HAVANA (AP) — Cuba is warning of high mosquito concentrations and asking islanders to help stamp out potential breeding grounds to fight the spread of infectious diseases, amid rumors of serious dengue and yellow fever outbreaks.

Sternly worded reports in state-run media and on TV newscasts said there is an unfounded "low perception of risk" among Cubans, despite a noticeable increase in mosquito populations in 23 municipalities.

Juan Ramon Vazquez, the Public Health Ministry's national antiviral director, urged islanders to be vigilant and get rid of standing water, saying the heat, humidity and rains of the Cuban summer create ideal conditions for mosquitoes to proliferate.

The threat is most critical in the 15 municipalities of Havana and in eight provincial capitals, Vazquez said.

It's typical for cases of infectious disease to increase cyclically during the rainy season, and the government periodically ramps up campaigns to remind people about the danger of letting standing water, high weeds and garbage accumulate.

So-called "bazooka" brigades go door-to-door noisily fumigating homes and sealing uncovered water tanks, while local media name and shame businesses where mosquito larvae are found. A regular TV program whose title translates roughly as "hitting hard with the gloves off" gives tips for controlling the insects.

There have been rumors and unconfirmed reports of bad outbreaks of dengue and yellow fever this summer. Some foreign media reported one death from dengue this week, citing anti-government dissidents whose accounts could not be independently confirmed.

The government generally stays silent about infectious disease cases and especially any deaths, though earlier this summer it acknowledged a cholera outbreak in eastern Cuba that killed three senior citizens and sickened 158 people, according to official numbers.

Authorities said the outbreak was brought under control.