In Cambodia, Va Ling, 12, holds a portrait of his mother at her funeral pyre; the picture is part of the “World Free of TB” exhibition at the United Nations.

Medics with a wounded marine in Iraq, included in “The Sacrifice,” a show at 401 Projects in the West Village (photo James Nachtwey)

Lek, a patient with AIDS and tuberculosis, in Thailand. Tending to her is Father Michael Bassano, whose hand is seen, lower right. This picture is part of “World Free of TB,” an exhibition at the United Nations (photo James Nachtwey)

Derek McGinnis, who lost a leg in Iraq, tries surfing for the first time, in Pismo Beach, Calif., October 2006. The photograph is part of James Nachtwey’s “Sacrifice” series (photo James Nachtwey)

“The Sacrifice” runs through April 24 at 401 Projects, 401 West Street, at Charles Street, West Village, (212) 633-6202. “World Free of TB” runs through April 27 in the visitors’ lobby of the United Nations, First Avenue at 46th Street, Manhattan, (212) 963-0089. (Closed on April 6.)