By Tom Gibb BBC Brazil correspondent

More than 50,000 health workers, firemen, troops and volunteers have started a campaign in Rio de Janeiro to try to stop Brazil's worst recorded dengue epidemic.

So far at least 70,000 people have come down with the disease and 28 have died in Rio de Janeiro state.

This is serious, my daughter's had dengue, my maid's son and two of my students have contracted dengue. It's no joke, we have to do something

Ana Luisa Nascimento volunteer

The epidemic has also spread to at least seven other cities in Brazil.

They are calling it "D-Day" - the start of a war against the mosquito which carries the dengue virus.

As the Health Minister, Barjas Negri, opened the campaign, waving a test tube with a mosquito in it, the thousands of volunteers, soldiers, firemen and others took to the streets.

The idea is to mobilise millions of residents to get rid of all the stagnant water where the mosquitoes breed.

Widespread cases

In one Rio suburb, residents marched through the streets with giant rubber mosquitoes. In other areas, volunteers handed out leaflets and went from house to house.

Many experts believe the official figure of some 70,000 cases is a huge under-estimate as most cases are not reported.

The drive to inform has reached Rio's shanty towns

Dengue causes high fevers and severe muscle pains but does not usually kill.

However, the 28 deaths in Rio were mostly caused by a virulent variety of the disease called haemorrhagic dengue.

Earlier this week the government said it had spent almost $250m on combating the epidemic.

But there has been widespread criticism of government spending cuts in recent years in which thousands of health workers were laid off. Many of them have held protests, demanding their jobs back.

The health minister said he expected the D-Day campaign in Rio would bring the epidemic under control within the next month.