There's a new virus called Zika spreading in South America, and on Monday it was declared a "public health emergency of international concern" by the World Health Organization, officially establishing it as a serious threat.
Zika, which has no cure, has been documented in the United States, but only among travelers. And itmay be linked with two more serious complications:
- A dangerous birth defect known as microcephaly
- A rare but often temporary disorder where the immune system attacks its own nerve cells
Here's a rundown of the good and bad news about the virus.
First, the good news: Zika israrely fatal (no deaths have yet been documented in people with Zika virus and no other illnesses). Symptoms of the virus are similar to those of a cold or fever.
And the bad news: It may be linked with a dangerous birth defect known as microcephaly, where babies are born with abnormally small heads. The CDC is also working to determine if there may be a link between Zika and Guillain-Barré syndrome (GBS), a rare disorder where your immune system attacks itself, damaging the nerve cells and leading to muscle weakness and occassionally paralysis. In general, symptoms of GBS last anywhere from several weeks to a few months. Most people fully recover, but others may have permanent damage. In rare cases, it can be fatal.
But that's not the worst news with Zika: There's also no rapid diagnostic test to detect the virus in a newly-infected person, and only about 1 in 5 infected people ever shows symptoms.
Last week, World Health Organization officials said the virus was “spreading explosively” in the region and President Obama voiced his concerns for the Zika virus here in the US, calling for more research into ways to stop the spread of the disease.
This is not the first time the alarm bells have been sounded. Earlier in January, Peter Hotez, Dean of the National School of Tropical Medicine at Baylor College of Medicine, told NBC Newsthat he was "very worried about Zika."
Hotez, who's also the Director of the Texas Children's Hospital Center for Vaccine Development, said that while a single tourist is unlikely to be the cause of an outbreak here, some American cities could be vulnerable to Zika's spread.
"We have to act now," Hotez said.
The problem with Zika: Low-level symptoms and potentially serious consequences
Hotez added that one of the biggest issues with the Zika virus, which is spread by a certain species of mosquito called Aedes aegypti, is that it "tends to produce low-level symptoms." They include fever, rash, join pain, and red eyes. But there's a bigger problem, too: Once infected, only about 20% of people with Zika ever show those symptoms, according to the CDC. Plus, the illness is typically mild — symptoms usually last anywhere from several days to a week, and hospitalization is rarely necessary.
But the virus, while not necessarily damning in and of itself, has been linked with a far more concerning problem: babies born with abnormally small heads, a serious condition known as microcephaly. After some mothers showed symptoms of the virus during their pregnancy, their babies were born with the condition.
Since the outbreak of the Zika virus in April 2015, Brazil has documented 4,180 cases of the condition in babies born to women who were infected during their pregnancy — 20 times the rate of the previous year and a 7% increase from the number recorded just last week.
Still, scientists can't say for sure what the link is between Zika virus and birth defects.
"We know very little about how Zika virus infection occurs during pregnancy and how it causes birth defects," Dr. Yoel Sadovsky, Director, of the Magee-Womens Research Institute and a professor of obstetrics, gynecology, and reproductive sciences at the University of Pittsburgh told the Genetic Expert News Service.
Based on research on how other viral infections behave during pregnancy, Sadovsky added that "several steps" are likely needed for a virus to affect the fetus and most likely include crossing the placenta, the organ that connects a developing fetus to a mother's uterine wall and allows the fetus to take in nutrients.
Where the virus is now
So far, the disease has been identified in a number of states in people who recently traveled to areas where the virus is being transmitted locally. Local transmission of the virus, which is spread by mosquitoes, has been documented in Puerto Rico and the US Virgin Islands as well.
Here are the 24 countries and territories where the virus had been transmitted locally as of Wednesday:
In the US, no local transmission of the virus has been documented yet — so far it has only been diagnosed in people who've recently traveled to places where it is being transmitted locally.
What you need to know about Zika in the US
While there has not been any local transmission via mosquitoes in the US yet, the WHO has previously warned of this possibility. Zika is spread by Aedes aegypti mosquitoes, which are prevalent in many American countries and thrive in tropical climates. This is why experts like Hotez have warned of it popping up in areas in the US with wet lowlands, warm temperatures, and species of mosquito that can transmit the virus.
"I am quite worried about Zika taking off on the Gulf coast," Hotez told NBC News.