With the death toll from last week's devastating tsunami in South Asia nearing 150,000, relief workers are warning that number could soar unless survivors get access to clean water and supplies.

Rain and animals slowed relief efforts in some parts of south Asia on Tuesday. The main airport at Indonesia's Sumatra Island was closed for much of the day after a relief plane hit a water buffalo on the lone runway. No one was hurt, but the closure highlighted the vulnerability of the relief effort.

With roads and harbors along the Sumatra coast destroyed by the tsunami, helicopters are

LT. Commander Mark Leavitt

playing a vital role delivering supplies to the hardest hit areas.  U.S. Navy Lt. Commander Mark Leavitt said the survivor's desperation is apparent as they rush to grab badly needed supplies. "I was afraid that someone was going to run underneath us, or get small children blown away or something like that," he said.

Collin Powell (front) and Jeb Bush (rear) visit Thailand

Meanwhile, U.S. Secretary of State Colin Powell got his first close-up look at the heavy damage from last week's tsunami when he visited the Phuket resort area in Thailand. He later traveled to Indonesia where he promised the U.S. commitment to help was not just a one-time humanitarian effort. "This has to be a long-term reconstruction and rehabilitation effort, to rebuild homes, and rebuild families, and rebuild lives. And you can count on the United States being with you for this longer, rebuilding period," he said.

Elsewhere, health officials from Indonesia to Sri Lanka warned there was an ever-increasing threat of diseases such as cholera and malaria breaking out among the 5-million who have been displaced by the disaster. Many of the survivors are still without clean water and sanitation.

In Sri Lanka, heavy rain in some parts of the country, slowed relief efforts, even as the first

US and British Marines arrive to provide relief

contingents of U.S. and British Marines began arriving with helicopters and other heavy equipment. 

As hope fades any more survivors will be found, some semblance of normalcy returned to parts of the affected region. In Thailand, children at this school resumed classes, mourning their own losses, a teacher and a student killed by the tsunami.