US residents have only become infected during travel to tropical regions (Mexico, the Caribbean, Central and South America, and the Pacific Islands). To date, there have been 193 travel-associated cases in the US.
There are three main ways to become infected with the Zika virus. The first is to be bitten by an infected Aedes mosquito. Peak biting time is at dawn and dusk. The second way to become infected is through sexual contact with an infected male partner, of which the number of cases continues to increase. Symptoms develop a few days after being bitten and are surprisingly mild, including slight fever and rash, conjunctivitis (pink eye), muscle or joint pain, and general fatigue or feeling unwell. Symptoms usually last one week or less, which is about as long as the virus remains in your blood. In rare cases, infection with Zika virus has been linked to Guillain Barré syndrome, an autoimmune condition by which the immune system attacks the nerves.
“Oh it’s just terrible! Mothers are passing it on to their newborn babies.” Unfortunately, my grandmother was right. A Zika virus infection in a normal, healthy adult is rather unimpressive; in fact, in 80% of cases people don’t even know they have it. The problem is that serious complications arise when a mother becomes infected during pregnancy and transmits the virus via shared blood to her unborn child, our third and final route of Zika infection. On November 28, 2015, the Ministry of Health of Brazil announced that as cases of microcephaly (a birth defect of the brain) in newborn babies had been increasing in northeast Brazil, so were cases of Zika virus infection. It has not been one hundred percent confirmed that Zika virus causes this rare birth defect, but researchers are currently investigating.
During pregnancy, a baby’s head grows to make room for the growing brain. In cases of microcephaly, the brain stops growing, therefore the baby’s head stops growing, resulting in a smaller than normal head circumference at birth. Complications of microcephaly include seizures, developmental delay, intellectual disability, movement or balance problems, feeding problems, hearing loss and vision problems. According to recent research, an unborn child is at greatest risk for microcephaly when the mother is infected with Zika virus during the first trimester of pregnancy. Once the virus is cleared from the mother’s bloodstream, which as we discussed takes about one week, the virus should not affect future pregnancies.
There is not currently a vaccine for Zika virus. Therefore, the best and only way to prevent Zika virus infection is to avoid travel to tropical and subtropical regions while you (or your partner) are pregnant or trying to become pregnant. For others traveling to these regions, you should take extra precautions to prevent mosquito bites: (1) use insect repellent that contains DEET, picaridin, oil of lemon eucalyptus (OLE), para-methane-diol (PMD) or IR3535 for longer-lasting protection, and follow product directions for applying and regularly reapplying, (2) wear long-sleeved pants, shirts and hats, especially during the hours of dawn and dusk, (3) stay or sleep in screened-in, air conditioned rooms, using a bed net if exposed to outdoors, and (4) apply permethrin-containing insect repellent to clothing, shoes, bed nets and tents (but not directly to skin) to continue to repel mosquitoes even after several washings.
If you think you have been infected by the Zika virus, seek medical attention from your doctor and be sure to let him or her know of any recent travel. There is a blood test coordinated by the PA Department of Health that can be used to confirm whether you have been infected with Zika virus. However, results may take time, as samples must be routed to the Centers for Disease Control and Prevention (CDC). As of March 7, 2016, there have been six blood-test confirmed travel cases of Zika virus in the state of PA and there are currently 211 blood tests pending.
I walked my grandmother up the stairs of the two-story home where she has lived for fifty years. “See you next Tuesday!” I called as she kicked up her feet at the kitchen table and flipped to the 5 o’clock news on her little white TV next to the sink. As I closed the front door and smiled to myself, I wondered about the next big news story my grandmother would hear, and how next time I would be better prepared.