Lost in much of the media coverage of new domestic cases of chikungunya, a painful and sometimes debilitating mosquito-borne virus, is that Mexico has been experiencing an alarming rise in infections.

That means this virus could potentially spread across the porous border–and there is already evidence of at last one case arriving from Mexico.

In May, the Centers for Disease Control and Prevention added Mexico to the “Watch Level 1” category for the disease. Last week, the CDC updated their “Level 1” warning, advising travelers to Mexico to “protect themselves from chikungunya by preventing mosquito bites.”

Local transmission began in Mexico in October 2014, with 155 cases confirmed before the end of the year. The numbers skyrocketed this year, with 9,952 cases reported in Mexico as of November 8.

According to CDC data, the U.S. this year has seen 571 chikungunya cases in 42 states as of November 17, with all reported cases coming from “travelers returning from affected areas.”

There is immediate cause for concern about the spread of the disease domestically, due to the increased detection of yellow fever mosquitoes–also known by their scientific name, Aedes aegypti–in California over the past year. The aggressive mosquito is one of the insects capable of transmitting chikungunya, as well as the deadly dengue hemorrhagic fever and other serious diseases.

The news media has spotlighted chikungunya in recent days after a study released last week found the disease can cause severe and potentially fatal brain infection, especially in infants and seniors.  The report, published in the journal Neurology, examined a 2005-2006 chikungunya outbreak on Reunion Island in the Indian Ocean. Scientists found that the rate of encephalitis among those infected with the chikungunya virus outpaced the rate for all encephalitis reported in the U.S. from 1998 to 2010.

The most common symptoms of chikungunya are fever and joint pain. Other symptoms include headache, muscle pain, joint swelling, or rash.

Much of the news media reported the disease largely originates in the Caribbean as well as Central and South America, failing to document the outbreak across the southern U.S. border.

NBC News reported on chikungunya last week:

The virus only arrived in the Western Hemisphere in December 2013, on St. Martin. But it spread fast and has been found as far north as Florida and across Central and South America.

Source: EXCLUSIVE: Media Minimize Mexico’s Role in Spread of Debilitating Virus Hitting U.S.