BANGKOK -- Samroeng Verravanich wades through the rancid brown water in one of Bangkok's many flooded streets. The garbageman plunges a white-gloved hand into the filth, fishes out a slimy plastic bag and slings it into the red basket he's towing.
"If you have cuts, it can create infections between your fingers," Samroeng says of the dirty water, holding out a dripping hand peppered with a red rash. "My hands got infected. It hurts and it spreads too -- like a virus."
As Thailand's worst floods in more than half a century continue to creep into Bangkok, mixing with water bubbling up through drains and spilling over canals, many streets have become floating landfills. Plastic bags overflowing with waste and rotten food cling to boats, cars, motorbikes and people as they slowly snake through inundated roadways. Raw sewage and animal carcasses can be seen bobbing in waters ripe for disease.
No major outbreaks have been reported since monster monsoon rains spawned floods that began swallowing areas north of the capital in late July. But experts warn the biggest health threats will likely emerge in the coming weeks after moving floodwaters subside, leaving stale pools.
"There's a lot of danger around it," says Mark Thomas, a spokesman for UNICEF, which is assisting with sanitation issues. "You need to keep kids out of the water, and everybody should stay out of the water as much as possible."
Mosquito-borne diseases, such as dengue fever, are a concern as well as eye infections and waterborne ailments that can lead to diarrhea and severe dehydration.
Skin diseases and fungal infections are the flood's biggest plague so far, with nearly 100,000 cases of athlete's foot reported. Bouts of diarrhea and respiratory infections are also common, especially with many flood victims sheltering in hot, cramped sites that may not have electricity or clean water.
Some 110,000 people have been displaced nationwide and more than 400 killed, mostly from drowning, since the waters started inundating millions of farm acres before seeping into Bangkok on their way to the sea.
On Thursday, Bangkok's governor declared Bang Khae district in the west an evacuation zone, meaning residents in eight of the city's 50 districts have now been strongly urged to move their belongings to higher ground and leave.
Floodwaters have been spreading faster on the western side of the Chao Phraya river, which winds its way through the middle of the city, than the water creeping down the eastern bank toward the central business district.
Many submerged homes no longer have running water or working toilets, forcing remaining residents to bathe and defecate in the open, often in waters surrounding their homes. That waste can be spread into water where children play.
"We all know the risk is there," says Dr. Maureen Birmingham, World Health Organization country representative in Thailand. "People get water in their mouths that's contaminated with feces, and all the diseases that can ensue from that -- that's probably the biggest concern."
Since garbage trucks can no longer reach many hard-hit areas, brigades of trash collectors have started doing the work in boats or on foot.
On the same street where Samroeng and a colleague cleared rubbish in the northwestern Bangkok district of Bang Plad, 9-year-old Paradorn Junsamlee practiced swimming behind his mom. He smiled and plopped his chubby bottom down on the pavement with a splash, saying he had taken medicine to protect against disease in the floodwaters.
"I'm worried about him getting sick, but you can't stop him," says mother Nantana Junsamlee, a soaked T-shirt and shorts sucked against her skin. "I tell him, 'Every time you swim, you have to avoid getting water in your eyes and mouth."'
At a Buddhist temple down a nearby side street, dozens of stranded flood victims waited for a doctor to arrive by boat. One elderly woman says fast-rising waters forced her to flee without her diabetes medication. Another needed an injection for anemia.
Outside, two other flood threats were visible -- a 6-foot python held in a garbage can after it was caught near the shelter, and a fat 6-inch leech scorched on the temple's marble stairs by a cigarette lighter.
Thailand has a robust health infrastructure that extends from top-notch Bangkok hospitals that draw foreign medical tourists to an army of 900,000 community health workers who serve their neighbors in even the most remote villages. Childhood vaccination rates are high, which helps prevent fast-spreading diseases such as measles.
But even with all of that built-in support, Dr. Wiwat Wiriyakijja of Thailand's Health Ministry says he worries the worst may be yet to come.
While unloading boxes of medical supplies at the temple, he says cases of leptospirosis have already been reported. The waterborne bacterial infection, carried in rat and other animal urine, can seep into cuts through floodwaters and potentially kill if left untreated.
"I fear it as well," Wiwat says, adding that a doctor fell ill with the disease after treating patients in hard-hit Ayutthaya province, north of Bangkok. "It's very dangerous."
Samroeng, a 10-year veteran of the city's sanitation department, says he too worries about catching something from the fetid waters. He and his colleagues walk about 6 miles, seven hours a day, through water that can reach chest-high. They encounter syringes, fluorescent light bulbs that could explode and even chunks of human feces that must be bagged in plastic and taken to dry land for proper disposal.
"I cannot fear getting sick. Who wants to have these diseases?" he asks before wading father down the flooded street. "It's my job. It's my responsibility."