The Centers for Disease Control just added 4 more countries to the list of places with Zika

The Centers for Disease Control and Prevention has added four more countries around the world to its list of territories with local transmission of the Zika virus.

The Zika virus, which is mainly transmitted by mosquitoes, has been spreading around the world since 2015. Once infected, only about 20% of people ever show symptoms, which most commonly include fever, rash, joint pain, and red eyes.

The countries that have joined the list of places with mosquito-transmitted Zika are:

• Angola
• Guinea-Bissau
• Maldives
• Solomon Islands

It's the first time since November 2016 that the CDC has updated its list of countries with local transmission. (The last additions were Palau and Montserrat.) Here's the list of all the current places with the virus. 

The main reason Zika is troubling is that it is a cause of birth defects, including microcephaly - a condition where a child is born with an abnormally small head - in babies whose mothers have had Zika. The virus has also been linked to a neurological condition called Guillain-Barré syndrome.

In November 2016, the World Health Organization said Zika was no longer an international public health emergency. "We are not downgrading the importance of Zika, by placing this as a longer program of work, we are sending the message that Zika is here to stay," Dr. Peter Salama, executive director of WHO's Health Emergencies Program said at the time.