LONDON (Thomson Reuters Foundation) - Malaria can be eliminated soon, but only with much more investment, both to get rid of the disease and to keep it at bay, a former senior official of the World Health Organization (WHO) said.

Last week, Europe became the first region to be declared free of malaria after reporting no indigenous cases in 2015 in 53 countries which include Central Asia, Israel and Turkey.

The number of deaths from malaria has dropped by 60 percent since 2000, and the number of new cases by 37 percent.

Still, nearly half the world's population is at risk of the disease, and there were 214 million cases and 438,000 deaths reported last year, the vast majority in sub-Saharan Africa.

"It's very crucial that the world understands that ... malaria can be got rid of. That we're not condemned to live with such a dreadful disease - which is preventable and treatable - beyond our generation," Winnie Mpanju-Shumbusho said in an interview.

"I'm an optimist and I'm hoping to see that in my lifetime," she said.

Mpanju-Shumbusho retired in December as assistant director-general for HIV/AIDS, tuberculosis, malaria and neglected tropical diseases at the World Health Organization (WHO).

"History will judge us very harshly if we cannot use the knowledge we have, the tools we have and the resources we can mobilize together, to get rid of malaria once and for all," she told the Thomson Reuters Foundation.

Getting the job done requires political will, massive sustained investment in malaria control, communities that are engaged in the fight, and collaboration across sectors, she said.

Swaziland, Namibia, South Africa and Botswana are some of the countries on track for cutting the number of cases by at least 75 percent since 2000.

It is essential that efforts continue to the finishing line and beyond, Mpanju-Shumbusho said.

"For me that's the danger. Complacency can easily set in whenever you attack a disease to a certain level, people ... say we've calmed it down, it's no longer an issue."

If efforts to eliminate malaria relax near the end and it re-emerges, it could be very serious because people will no longer have any immunity to the disease, Mpanju-Shumbusho said.

"It's like a spring - when you let go, the rebound effect can be even worse than where you were in the beginning," she said.

Global spending on malaria is currently $2.7 billion a year. To achieve an internationally agreed target of a 90 percent cut in malaria cases by 2030, spending will need to rise to $8.7 billion a year by 2030, according to WHO.

A main channel of money for the fight is the Global Fund to Fight AIDS, Tuberculosis and Malaria, which receives funding from the Bill and Melinda Gates Foundation.

NIGERIA AIMS TO SLASH MALARIA

It is easier to reduce the malaria burden from a very high level to 20 percent, than from 20 percent to zero, said Kolawole Maxwell, country director for the non-profit Malaria Consortium in Nigeria.

"When you're moving from 20 to zero there's also a challenge of losing donors ... We need to recognize that if we don't move from 20 to zero all the investments of moving from 80 to 20 are likely to be lost.

"So we all need to keep the foot on the pedal," Maxwell said.

Nigeria accounted for a quarter of the world's malaria cases and 30 percent of its deaths in 2013.

The country plans to reduce the incidence of the disease to less than 10 percent of the population by 2020, Maxwell said. Some states have already achieved that, while others are nearer 40 percent, he said.

The country's rural poor are now the most likely to contract the disease because they do not use bednets - although they do own them, he said.

Maxwell said he himself used to be a "good customer of malaria" until he was convinced by the science to use a bednet. Since then, he has not had the disease.

In states where the incidence is nearer 10 percent of the population, greater surveillance is needed to reduce it further. The key is to find and treat people who do not yet have any symptoms but are carrying the parasite that causes malaria, he said.

Authorities in those states also need to prepare for emergencies, Maxwell said.

Adults living in areas where malaria is widespread develop some immunity to the disease, but if there is an outbreak in areas of low immunity the parasite is much more likely to kill.

Young children across the country have no immunity and can die unless they receive treatment within 24 hours.

"If I spent 5 minutes talking to you, it means one child has died in Nigeria within that period," Maxwell said.

"It doesn't have to be."

Mpanju-Shumbusho and Maxwell were in London this week for an event organized by UK Malaria Advocates, a network of organizations fighting malaria.

(Reporting by Alex Whiting, editing by Tim Pearce.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit http://news.trust.org)