What's behind the fall in malaria deaths?

A new World Health Organization (WHO) report released on Wednesday showed a significant number of countries are moving towards the elimination of malaria with millions of deaths averted and millions in healthcare costs saved.

The mosquito-born disease is widespread in tropical and subtropical regions of the world, including Africa, Latin America and Asia. In 2000, the United Nations set itself a target to halt the rising number of cases of malaria as one of its "Millennium Development Goals."

Across Africa, where as many as 90 percent of deaths from malaria have occurred, death rates have fallen by 66 percent over the past 15 years and by 71 percent among children under five.

The WHO report cites six main interventions that have helped reduce the spread of malaria.

Insecticide-treated mosquito nets (ITN)

Since 2000, there's been a huge effort to encourage people in malaria-prone areas to sleep under insecticide-treated mosquito nets (ITNs). Dip-treated using a synthetic pyrethroid insecticide, some reports suggest ITNs are twice as effective as untreated nets.

NGOs say more than 200,000 million nets are needed in sub-Saharan Africa each year.

The WHO estimates that in Africa more than 50 percent of the most at-risk population now sleeps under ITNs.

Health experts say the number of children under 5 who sleep under nets is very encouraging. But overall coverage remains patchy, with just 20 percent of at-risk people sleeping under them in some countries.

Despite their effectiveness when used, many analysts say hot and humid climates make for an uncomfortable night's sleep under nets.

Indoor residual spraying

Insecticide is sprayed on the walls of buildings to prevent the spread of malaria. It works best on porous materials such as wood and mud, and is most effective if the whole neighborhood is sprayed.

But experts say the number of homes treated is not widespread and has been falling in recent years because it is unpopular.

Larval control

This includes the "fogging" or spraying of neighborhoods in high populated areas with insecticides. Water reserves where mosquitoes breed are targeted in particular.

Around 48 at risk countries use one of the many larval control techniques available to prevent large mosquito populations taking hold in the first place.

Preventive therapies

These drugs are targeted at preventing malaria in infants, schoolchildren and pregnant women.

In at risk countries, as many as 52 percent of expectant mothers were given at least one dose of preventive therapy in 2014. The WHO recommends they receive at least three doses.

Some health agencies have been piloting the first malaria vaccine, a four dose treatment offered to children.

During a 4 year study, in children aged 5-17 months, use of the vaccine led to a 39 percent efficacy against malaria and a 31.5 percent efficacy against serious cases of the disease.

Final trial data published in the Lancet earlier this year showed the effectiveness remained for up to 4 years after vaccination.

The WHO is now attempting to get funding to extend the vaccine pilot program across many countries.

Diagnostic testing

Over the past 14 years, there's been a significant improvement in the number of people formally diagnosed with malaria, either by microscopy or a rapid diagnostic test.

According to the report, South-East Asia and India carry out the most diagnostic tests each year, improving treatments for those struck down by the disease.

In Africa, the number of people tested for malaria has increased from 36 percent in 2005 to 65 percent in 2014.

Malaria treatment

Once diagnosed, artemisinin-based combination therapies (ACTs) are the mainstay of most treatments for malaria and should be administered within 24 hours of examination.

Severe malaria should be treated with injectable artesunate and followed by a complete course of an ACT as soon as the patient can take oral medicines.

By the end of 2013, ACTs had been adopted as a first-line treatment policy in 79 countries. In the same year, 337 million ACT treatment courses were delivered to endemic countries.

The WHO says access to ACTs among children in Africa remains poor but is improving. Based on data from household surveys and local medical centers, access rose from less than 1 percent in 2005 to 16 percent last year.