RIO DE JANEIRO, Brazil (CNN) -- The death toll in flood-ravaged southern Brazil has reached 116 and the first cases of a water-borne, potentially fatal disease are being investigated, the nation's Civil Defense agency reported.
People use a boat to navigate flooded streets in the Brazilian state of Santa Catarina last week.
The number of missing residents has increased to 31, the agency said. The previous tally was 19.
Nearly 79,000 residents have been left homeless, many of them in the hard-hit state of Santa Catarina.
Many of the deaths have been caused by mudslides.
Officials are now worried about disease, as 10 cases of leptospirosis are suspected, the state news agency reported.
Leptospirosis is an infection in rodents and other wild and domesticated animals, according to the World Health Organization. In humans, exposure through water contaminated by urine from infected animals is the most common form of infection. The disease is often found in flooded areas.
Ten people with symptoms are being treated in the cities of Blumenau and Ilhota, the state-run Agencia Brasil reported.
Symptoms usually occur 2 to 30 days after infection and consist of high fever, malaise, sharp and constant headache, intense muscular pain, fatigue and chills. Nausea, vomiting and diarrhea also are common. About 10 percent of patients develop jaundiced eyes after the third day, indicating the most severe cases.
Authorities also were warning residents in flooded areas to be careful with food and water they consume. Food that has been under water or moist should not be eaten unless it's in a sealed plastic bag or a can, officials said.
The health secretary for Santa Catarina said residents who drink contaminated water also run the risk of getting hepatitis A and diarrhea.
Rescuers also are at risk of disease and injury.
In the city of Maximus in Luis Alves state, eight rescuers were injured over the weekend, one of them gravely, Agencia Brasil reported.
Brazilian President Luiz Inacio Lula da Silva said Monday that Santa Catarina will be rebuilt and become just as strong as it was.
"We cannot lose hope," Lula said. "We must be convinced that people will reconstruct the state of Santa Catarina. There is a national solidarity never seen before in the history of the country."
Lula flew over some of the flooded areas last week and proclaimed the disaster one of the worst in the country's history.
"I've never seen anything like this," he said Thursday.
He said last week he was releasing 1.97 billion Reals (more than US$850 million) in aid to the afflicted areas.
Officials have distributed 880 tons of food, nearly 1 million liters of water and 60 tons of clothing, toys and cleaning and personal hygiene material, Agencia Brasil said Monday.
The Civil Defense said seaplanes have flown 548 relief missions in seven days.
The disaster also is having an economic effect, with bridges, roads, houses and buildings destroyed. The Federation of Industries said the closed port in Itajai is costing $33 million a day. The port is the major terminal for frozen goods in Brazil and second in the transport of containers, Agencia Brasil said.
Port Superintendent Arnaldo Schmitt said last week part of the terminal could be back in operation in two weeks.
Weather conditions may not allow that to happen, though.
The Civil Defense issued an alert Monday for heavy rains in 14 states and the federal district.