Authorities in Mexico's Pacific resort of Acapulco are fumigating streets and homes to combat an outbreak of the mosquito-borne chikungunya virus, but some crime-weary residents refuse to open their doors.

The state of Guerrero, where Acapulco is located, has reported more than half of the chikungunya cases found in Mexico this month, according to the health ministry.

Most of Guerrero's infections have been detected in Acapulco, prompting authorities to deploy 550 health officials and 62 vehicles with fumigating sprays to kill .

The city is conducting lab tests on some 2,000 people with symptoms of the virus to see if they have chikungunya.

"The rains of May are coming, so homes must be clean to avoid water accumulation and the proliferation of mosquitoes. This is what we fear," said Cornelio Bueno, deputy secretary of the state's disease control and prevention department .

Officials said the at-risk areas in Acapulco are outside the tourist zone, in the rougher neighborhoods that have been hit by drug gang violence and other crimes.

Five percent of the 300,000 families whose homes have been fumigated in the past are refusing to open their doors again over fears that criminals could rob them, said Rufino Silva, another state health official.

"It's because of public safety, seeing how things are at the moment," said one fearful woman living in the dangerous Renacimiento district.

The virus—rarely fatal, but nevertheless serious—sparks high fevers and severe joint aches, as well as headaches, nausea and extreme fatigue.

It has spread across the Caribbean, to Central America and South America. There is no vaccine or treatment.