GENEVA (Reuters) - Malaria is spreading rapidly in crisis-hit Venezuela, with more than an estimated 406,000 cases in 2017, up roughly 69 percent from a year before, the largest increase worldwide, the World Health Organization (WHO) said on Tuesday.

Venezuelan migrants fleeing the economic and social crisis are carrying the mosquito-borne disease into Brazil and other parts of Latin America, the U.N. agency said, urging authorities to provide free screening and treatment regardless of their legal status to avoid further spread.

“In the Americas, it’s not just Venezuela. We’re actually reporting increases in a number of other countries. Venezuela, yes this is a significant concern, malaria is increasing and it’s increasing in a very worrying way,” Pedro Alonso, director of WHO’s global malaria program, told a news briefing.

Venezuela is slipping into hyperinflation with shortages of food and medicines during a fifth year of recession that President Nicolas Maduro’s government blames on Western hostility and falling oil prices.

Venezuelan officials reported 240,613 malaria cases in 2016, many in the gold-mining state of Bolivar bordering Guyana, with an estimated 280 deaths, according to the WHO.

The 2017 estimate has leapt to 406,000 cases - five times higher than in 2013.

“What we are now seeing is a massive increase, probably reaching close to half a million cases per year. These are the largest increases reported anywhere in the world,” Alonso said.

A lack of resources and ineffective anti-malaria campaigns were to blame, he said. WHO and the Pan-American Health Organization (PAHO) are working with Venezuelan authorities to address the situation, he added.

“We are seeing indeed because of population movement, cases among Venezuelan migrants appearing in other countries - Brazil certainly. But also in Colombia, in Ecuador and in a number of other places,” Alonso said.

“What this calls for is renewed effort by the countries surrounding Venezuela to ensure adequate diagnosis and treatment free for whoever shows up at medical services,” he said.

The global campaign against the life-threatening disease has stalled for the first time in a decade, with a reversal of gains made in some countries, the WHO said last November.

Malaria infected around 216 million people in 91 countries in 2016, killing 445,000, with 90 percent of cases and fatalities in sub-Saharan Africa, it said.