Infectious diseases are spreading in densely populated makeshift camps as thousands of amputees strain medical capacity in Haiti after the devastating earthquake.

The World Health Organization (WHO) said on Friday that the number of patients affected with diarrhea, rubella and tetanus in Haiti are on the rise.

"Medical teams have reported of an increase in cases of diarrhea in the past three days," WHO spokesman Paul Garwood said at a press conference.

He added that there were also increased reports of rubella and tetanus in densely populated areas.

Together with the Haitian government and the United Nations children's fund UNICEF, the WHO will launch a vaccination campaign next week.

It is estimated that before the 7.3-magnitude earthquake on Jan. 12, only 58 percent of Haitian children were vaccinated.

Garwood said that there had been a severe shortage in medical personnel, especially doctors specializing in orthopedic surgeries and related treatment amid a rising number of amputees.

According to Garwood, some 2,000 amputations have been performed after the earthquake.

Aid groups estimated that the total number of amputees due to the earthquake could run into tens of thousands, and their care would burden the country's medical system for decades.

Physical rehabilitation is expensive. The amputees, many of them children, will need more than one prosthesis for lost limbs -- a burden hardly bearable for the impoverished nation.

Life remains hard for survivors more than two weeks after the quake, which killed up to 200,000 people. Food supplies are far from enough for everyone, and antibiotics and other urgently needed medicines are out of reach for many.

"In this phase of reconstruction, we are going to need a lot of resources -- human, material, financial," said Ecuador's President Rafael Correa while visiting Haiti on Friday.

Correa visited Haiti as a representative of the Union of South American Nations (UNASUR), a regional organization he currently chairs.

Haitian President Rene Preval criticized a lack of coordination for international aid to his country after a meeting with Correa.

Many countries, such as Germany, the United States and France, have bypassed the Haitian government in channeling assistance through their own institutions, he said.

Despite all the difficulties, life was slowly returning to normal with more shops opening and banks resuming operation in downtown Port-au-Prince.

Students would also be able to return to school on Monday, said an official of the UN Office for the Coordination of Humanitarian Affairs (UNOCHA).

Relief agencies and the Haitian government were working together to ensure classes would resume on Monday, UNOCHA Public Information Officer Kristen Knutson told Xinhua.

The quake has damaged 5,000 to 8,000 schools across the country, affecting some 1.8 million students, Knutson said.