Eleven days after news broke that an unknown disease had killed eight people in the city of Maracay, Venezuela, doctors have concluded that the deaths were caused by chikungunya, a mosquito-borne virus. Meanwhile, Ángel Sarmiento, the doctor who first announced the deaths, has fled the country after being accused of terrorism by President Nicolás Maduro.

Although officials initially speculated that the deaths were caused by an unknown hemorrhagic fever, six of the eight original fatalities tested positive for chikungunya when samples were analyzed in nongovernmental labs, says Julio Castro, the health minister of the municipality of Sucre and a professor in the Institute of Tropical Medicine at the Central University of Venezuela (UCV). “We don’t think these deaths are due to an unknown or rare disease,” he told ScienceInsider, adding that “I have no doubt” that chikungunya is responsible.

After arriving in the Caribbean late last year, chikungunya has been sweeping the Americas. As of 19 September, the Pan-American Health Organization reported 729,178 suspected and 9537 confirmed cases in the region. There is no vaccine or cure for the disease, which is similar to dengue fever and causes joint pain. It is fatal in about one in 1000 cases.

Maracay’s cluster of nine fatalities, reported between 30 August and 15 September, has raised questions about exactly how many people are infected. The deadly cases are “the tip of the iceberg,” Castro believes. In a press conference on Monday, Castro and two other health professionals—Gustavo Villasmil, health minister of the state of Miranda, and Manuel Olivares, a doctor at UCV’s hospital—estimated that between 65,000 and 117,000 people in Venezuela are infected with chikungunya. They reached that figure by using World Health Organization standards for calculating the spread of epidemics. But it is dramatically higher than the official tallies released by Venezuela’s federal health ministry, which recognizes just 398 cases of chikungunya and three deaths.

Many infectious diseases, including malaria and dengue, are on the rise in Venezuela, where the public health system has been crippled by a lack of funds and medicine (including antifever drugs that can help treat the symptoms of chikungunya). Sarmiento’s comments about the deaths in Maracay appear to have been the straw that broke the camel’s back when it came to criticism of the government’s public health record, Villasmil says. Now facing prosecution, Sarmiento fled to an undisclosed location in Central America. Villasmil and Castro remain in Venezuela but have left their homes after participating in the press conference, as a precaution against retaliation.