Because while they lived with the fear of death, she was in the business of life.

She stopped at the next residence where a child's wailing could be heard from inside. A once colorful wool blanket now made gray by the dirt that attacked it like a cancer covered the doorway. A clay flowerpot sat outside with a single yellow sunflower. She spit dirt then called out to the woman of the house.

"Maria!"

A hand yanked the blanket aside, and the distressed face of a young woman appeared in the doorway. Maria Teresa Castillo was only twenty-three years old, but she looked twice her age. Life in the colonias aged a woman. Maria was a Mexican national and a single mother of four children and pregnant with her fifth. The youngest had diarrhea. From the river water.

" Senora, thank God you have come," Maria said in Spanish. "Benita, she is very sick."

She stepped inside and recoiled at the foul smell of the child's stool, suffocating in the small space. She blew out a breath against the odor then waited a moment for her eyes to adjust to the dim light. Electricity had not yet come to this colonia. She now saw the small child lying on a burlap pad on the dirt floor and crying against the pain of intestinal cramps.

"Maria, you cannot bathe her in the river," she said in Spanish. "The parasitos and toxins in the water make her sick."

The Rio Grande was contaminated with industrial waste from the maquiladoras on the other side and human waste from both sides. She cleaned her hands with a gel sanitizer then dropped the satchel and knelt beside her two-year-old patient. She placed her palm on the child's forehead; her skin felt hot and clammy. She retrieved the tympanic thermometer from her coat pocket, placed a disposable cover over the probe, then inserted the probe into the child's ear canal and took her temperature.