BATON ROUGE, La. -- Volunteer physicians are pouring in to care for the sick, but red tape is keeping hundreds of others from caring for Hurricane Katrina survivors even as health officials worry about potential outbreaks.

Among the doctors stymied from helping out are 100 surgeons and paramedics in a state-of-the-art mobile hospital marooned in rural Mississippi.

"We have tried so hard to do the right thing. It took us 30 hours to get here," said one of the frustrated surgeons, Dr. Preston "Chip" Rich of the University of North Carolina at Chapel Hill. That government officials can't straighten out the mess and get them assigned to a relief effort now that they're just a few miles away "is just mind-boggling," he said in a phone interview.

While the North Carolina doctors waited yesterday, the first predictable signs of disease from contaminated water emerged on Saturday.

A Mississippi shelter was closed after 20 residents got sick with dysentery, probably from drinking contaminated water.

However, the country's leading health official told The Associated Press in an interview at a triage center yesterday that her biggest concerns are tetanus and childhood diseases.

"Tetanus is something we'd be especially concerned about," said Dr. Julie Gerberding, head of the federal Centers for Disease Control and Prevention. Tetanus lives in soil and can enter the body easily through a scratch, and many flood survivors have endured filthy conditions.

Gerberding also urged health care workers in the growing multitude of refugee shelters to try to find out a child's shot history and, "If you can't establish that a child has been vaccinated, then vaccinate. We can't take chances."

Diseases such as measles and whooping cough could rapidly spread in the cramped quarters, which thousands of flood victims are now sharing.

So far, there have been relatively few cases of diarrhea and infections, Gerberding said, but "we're early in the process."

The CDC chief, who traveled to Louisiana with Health and Human Services Secretary Michael Leavitt, Surgeon General Dr. Richard Carmona and other top health officials, spoke with the AP after visiting an impressive triage center on the basketball court at Pete Marovich Center at Louisiana State University.

Next door in Mississippi, the North Carolina mobile hospital waiting to help also offered impressive state-of-the-art medical care.

It was developed with millions of tax dollars through the Office of Homeland Security after the Sept. 11, 2001, attacks.

With capacity for 113 beds, it is designed to handle disasters and mass casualties.

Equipment includes ultrasound, digital radiology, satellite Internet, and a full pharmacy, enabling doctors to do most types of surgery in the field, including open-chest and abdominal operations.

It travels in a convoy that includes two 53-foot trailers, which yesterday afternoon was parked on a gravel lot 70 miles north of New Orleans because Louisiana officials for several days would not let them deploy to the flooded city, Rich said.

Yet plans to use the facility and its 100 health professionals were hatched days before Hurricane Katrina devastated the Gulf Coast, doctors in the caravan said.