The World Health Organization (WHO) declared a "public health emergency of international concern" on Monday as the Zika virus continues to spread throughout South and Central America and the Caribbean and as more travelers from the United States and Europe become infected while abroad.

The virus, which may be linked with a birth defect called microcephaly, is transmitted through the bite of an infected Aedes species mosquito. The same mosquito spreads dengue and chikungunya. Symptoms include fever, rash, joint pain and conjunctivitis (red eyes). Currently, no vaccine is available, according to the Centers for Disease Control and Prevention (CDC).

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Here are five facts you should know now.

1. The CDC continues to broaden its travel alerts. As the virus spreads the list of countries the CDC advises pregnant women to postpone travel to grows. Here is the current list of countries under a CDC travel alert.

2. Florida has declared a state of emergency in five counties. So far 12 people in Florida have been diagnosed with the Zika virus according to ABC News. All of them caught it outside of the United States.

3. The virus can be transmitted through sex. A person in Texas apparently caught ZIka through sex with a partner who likely acquired it during a trip to Venezuela. The CDC reminds people that condoms help prevent the spread of sexually transmitted infections. Health officials are currently investigating how long the virus remains viable in semen, CDC director Tom Frieden, MD, told CNN on Tuesday.

Other than the Texas case, no locally transmitted Zika cases have been reported in the continental United States, but the CDC notes that “imported cases could result in local spread of the virus in some areas of the United States.”

4. It can be transmitted through blood transfusions. Two cases of Zika spread through blood transfusions have been reported in Brazil, according to Reuters.

The Red Cross has asked prospective blood donors who recently traveled to Zika-ridden areas to wait at least 28 days before giving blood.

Related: Zika Disease: Another Way Global Warming Could Make You Sick

5. You may be able to get a refund if you have a flight to an area affected by Zika. Several major airlines are allowing customers with tickets to these areas to postpone or cancel their trips with no fee. American Airlines asks pregnant women to provide a doctor’s note confirming the pregnancy.

Prevention

If you do visit any of the affected countries, protect yourself against mosquitoes. The CDC recommends:

  • Using insect repellent with DEET
  • Wearing long sleeves and pants
  • Staying in places that have air conditioning or windows and door screens

Related: Natural Mosquito Repellants: Which Ones Work?

This story was updated on February 4, 2016.

Muriel Vega is a writer with a passion for budget travel and staying safe while abroad. A Georgia State University graduate, she has over 6 years of editorial experience and has written for The Guardian, The Atlantic, The Billfold, among other outlets. In her free time, you can find her baking pies, playing with her two dogs and cat, or planning her next vacation. She spends way too much time on Twitter, one of her favorite social media channels. Her favorite safety tip: Make sure you have all the necessary shots before you go abroad.