“It is highly unlikely that there will be a reintroduction of malaria in Portugal” so long as there is a public health service and appropriate surveillance measures, said Miguel Prudêncio, who leads a research and development team working on a vaccine at the country’s Institute of Molecular Medicine.

Although climate change can “foster an increase in mosquitoes”, the likelihood of this leading to the return of malaria to Portugal is not great because the country’s health system ensures the “containment of parasite reservoirs” that cause the disease.

According to Prudêncio, only in a situation in which the surveillance and health systems break down would the scenario be different – and he does not see this as realistic.

“I think climate change has devastating potential and notably for Portugal, which has a large coastal area, but not by increasing malaria transmission,” he said in comments to Lusa.

Malaria, a disease caused by a parasite that is transmitted by the bites of the Anopheles mosquito, requires three vectors to be transmitted: the parasite, the mosquito and the human being.

The mosquito does exist in Portugal but the parasite, to survive, requires conditions that favour its development, which does not happen if infected people are treated, so interrupting its reproductive cycle.

“In a functioning health system, a person who has the parasite will be detected, diagnosed and treated, and the area where it has circulated will be monitored to detect possible cases of malaria,” stressed the scientist. “Therefore, the parasite reservoir is destroyed before it can be expanded.”.

To illustrate his position, Prudêncio cited two episodes – in 1974 and 1976 – that could have facilitated the reintroduction of malaria in Portugal, but which did not.

He recalled the arrival in those years of thousands of people from Portugal’s former colonies, many from regions where malaria was endemic, who were potentially infected with the parasite. Yet even though Portugal’s health system was then “much weaker”, malaria did not re-establish itself.

More recently, Greece and Italy have suffered outbreaks of locally transmitted malaria in regions where there was a large concentration of migrants, but these were immediately stamped out.

“There would have to be an absolute breakdown of the health system for it not be contained,” Prudência said.

The last case of malaria contracted in Portugal was recorded in 1959. The disease has been eradicated in the country thanks to insecticide sprays, anti-malarial drugs and public awareness campaigns, but remains endemic in large parts of Africa, Asia and Latin America.

It is estimated that about 200 million people are exposed to the disease and annually, about 500,000 die, especially children under the age of five.

In addition to the development of a vaccine, part of the investment in the fight against the disease has been directed towards preventive measures, such as mosquito nets, which has helped control malaria in some African countries, such as Sao Tome and Principe and Cabo Verde. However, it is difficult to implement this right across the continent.

“Doing this on a large scale is very complicated from the economic, logistical point of view” and even because of “cultural specificities” that make eradicating malaria with insecticides and nets impracticable, Prudêncio argued. The distribution of this equipment is hindered by poor accessibility in many regions, and the nets are not always used as they should be, with some even ending up being used for fishing.

It is, Prudêncio notes, easier to succeed in small areas that are clearly physically delimited, such as islands.