BAGHDAD, Iraq (AP) - Jumping for joy, the 42-year-old mother of three hit the switch and screamed. "Electricity is here!" neighbors shouted, as women ran outside their houses to cheer, and men to shoot in the air.

Baghdad celebrated the beginning of the end Tuesday of a devastating 3-week-old power outage. But more than 80 percent of the city remained in darkness _ and doctors reported the first suspected cases of feared epidemics of cholera and typhoid, with no clean water yet running.

Fifty- to 60 percent of the children brought in for treatment at the city's Al-Iskan children's hospital were suffering from dehydration and diarrhea caused by bad sanitation and water, said Dr. Ahmed Abdul Fattah, the hospital's assistant director.

Doctors suspected hundreds of the children had cholera and typhoid, but with no labs fully working, and most U.N. health workers having fled, hard-pressed physicians said they could only treat the cases, not confirm them.

Despite a lack of power, water and phones _ in addition to shuttered shops, hours-long lines at gas stations and closed schools _ Baghdad's people on Tuesday showed signs of bouncing back from the U.S. invasion and the mob pillaging and burning that followed the collapse of Saddam Hussein's regime.

In crowded streets, pickups of families returning from wartime havens in the countryside scraped up against trucks ferrying oranges to market.

Some drivers reveled in the once-forbidden act of stopping on Baghdad's bridges over the Tigris River _ coming out of their vehicles to stare down into the lavish riverside palace compounds of Saddam.

U.S. soldiers stood guard at key installations with carnations stuck in their helmets, courtesy of Iraqi children tearing them out of flower beds.

Baghdad residents and the U.S. military have listed power as the capital's key need. Lights went off in Baghdad in the first week of April as bombs fell and frightened workers abandoned their posts _ or simply stayed home to guard them against robbers roaming at will in the darkness.

Residents across Baghdad have left their light switches flipped up for weeks _ waiting for electricity to return.

It happened late Monday and Tuesday in some west Baghdad neighborhoods _ sending men out in the street to fire AK-47s in elation.

"Thank God. We were living in darkness," said Yosra As'aad, a widow of 42.

As'aad and her oldest son, 18, sat home for three weeks in fear of robbers, going short of sleep to guard their home each night.

Each day, she measured out tap water for her youngest, a 7-year-old girl, leaving it to settle so the dirt could fall to the bottom. Without electricity, Baghdad's water purification plants had no means to operate.

As'aad greeted the return of electricity by flipping on each switch. Then, with Baghdad's summer coming, she ran to put bottles into the refrigerator.

"Cool water," she said, appreciatively.

"All of life depends upon electricity. All of life almost stopped," said baker Wisam Abbas, whose workers hauled loaves of bread out of ovens under bulbs lit in broad daylight, simply because they could be.

"During the bombing we were praying, and now for electricity we were praying," Mo'taz Khaleil said, strings of bare electric bulbs burning outside his egg shop.

All-Iraqi crews of electrical engineers by Tuesday had units at four power plants back up, said Jenan Behnam, chief engineer at Baghdad's key, southern electric plant.

That left 82 percent of Baghdad's homes still in the dark _ including Behnam's own, he said.

With a bit of luck, a fifth power plant revving up Tuesday would help light up 50 percent of the city by Wednesday, Behnam said.

Transmission lines snapped by shooting and bombing would slow full restoration of power after that, Behnam said, but near-full power still could be just days off.

Wartime damage and confusion largely caused the outage, power workers said: Fighting snapped a fuel line to the key plant, and destroyed the central office that coordinates the grid.

At al-Iskan children's hospital, doctors were praying for their overworked cluster of generators to hold on.

"Without them, these babies, 100 percent, would face death," Fattah said over the wizened, red faces of premature infants in incubators.

Other wards held listless children with sunken eyes. Some suffered from stomach infections caused by unclean water, draining fluids from their bodies. "An epidemic," Fattah said.

"We suspect it's cholera, but can't test, because we have no lab facilities left," said acting director Dr. Gassim Rahi Esa.

Doctors also were treating increasing cases of typhoid, the children's hospital said.

With clinics citywide depleted by looting, volunteers at both Sunni and Shiite Muslim mosques were treating typhoid and cholera cases out of clinics set up in mosque offices and wings.

With antibiotics for the infectious diseases running out, volunteer doctors at one Sunni mosque were routinely forced to split a single dose between two patients _ saving their lives, but increasing the resistance of the bacteria, Dr. Mosaab Abdul Wohab said.