Paraguay has declared a 60-day state of emergency to deal with an outbreak of dengue fever which has killed at least 10 people in the past two months.
Hospitals may not be able to cope if cases go on rising, doctors say
Officials say 14,654 people have been diagnosed with dengue.
But doctors say the figure is 10 times higher, and are worried about a new more virulent variant of the disease.
Brazil and Bolivia have also seen a rise in cases of dengue, which is spread by mosquitoes and is endemic in much of the Americas.
Dengue fever causes severe headaches, as well as muscle and joint pain.
The Paraguayan Health Minister, Oscar Martinez, says blood samples from some of the dengue victims are being sent to the United States and Argentina so that different variants of the disease could be identified and the correct treatment given.
Doctors in Paraguay say that at least five of those who died were suffering from a particularly virulent variant of the disease called "gastric dengue", never seen before in the country.
Transmitted by mosquitoes
Symptoms of the severe, flu-like illness include severe headaches, fever, rash, joint pains
Seldom deadly, but has potentially lethal variants
Dengue fever is found in Africa, South-east Asia and China, the Indian sub-continent, the Middle East, South and Central America, the Caribbean and Australia
Gastric dengue attacks vital organs - such as the liver, heart, lungs or brain - and can cause death within hours.
Other patients died of dengue haemorrhagic fever, a variant which can lead to enlargement of the liver, and in some cases, circulatory failure.
Doctors working in state-run hospitals are planning to hold a demonstration outside the health ministry on Friday, in protest at what they describe as government inefficiency.
Private-sector doctors have accused the authorities of underestimating the impact of the outbreak, saying official figures represent 10% of real cases.
Specialists have warned that public hospitals do not have enough intensive-care capacity to cope if the number of severe cases continues to rise.
However, the National Emergency Secretary said the country's health system was not being overwhelmed by the outbreak.
Aristides Gonzalez said special brigades would target mosquito breeding-spots - such as stagnant water pools and rubbish dumps - in homes and public places.
Experts have blamed the unusually rapid spread of the disease on a higher rainfall and uncommonly warm weather, which have boosted the population of the aedes aegypti mosquito.
More rains and high temperatures are forecast for the next two months, prompting fears that the number of cases will continue to rise.