By the numbers: Zika virus in the U.S.

Zika virus, the global public health emergency suspected of causing birth defects, has arrived on America’s shores.

Though mosquitoes aren’t carrying or spreading the disease here, 258 people, including 18 pregnant women, have been diagnosed with Zika virus in the United States since the beginning of this year, according to the federal Centers for Disease Control and Prevention.

Americans who were infected had either traveled to one of the dozens of countries with outbreaks or had sex with someone who’d visited those places. At least one case was an infant born with microcephaly whose mother traveled to a country with an outbreak while pregnant.

Zika cases have so far been reported in 34 states, with the most in these states:

• Florida: 59 cases
• New York: 42 cases
• Texas: 34 cases
• California: 13 cases

The CDC hasn’t yet released detailed data on everyone who returned home with Zika virus through the middle of March. But the agency did recently provide information about the 116 Americans who’d been diagnosed with Zika as of the end of last month.

Of those, 110 had visited countries in these regions before contracting the Zika virus:

That’s quite different from what’s been seen locally. Nearly 50% of those tested for Zika virus in Los Angeles County had traveled to Mexico, according to Dr. Rachel Civen, a medical epidemiologist with the county’s Department of Public Health.

So far, there have been four Zika cases confirmed in L.A. County, including at least one pregnant woman. The rest of California’s Zika cases this year have been in these counties, from north to south: Yolo, San Joaquin, Contra Costa, San Francisco, Santa Barbara, San Bernardino, and Orange.

“With the current CDC backlog of testing, it is expected the number of U.S. cases, as well as Los Angeles County, as well as California cases will be increasing,” Civen said in a recent webinar for local physicians.

According to the CDC, 98% of Americans diagnosed with Zika virus had at least one symptom. Here’s a breakdown of how many people -- of the 115 travel-associated cases, excluding the newborn, as of the end of last month -- reported experiencing each symptom:

For most people, Zika virus is a mild illness, with symptoms lasting less than a week.

But there’s increasing evidence that pregnant women who contract the illness can infect their fetuses, causing birth defects. Pregnant women have been advised not to travel to countries with outbreaks.

In the United States, nine pregnant women have been diagnosed with Zika virus, according to the CDC. Two had miscarriages, two had abortions, two gave birth to healthy babies, one gave birth to an infant with microcephaly and two were still pregnant as of the most recent CDC update.

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