Among the problems facing Haitian earthquake survivors is the shortage of clean water.
If survivors go without water, they could die of dehydration. Those desperate enough to drink dirty water risk getting diarrheal diseases, including cholera.
International aid teams are working to alleviate the problem, which is familiar to those with experience in disaster zones.
The United Nations Children's Fund has shipped water purification tablets, water tanks and rehydration salts to Port-au-Prince. The World Food Program is also distributing water purification tablets.
A U.S. aircraft carrier now operating off Haiti's coast also brought thousands of bottles of water and is equipped with purification machinery capable of producing more than 1.5 million liters of drinking water a day.
Aid workers' ability to distribute the supplies has been hampered by transportation and communication difficulties.
Clean water was already scarce in Haiti before the earthquake hit. The World Health Organization says that as of 2006, only 58 percent of the population had regular access to clean water, and only 19 percent had appropriate sanitation.
The head of the U.S. Agency for International Development, Rajiv Shah, said the U.S. military will provide 100,000 10-liter water containers.
Non-governmental organizations are also helping. Water Missions International, a U.S.-based charity, has sent 10 water filtering systems to Haiti and is planning to send more. The systems can provide clean drinking water to thousands of people a day.
Some information for this report was provided by AP and AFP.