Zika virus, a disease once only found in Africa and Southeast Asia, has spread rapidly into the Americas, bringing with it a fear of birth defects.
The illness is mainly transmitted by mosquitoes, and no one in the United States has yet been infected with Zika from a bug bite.
But the mosquitoes that carry the disease are found in California, and officials say we must limit their spread to make sure the infection doesn't take root here.
Are these the typical mosquitoes we're used to in California?
No. Californians are most familiar with Culex mosquitoes, which don't carry Zika virus.
The ones that can transmit Zika are the Asian tiger mosquito and the yellow fever mosquito — Aedes albopictus and Aedes aegypti, respectively. They're not native to California.
How did they end up here?
Experts think the infestation in L.A. County started in 2011 in El Monte. The mosquitoes are believed to have been transported from Southeast Asia in shipments of bamboo plants.
How do I know if they are near me?
Aedes mosquitoes have been found in 12 of California's 58 counties, officials say. You can check this map of the state made by the California Public Health Department to see the regions where they've been found so far.
Nationwide, Aedes mosquitoes are found in the eastern half of the United States, some southeastern states and California.
How are they different from Culex mosquitoes?
Aedes mosquitoes are about half the size of normal mosquitoes -- just about a quarter of an inch long -- and they have black and white stripes.
They're also known for being unusually aggressive. They can't be easily swatted away and readily follow people into buildings or cars.
And while most mosquitoes bite during dawn and dusk, these mosquitoes are out during the daytime.
Do all Aedes mosquitoes have Zika virus?
No. The mosquitoes are not born with the virus (or any other viruses).
The insect can only start carrying Zika if it bites someone who's been recently infected. The mosquito can then transmit the virus if it bites someone else.
Interestingly, female mosquitoes are the only ones that bite, said Dr. Jim Fredericks, chief entomologist for the National Pest Management Assn. "Male mosquitoes typically feed on nectar," he said.
Aedes mosquitoes can also transmit dengue and chikungunya, diseases which kill thousands of people each year in other parts of the world.
I've never seen these mosquitoes near my home. Do I need to do anything?
Public health officials recommend that you wear insect repellent and clothing that covers most of your body, especially if you're in an area where there's a reported infestation. The same applies if you're traveling to a place where there's an outbreak.
The U.S. Centers for Disease Control and Prevention is regularly updating this list of countries with Zika outbreaks.
It's also a good idea to use screens on your windows, which will also help keep out Culex mosquitoes, which transmit West Nile virus.
And even if you've never seen mosquitoes near your home, experts recommend that you inspect your yard for eggs. The insects' eggs can last for years, waiting for the right conditions for hatching.
Aedes mosquitoes tend to lay their eggs along the waterline of flower vases, buckets and other containers that hold water. When they containers are filled up, the eggs get the water they need to hatch.
And hatching season is coming up, experts warn.
"It's a really good idea, especially going into the spring, that people do this survey now," he said.
I think there's a mosquito infestation near me. What should I do?
You should report black-and-white, daytime-biting mosquitoes to your local vector control agency. ("Vector" is a fancy word for something that transmits disease.) You can often get a free inspection and treatment when you report infestations.
At the bottom of this page on the agency's website, there is also a tool where you can locate your local vector control agency by entering your zip code.
Officials also recommend that you don't let water accumulate in your backyard, since mosquitoes breed in standing water. Get rid of buckets of water in your backyard, and drill holes in the bottom of pots and old tires so water doesn't accumulate.
"There's probably a million places to look," Fredericks said. "These mosquitoes can breed in as little as an ounce of water, or breed in a bottle cap."