The global dengue epidemic and the resurgence of Zika loom over Easter travel

Workers participate in a fumigation day in areas prone to the proliferation of dengue-transmitting mosquitoes in Acapulco (Mexico).David Guzmán (EFE)

Half a century ago, dengue was a public health problem in just half a dozen remote tropical areas of the planet.

The Spaniards who visited them were few and, if they contracted the disease, the risk of infecting other people upon their return was zero.

The situation, however, has taken a turn in recent times.

The virus that causes the disease has spread to become endemic in more than 100 countries.

Every year, hundreds of thousands of Spaniards spend their holidays there, as will happen this upcoming Holy Week.

And the presence of the tiger mosquito in much of Spain, where it was first established in 2004 and which is capable of transmitting the virus, means that indigenous outbreaks caused by people who become infected are now a reality.

“In a world undergoing a process of global transformation, the ways of traveling will also change forever,” says Manuel Linares Rufo, president of the iO Foundation, specialized in tropical and travel medicine.

Taking care of the health of oneself and others will be essential: “A simple example, but one that illustrates the magnitude of the changes that are coming, will be what to do when you return.

It was a time when you could relax and unwind.

But now, if you have traveled to one of the many destinations with dengue, you should remain alert for a week.

Don't let the tiger mosquito bite you, because this could be the origin of a local outbreak in your neighborhood or town."

The arrival of infected people to Spaniards allows the evolution of the disease to be followed in a kind of observatory.

In September 2022, they detected an increase in the incidence of dengue in tropical areas after the pandemic that was especially virulent in Cuba.

Last year, the impact of this disease had acquired epidemic magnitudes in most warm areas of the globe.

“The incidence continues to skyrocket.

“Across the world in general, but in the Americas in particular,”

says Marta Díaz, head of the Imported Pathology and International Health Unit of the Carlos III Hospital (Madrid), in reference to tourist destinations in tropical areas and some with temperate climates in summer.

“We have had a very busy month of January and February, when it is normal for the number of cases that reach us to decrease.

It has been something very striking,” highlights this expert.

An operator fumigates the playground of a school in Brazil. Associated Press/LaPresse (APN)

A recent publication by the European Center for Disease Control and Prevention (ECDC), with data for the quarter between November 2023 and January 2024, warns of the high incidences registered in much of the globe, with “more than half a million new cases and more than a hundred reported deaths.”

America is the hardest hit continent, with more than 550,000 cases in January, triple that of the same month in 2023. All countries from Mexico to Argentina, except Chile and Uruguay - Venezuela and Cuba have not published data - present incidences greater than 100 cases per 100,000 inhabitants.

The magnitude of the outbreak has led Brazil to be the first country in the world to launch a vaccination campaign against the disease in public health.

The vaccine used is the one marketed under the name Qdenga, from the Japanese pharmaceutical company Takeda and approved in Europe since the end of 2022. “It is a vaccine that is administered in two doses separated by three months, although the first puncture already offers good protection starting from 14 days and for several months,” Natividad Tolosa, from the Spanish Association of Vaccinology (AEV), explained last Tuesday at an informative event on the disease held in Barcelona by the National Association of Health Informants (ANIS). ).

According to available data, the vaccine has an effectiveness slightly higher than 61%, although this percentage is much higher against serotypes 1 and 2 of the disease and lower for serotypes 3 and 4 (all four are currently circulating in American countries. ).

This vaccine has only just begun to be used in Spain and is indicated for travelers traveling to areas with a high incidence and who may suffer serious symptoms due to their clinical history.

Dengue infection, which can occur asymptomatically, manifests with flu-like symptoms and a rash.

About one in 20 cases, however, will develop a severe or hemorrhagic condition, which is associated with high mortality.

The virus is spread by mosquito bites and not from person to person.

In tropical countries, the species responsible for infections is

Aedes aegypti,

which is a more efficient vector than the tiger mosquito (

Aedes albopictus).

After dengue, chikungunya is the second disease in number of imported cases detected in Spain.

This disease is transmitted by the mosquitoes themselves and is characterized by intense pain in the joints.

In fact, his name means “bent man” in a Tanzanian language.

In the last year, the virus has been circulating in some American countries, such as Brazil and Paraguay, especially, although also in others in Africa (Mali and Burkina Faso are the most affected) and in Asia, such as India.

According to the ECDC, in the first month of 2024 there have been about 10,000 cases in the world and no deaths from this disease.

The chikungunya incidence does not present major changes compared to 2023.

The great change in trend is being carried out in recent times by a third virus transmitted by the same mosquitoes, Zika, whose circulation was practically anecdotal since the great epidemic that it caused in America in 2015 and 2016. “The number of cases that are being registered is still small in absolute terms, but the trend is clearly upward.

In countries like Thailand, an important destination for Spanish travelers, it has grown by close to 300%,” warns Marta Díaz.

Nerea Irigoyen is a researcher specializing in the Zika virus and group leader in the Department of Pathology at the University of Cambridge.

“The incidences have been very low after the great epidemic eight years ago, which is explained by the natural immunity developed by the population.

But it declines over time and studies show that it is doing so faster than expected, so it cannot be ruled out that we are on the verge of an increase in cases,” she says.

Zika is considered a virus that generally causes milder symptoms than dengue and chikungunya, although similar.

“But it is a significant risk during pregnancy, because it can cause microcephaly and other damage to the brain of the unborn baby.

Furthermore, it is a virus that is transmitted sexually,” adds Irigoyen.

By sharing a transmission route, mosquito bites, the three viruses—dengue, chikungunya and Zika—are prevented in the same way: use of repellents, mosquito nets, wearing long clothes and, preferably, sleeping in places with air conditioning (which Avoid doing it with the windows open to facilitate mosquito access).

Measles is the other infectious disease whose incidence is growing in much of the world, also in Europe.

"It has nothing to do with tropical diseases, but the increase in cases that we are seeing reminds us of the need to maintain high vaccination coverage, above 95%, to avoid outbreaks such as those that have already begun to be initiated by cases imported,” concludes Linares Rufo.