Mosquitoes and Zika Virus: What You Need to Know

Mosquitoes and Zika Virus

Sign or symptom	Likely cause	Risk level	What to do next
Fresh activity related to Mosquitoes and Zika Virus	mosquitoes are active nearby or recently passed through the area.	High if signs repeat or appear in multiple rooms.	Inspect the surrounding cracks, seams, food sources, and travel paths.
Old or isolated evidence	A past problem, accidental introduction, or inactive nesting site.	Moderate until you confirm whether activity is current.	Clean and mark the area, then recheck in 24 to 48 hours.
Multiple signs together	A developing infestation rather than a one-off sighting.	High because populations can spread before they are obvious.	Start control steps immediately and consider professional inspection.

Zika virus captured global attention during the 2015-2016 epidemic when its devastating link to birth defects became clear. Transmitted primarily by Aedes mosquitoes, Zika remains a concern for pregnant women and those planning pregnancy in affected regions. Understanding transmission, risks, and prevention is essential for making informed travel and family planning decisions.

How Zika Spreads

Zika virus is primarily transmitted through the bites of infected Aedes aegypti and Aedes albopictus mosquitoes. These species are daytime biters found in tropical and subtropical regions worldwide.

Unlike most mosquito-borne diseases, Zika can also be transmitted through:

• Sexual contact with an infected person
• From mother to fetus during pregnancy
• Blood transfusion (rare)

This dual transmission pathway through mosquitoes and sexual contact makes Zika unique among mosquito-borne diseases.

Symptoms

Approximately 80 percent of people infected with Zika experience no symptoms at all. When symptoms do occur, they are typically mild and last two to seven days:

• Low-grade fever
• Skin rash (often maculopapular)
• Joint pain, especially in the small joints of the hands and feet
• Conjunctivitis (red eyes)
• Muscle pain
• Headache

Severe illness requiring hospitalization is rare, and death from Zika is extremely uncommon. The primary danger of Zika lies not in the acute infection itself but in its effects on pregnancy and its association with neurological complications.

Pregnancy Risks

Zika virus can cross the placenta and infect the developing fetus at any stage of pregnancy. Congenital Zika syndrome can cause:

• Microcephaly: Abnormally small head size due to incomplete brain development
• Brain abnormalities: Including calcifications, ventriculomegaly, and cortical malformations
• Eye defects: Scarring and structural abnormalities of the retina
• Joint contractures: Limited movement in affected limbs
• Hearing loss

Not all pregnancies affected by Zika result in birth defects, but the risk is significant enough that health authorities recommend pregnant women avoid travel to areas with active Zika transmission.

Where Zika Occurs

Zika is present in tropical and subtropical areas of:

• Central and South America
• The Caribbean
• Southeast Asia
• The Pacific Islands
• Parts of Africa

Local transmission in the continental United States has been documented in Florida and Texas, though sustained transmission has not been established.

Prevention

Prevention is especially important for pregnant women and those planning pregnancy:

• Check CDC travel notices before traveling to tropical destinations
• Use EPA-registered repellent containing DEET, picaridin, or IR3535 during daytime hours
• Wear long-sleeved shirts and long pants
• Stay in places with air conditioning or window screens
• Use mosquito nets if sleeping in unscreened rooms
• Practice safe sex to prevent sexual transmission after potential exposure
• Eliminate standing water around your home to reduce Aedes breeding sites

Testing and Treatment

Blood and urine tests can detect Zika virus infection. There is no specific antiviral treatment; care is supportive and focuses on rest, fluids, and pain management with acetaminophen (not aspirin or ibuprofen until dengue is ruled out, as both Aedes-transmitted diseases have overlapping symptoms).

There is currently no approved Zika vaccine, though several candidates are in clinical trials.

For a broader view of diseases mosquitoes carry, see our mosquito-borne diseases guide and the complete guide to mosquitoes.

Travel Planning and Zika

For travelers, especially those who are pregnant or planning pregnancy, Zika requires careful trip planning:

Before Travel

• Check the CDC Zika travel information page for current outbreak areas and risk levels
• Consult a travel medicine specialist, especially if pregnant or planning pregnancy
• Stock up on EPA-registered repellent and permethrin-treated clothing
• Consider postponing travel to active Zika areas if pregnant

During Travel

• Apply repellent consistently throughout the day, as Aedes mosquitoes are daytime biters
• Stay in accommodations with air conditioning or intact screens
• Sleep under a mosquito net if screens are not available
• Wear long sleeves and pants, especially during peak Aedes activity (early morning and late afternoon)

After Travel

• Continue using repellent for three weeks after returning from a Zika-affected area, as you could be viremic and transmit the virus to local mosquitoes
• Couples planning pregnancy should wait at least two months (for women) or three months (for men) after potential Zika exposure before attempting conception
• Use condoms or abstain to prevent sexual transmission during the waiting period
• Report any symptoms to your healthcare provider and mention your travel history

Zika and the Future

While the explosive 2015-2016 epidemic has subsided, Zika has not disappeared. The virus continues to circulate at lower levels in tropical regions. Population immunity built during the epidemic may wane over time, potentially setting the stage for future outbreaks.

Research continues on multiple fronts:

• Several Zika vaccine candidates are in clinical trials
• Novel mosquito control technologies, including genetically modified Aedes aegypti and Wolbachia-infected mosquitoes, are being deployed in pilot programs
• Improved diagnostic tests are being developed for faster, more accurate detection

The most reliable protection remains personal prevention and community-level mosquito control. For a comprehensive approach, visit the complete guide to mosquitoes.

