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The more we find out about Zika virus, the scarier it becomes

As winter turns to spring in the US and temperatures rise, mosquitoes are breeding again.

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We've watched the perplexing Zika virus, spread by mosquitoes, take hold of Latin America in the last several months. It's infected between 200,000 and 1.3 million people there, and while the disease is mild in most, it's been linked to birth defects and some other troubling neurological symptoms.

zika virus mosquito control
A municipal worker fumigates against the Aedes aegypti mosquito that transmits the Zika virus in Caracas, Venezuela. Fernando Llano/AP

Now that the threat of Zika could reach our shores, public health officials are ramping up the US response to combat the virus and the mosquitoes that transmit it.

It seems that the more we find out about Zika, the more concerning it becomes.

"Everything we look at with this virus seems to be a bit scarier than we initially thought," Dr. Anne Schuchat, a deputy director at the US Centers for Disease Control and Prevention, said at a press conference April 11. "And so while we absolutely hope we don't see widespread local transmission in the continental US, we need the states to be ready for that."

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What we do know

Zika microcephaly
Pietro Rafael, who has microcephaly, reacts to a stimulus during an evaluation session with a physiotherapist at the Altino Ventura rehabilitation center in Recife, Brazil. Ueslei Marcelino/Reuters

We've learned that the virus could be the cause of birth defects including microcephaly — a condition where babies are born with small heads that can lead to learning delays and other developmental problems. (Update: On April 13, the CDC said Zika is definitely the cause of microcephaly. The link had only been tentative before.)

This link to birth defects has centered the concern for infection around pregnant women, but babies aren't the only ones who could have complications.

Zika could be causing Guillain-Barre syndrome in adults, which is where the immune system attacks the body's nerves and sometimes causes paralysis. Most people recover from it after treatment, but symptoms like numbness and tingling can linger.

zika virus atomic level
An atomic-level microscopy image of the Zika virus. Purdue University/Kuhn and Rossmann research groups

Scientists also just reported cases of a rare infection called acute disseminated encephalomyelitis (ADEM) in a handful of patients who had Zika in Brazil. ADEM's symptoms are similar to multiple sclerosis, with vision loss and possible paralysis, but patients usually recover in about six months.

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Only about 20% of people get any symptoms when they get the virus, though, making Zika and its effects difficult to monitor.

People can also pass on the virus through sexual contact, though mosquitoes are the main transmitter.

Mosquitoes: public enemy No. 1

This spring, the mosquitoes that spread Zika could reach more US states than CDC officials originally thought. We know the Aedes aegypti species transmits the virus, and the Aedes albopictus species is a highly likely carrier.

If A. albopictus does spread Zika in the US, it could affect many more states — and highly populated areas — than A. aegypti. The CDC released these maps of the two species' ranges:

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cdc zika map graphic
CDC

Since we don't have a vaccine to protect against the virus or a drug to fight it, our best line of defense against Zika is to kill the mosquitoes spreading it.

Fortunately for most Americans, this feat will be an easier task in the US than it has been in Central and South America. We already have stronger mosquito control programs in place, and more people have air conditioning and screens, allowing them to keep mosquitoes out of their homes. Other mosquito-borne viruses that have already been transmitted on the US mainland, like dengue and chikungunya, have not wreaked havoc here the way they have in more tropical climates.

The Obama administration is trying to get Congress to approve $1.9 billion to fight Zika, which could support vaccine or drug development, though that will likely take many more months or years to achieve.

"This is a very unusual virus that we can't pretend to know everything about it that we need to know," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at the press conference. "The more we learn about the neurological aspects, the more we look around and say this is very serious."

CDC Public Health
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