In Ana Patricia Gomez Diaz's El Salvador, the government has advised women to avoid pregnancy for two years because of concerns about the Zika virus, but the mother of two with the kind smile was already pregnant and en route to the United States over a month before the alarm sounded.
Speaking at a shelter in southern Mexico in March, Gomez Diaz, now seven months pregnant, said she'd never heard of the virus, which health experts suspect can cause severe birth defects in babies born to mothers exposed during pregnancy.
El Salvador, along with other countries affected by Zika, has waged a campaign to inform and track pregnant women who may have been exposed to the virus. But like many migrants at the shelter in Ixtepec, an unfamiliar ailment and a hypothetical birth defect do not rate high on her list of concerns.
Here in the purgatory between her home and the one she hopes to make in the United States, Gomez Diaz has other things on her mind.
Such as taking care of her 4-year-old daughter in a shelter so crowded with hundreds of other migrants that at night the sidewalks are packed with dozens of sleeping bodies.
Or getting beyond the guilt of leaving her other daughter, who is 8, behind with the child's grandmother, and agonizing over how she will send enough money back when she arrives in the U.S. to make their separation worthwhile.
Or forgetting the gang that threatened to kill her when she wouldn't date a member of its ranks.
Or making it safely to the U.S. border without being kidnapped, raped or tortured.
Elsewhere in the Americas, Zika is prompting concern and fear. Scientists are studying whether the virus, which is transmitted by the Aedes aegypti mosquito, is responsible for children being born with small, misshapen heads, a condition known as microcephaly, which can lead to blindness, hearing loss and early death.
The U.S. Department of Homeland Security has said it will test pregnant women in its immigration detention centers and provide them with prenatal care. Most carriers of the virus are asymptomatic, and there's no simple exam that can be conducted at ports of entry to confirm the presence of the illness. Because microcephaly can't be detected before the end of the second trimester, pregnant women who have been exposed must wonder and wait.
At the Hermanos en el Camino shelter in Ixtepec, Gomez Diaz was one of four pregnant women in early March seeking respite before continuing a longer journey.
The shelter, founded by Father Alejandro Solalinde Guerra in 2007, each year houses as many as 15,000 migrants. Here migrants pass the time talking, playing dominoes, resting on mattresses or avoiding members of rival gangs from their home countries, as they wait for humanitarian visas or simply find food and shelter before continuing north.
The train tracks in the center of Ixtepec are littered with discarded supplies, the detritus of tens of thousands of journeys through one of the poorest regions of Mexico. Most migrants, fearing extortion and kidnapping, stick close to the shelter, never venturing far beyond the dusty road in front.
Carmen Elena Martinez Miranda, 20, from El Salvador, is almost five months pregnant. She left the capital, San Salvador, after a lack of opportunities and violence caused her to close down her humble business, a produce stand, and look for other options with her partner. In an effort to make money, she sells arroz con leche in the mornings, making about $6 a day.
She too had never heard of Zika.
Hilda Rosa Baca Garcia, 26, had made it to the shelter from Honduras with her boyfriend despite being six months pregnant. Her partner, who is missing one foot, made the journey on crutches.
After a childhood spent being passed between relatives who mercilessly beat and starved her, Baca Garcia speaks about her past blankly. She had heard of Zika but lumped it in with a number of other dangers and diseases, saying she heard it could cause fever and death but that in El Salvador injections were being administered. There is no vaccine or treatment for Zika.
Patricia Caballero, 29, left Honduras unaware that she was pregnant. She's spent her first trimester on the road and has lost more than 20 pounds as she's walked and gone without food, begging for water at ranches, occasionally bathing in rivers. Caballero was abandoned at 11 years old and left to care for four younger siblings, ages 9, 7, 5 and 3. "I loved them like they were my own children," she said.
"My little sister cried a lot every night, 'Mommy, mommy,'" Caballero said. She and her siblings tried to calm the child, and Caballero learned to fear losing control of her emotions.
"I always believe that God has given me the strength not to cry too much, because if I cry too much, I'm going to die of crying," she said. When Caballero told her story, she did so with a smile, still wary of letting herself break.
Caballero learned to cook and relied on the kindness of her neighbors as a child-turned-parent. Now, she is the one leaving behind her children — three of them, in the care of their paternal grandmother — but for very different reasons.
She's spent her life picking coffee, and she hopes her children will avoid the same fate if she can send enough money back for them to travel to the United States too. At least that's what she thought before she left. Then she slept in the mountains, hungry and dehydrated. Then she found herself facing the barrel of an AK-47 and turned over her few possessions to thieves shrouded in black.
"It's better that they wait there and study, that they don't come here," she said.
As for Zika? She had heard of it. It comes from a mosquito.
"I try not to let them bite me much," she said, her eyes shimmering, her lips, as ever, smiling.
Tillman is a special correspondent.