Expert Observations

The 2016 Zika virus outbreak fundamentally changed how I approach Aedes mosquito management. During that period, I consulted with several families with pregnant members in coastal South Carolina, helping them implement aggressive source reduction and physical barrier strategies. The heightened awareness around Zika led to lasting improvements in container management practices in those communities. Even though Zika transmission has declined significantly since 2016, the Aedes control measures we put in place remain valuable for preventing dengue and chikungunya as well. — Sarah Mitchell, BCE

Citations and Further Reading

• CDC – Zika Virus – CDC information on Zika virus transmission, symptoms, pregnancy risks, and prevention.
• WHO – Zika Virus Disease – WHO global overview of Zika virus epidemiology and public health recommendations.
• EPA – Mosquito Control and Zika Prevention – EPA guidance on integrated mosquito management strategies for Zika virus prevention.
• American Mosquito Control Association – Zika Resources – AMCA technical guidance on Aedes surveillance and community response to Zika.
• University of Florida – Zika and Aedes Mosquitoes – Research on Zika virus vector biology and transmission dynamics in the southeastern United States.

Main Causes

Zika virus is transmitted primarily by Aedes aegypti and, to a lesser degree, Aedes albopictus mosquitoes--both invasive day-biting species capable of breeding in containers as small as a bottle cap. The virus circulates in a human-mosquito-human transmission cycle: a mosquito acquires the virus by feeding on a viremic person and becomes capable of transmitting it to subsequent hosts after an extrinsic incubation period of roughly one week. Sexual transmission from an infected male partner--documented in multiple countries--can sustain local spread in the absence of active mosquito transmission. Transfusion-associated transmission has also been confirmed. The geographic range of Zika risk corresponds closely to the range of Ae. aegypti, which prefers warm, humid urban environments with abundant artificial container habitats. In the continental United States, locally acquired mosquito-borne cases have been documented in Florida and Texas during outbreak years when Ae. aegypti populations are high and imported cases seed local transmission.

Risk and Severity

For most infected adults, Zika produces mild illness or no symptoms: roughly 80 percent of infections are asymptomatic, and symptomatic cases typically resolve within a week. The severe and defining risk is congenital Zika syndrome in fetuses when infection occurs during pregnancy. Microcephaly, brain malformations, eye defects, hearing loss, impaired growth, and joint abnormalities have all been documented. The CDC and WHO classify Zika infection during pregnancy as a serious public health concern. Risk is not uniform: first-trimester infection carries the highest probability of fetal brain malformation, though adverse outcomes have been reported after infection in all trimesters. Guillain-Barre syndrome has been associated with Zika infection in adults, though the absolute risk remains low. Travelers to active transmission areas face real exposure risk, as does anyone in a US county with established Ae. aegypti populations during a local outbreak. Current risk levels by country are tracked and updated by CDC Traveler's Health.

How to Identify

Identify the active species and its breeding site before treating. Container-breeding species like Aedes aegypti and Asian tiger mosquitoes are day-biting, prefer artificial containers around homes, and produce eggs that survive months of drying. Culex mosquitoes are dusk-to-dawn biters that breed in standing water with organic content — clogged gutters, ditches, and stormwater catch basins. Walk the entire property and identify every container, depression, and surface holding water for more than a week. A flashlight inspection of standing water at night reveals wriggling larvae and tumbling pupae near the surface, confirming an active breeding site. Indoor activity usually traces to a single nearby breeding source, not to an interior breeding population.

Solutions and Actions

Mosquito control hinges on removing breeding water first. Walk the entire property weekly during mosquito season and dump every container, gutter, birdbath, plant saucer, and depression holding standing water. Treat ornamental water features with Bti larvicide (mosquito dunks) which is safe for fish, pets, and people. For yard adult activity, apply a residual insecticide barrier treatment to shaded resting areas — under decks, dense shrubs, fence lines, and woodlot edges. For individual protection during outdoor activity, use EPA-registered repellents containing DEET, picaridin, or IR3535 on exposed skin and treat clothing with permethrin. Inspect and repair window and door screens. Properties next to wetlands or drainage features may benefit from a professional barrier treatment program during peak season.

Frequently Asked Questions

Is Zika virus still a concern?

Global Zika transmission has declined significantly since the 2015-2016 pandemic, but the virus has not been eliminated. Sporadic outbreaks continue in tropical regions, and the Aedes mosquitoes that transmit Zika remain widely distributed in the southern United States. Pregnant women and women planning pregnancy should stay informed about current Zika activity in their area.

How does Zika affect pregnancy?

Zika infection during pregnancy can cause microcephaly and other severe brain defects in the developing fetus. The virus can be transmitted from mother to fetus during pregnancy or around the time of birth. Pregnant women should take extra precautions to avoid mosquito bites and avoid travel to areas with active Zika transmission.

Which mosquitoes spread Zika virus?

Aedes aegypti is the primary vector of Zika virus. Aedes albopictus can also transmit the virus but is considered a less efficient vector. Both species are daytime biters found in the southern United States, which means repellent use during the day is essential in areas where these mosquitoes are present.

Can Zika be transmitted sexually?

Yes. Zika virus can be sexually transmitted from an infected person to their partner, even if the infected person does not have symptoms. The CDC recommends that men who have traveled to Zika-affected areas use condoms or abstain from sex for at least three months after travel to prevent sexual transmission.