Updated

Health workers are working to prevent outbreaks of measles and tetanus among earthquake survivors in Indonesia by starting a campaign of immunizations in the disaster zone, an official said Tuesday.

Health experts are concerned that the estimated 647,000 people displaced by the May 27 quake — a third of whom are living in makeshift shelters with no toilets or running water — are vulnerable to disease.

The government and the World Health Organization planned to begin immunizing all children under 5 in the quake zone against measles starting Wednesday, said Harsaran Pandey, a WHO spokeswoman. All adults in the quake zone will also receive a booster dose of tetanus vaccine, she said.

CountryWatch: Indonesia

"We are racing against time and disease after two people were reported with tetanus," said Gandung Hermanto, head of the surveillance division at the health department in Bantul, the worst-hit district.

Tetanus is an infection that usually originates from a contaminated wound, often a cut or deep puncture wound. It is fatal in more than 30 percent of cases, with even higher rates in the developing world.

As a woman grimaced in pain while a large cut was stitched up at a U.S. military field hospital, Lt. Eric Tausche said many victims suffered injuries that could easily lead to tetanus.

"It's a great concern anytime anyone comes here with an open wound," he said. "We've seen lots of compound fractures and soft-tissue damage. Everyone here with such an injury gets a tetanus shot."

More than 20 countries have contributed aid and personnel to the quake recovery effort.

The 6.3-magnitude earthquake in central Java island killed at least 5,857 people and injured 36,299 others, while leaving more than 130,000 homes damaged or destroyed, according to the government.

The U.N. Food and Agriculture Organization said $5.6 million is needed to help at least 100,000 farming families who had lost their livelihoods — part of a broader U.N. appeal for $103 million for quake relief over the next six months.

FAO said the farmers need seeds, fertilizer and farming equipment to resume work.

The money would also be used to replace livestock and repair damaged irrigation systems. But the FAO said harvesting still could be delayed and some crops completely lost.

Some 200 trucks, each loaded with more than four tons of rice destined for the disaster zone, left the city square in the ancient royal capital of Yogyakarta on Monday. Vice President Jusuf Kalla promised 22 pounds of rice per person each month until survivors' houses are rebuilt.

The international relief effort has picked up pace in recent days, although aid has yet to reach some remote areas.

Just north of the earthquake zone, the Mount Merapi volcano continued to spew lava and clouds of hot gases Tuesday, and officials warned of danger to nearby villages. Some scientists say the quake may have contributed to the volcano's increased activity.