Since emerging in Brazil in early 2015, the Zika virus has now spread to more than 40 countries in the Western Hemisphere, including Puerto Rico and the U.S. Virgin Islands.

It’s a troubling and widespread global health problem—and it’s the first of its kind. If you live on the mainland U.S., health officials say you don’t need to panic.

But you should still be alert to the threat and take some extra precautions by, for example, using an effective insect repellent, as the Centers for Disease Control and Prevention predicts isolated outbreaks along the Gulf Coast this summer.  

Here's what you need to know about Zika, as well as other mosquito and tick diseases.

What You Need to Know About Zika

Concerns about Zika have sent state and federal public health officials scrambling to update mosquito-control protocols. Because anyone bitten can become an unwitting carrier of the disease, even those not trying to become pregnant need to be vigilant against mosquito bites this season.

The virus can cause microcephaly, a birth defect marked by an abnormally small head and developmental deficits. Doctors still don’t know how often the virus causes those problems, but they say Zika is the first pathogen in 50 years to trigger birth defects, and the first mosquito-borne disease ever to do so.

We’ve seen microcephaly before, notably during the rubella epidemic of 1964. But the Zika-related version is so much worse that doctors have started referring to it by a different name altogether: fetal brain disruption sequence.

“I have never seen anything like this,” says James Sejvar, M.D., a neuroepidemiologist with the CDC. Babies born with Zika-related microcephaly have significantly smaller heads than those born with other forms of the disorder, he says. And their brains are much more damaged.

The virus can also be spread through sexual intercourse and has, in rare cases, been linked to serious neurological disorders in adults, including Guillain-Barré syndrome, which can cause paralysis, sometimes permanently.

Other Mosquito Diseases

Zika isn’t the only mosquito-borne threat you need to be concerned about. Dengue—another tropical disease spread by the same Aedes mosquitoes that can carry Zika—is now common in Puerto Rico and the U.S. Virgin Islands, and sporadic outbreaks have been reported in Florida, Hawaii, and Texas. And West Nile virus, which is spread by Culex mosquitoes, is still far more common than either, infecting thousands each year and has caused 1,700 deaths in the U.S. since 1999.

Chickungunya

Most cases of this virus, which is spread by the same mosquito as Zika, still occur outside of the U.S. mainland, though infections have been reported in Puerto Rico, the U.S. Virgin Islands, and, in 2014, a few cases in Florida. There is still no vaccine to prevent the disease, and antibiotics don't work against it, making protection against mosquito bites key.
Common side effects:
Fever, joint pain, and headache, usually appearing three to seven days after a bite.
Serious side effects: Usually only in people with other health problems, such as diabetes or heart disease.
Treatments:
None of the disease itself, but acetaminophen and fluids can ease symptoms. (However, avoid aspirin or related drugs such as ibuprofen or naproxen, which may cause complications.)

Dengue

Also spread by Aedes mosquitoes, this disease is widespread throughout the tropics and subtropics around the world, including the Caribbean, and in recent years there have been outbreaks of the virus in Hawaii, Florida, and, in 2013, Texas. There is still no vaccine approved for use in the U.S., and antibiotics don't work against it, making protection against mosquito bites key.
Common side effects:
Fever, severe eye pain, muscle pain, rash, and bone and joint pain, usually appearing four to seven days after a bite.
Serious side effects: Severe damage to the body's blood vessels leading to bleeding and sometimes death.
Treatments:
None for the disease itself, but acetaminophen and fluids can ease symptoms. (However, avoid aspirin or related drugs such as ibuprofen, which may cause complications.)

West Nile

By far the most common mosquito-borne disease in the U.S., the West Nile virus infects thousands of people each year across the country and has been responsible for 1,700 deaths in the U.S. since 1999. There is still no vaccine to prevent the disease, and antibiotics don't work against it, making protection against mosquito bites key.
Common side effects: Red rash with small bumps usually two to 14 days after a bite, followed by fatigue, headache, and back pain.
Serious side effects: In rare cases, inflammation of the brain or surrounding tissue, which can be fatal.
Treatments: None for the dissease itself, but over-thecounter pain relievers such as aspirin, ibuprofen, or naproxen, plus fluids, can ease symptoms.
 

Tick Diseases

Tick diseases, such as Lyme and Rocky Mountain spotted fever are even more common, than diseases spread by mosquitoes. Some 300,000 people a year develop Lyme, according to the Centers for Disease Control and Prevention. And experts say those and other tick diseases are increasing in incidence and geographic range, possibly due to changing weather patterns.

Anaplasmosis

Most common in the Northeast and Upper Midwest, the symptoms of this disease are similar to ehrlichiosis (see below), sometimes making it difficult to distinguish between the two. It's caused by the deer, or black-legged, tick. Prompt treatment with antibiotics can greatly reduce the risk of serious complications.
Common side effects: High fever, fatigue, severe headache, and muscle aches, usually seven to 14 days after a bite.
Serious side effects: In rare cases, difficulty breathing, bleeding disorders, and death.
Treatments: The antibiotic doxycycline as soon as symptoms appear.

Babesiosis

Most common in the Northeast and Upper Midwest, this disease is caused by microscopic parasites carried by deer, or black-legged, ticks, especially in the warmer months. Prompt treatment can prevent serious complications.
Common side effects: Fever, headache, loss of appetite, chills, and body aches, usually seven to 14 days after a bite.
Serious side effects: In rare cases, difficulty breathing, bleeding disorders, and death.
Treatments: The antibiotic azithromycin plus the antiparasitic atovaquone or, in severe cases, the antibiotic clindamycin plus quinine.

Ehrlichiosis

Most common in the Southeast and South Central U.S., the disease is caused by microscopic parasites spread by the lone star tick. Symptoms of the disease are similar to anaplasmosis (see above), sometimes making it difficult to distinguish between the two. Prompt treatment with antibiotics can greatly reduce the risk of serious complications.
Common side effects: High fever and severe fatigue, headache, and muscle aches, usually seven to 14 days after a bite.
Serious side effects: In rare cases, difficulty breathing, bleeding disorders, and death.
Treatments: The antibiotic doxycycline as soon as symptoms appear.

Lyme

By far the most common tick-borne disease in the U.S., Lyme sickens some 300,000 people a year. It is caused by parasites carried by deer, or black-legged, ticks. It's common in the Northeast and Upper Midwest. Prompt treatment with antibiotics usually cures the disease, but some people experience lingering symptoms that research suggests do not improve with continued antibiotic treatment.
Common side effects:
"Bulls-eye" rash, chills, headache, fatigue, fever, and muscle pain, usually three to 30 days after a bite.
Serious side effects: In rare cases, lasting joint pain, neurologic damage, facial paralysis, or heart damage.
Treatments: Antibiotics (usually doxycycline or amoxicillin) as soon as symptoms appear.

Rocky Mountain Spotted Fever

Despite its name, this disease is actually most common in the South and South Central U.S. It's caused by parasites carried by the American dog tick, brown tick, or Rocky Mountain wood tick. Prompt treatment with antibiotics can greatly reduce the risk of serious complications.
Common side effects:
Fever, stomach pain, muscle pain, headache, vomiting, and rash, usually two to 14 days after a bite.
Serious side effects: In rare cases, heart damage, kidney failure, and if not treated within five days, sometimes death.
Treatments: The antibiotic doxycycline as soon as symptoms appear.


Editor's Note: This article also appeared in the July 2016 issue of Consumer Reports magazine.