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Notes From Puerto Rico: Quakes Increase Risk for Mosquito-Borne Disease Outbreak

Puerto Rico earthquake damage January 2020

A series of earthquakes in Puerto Rico in early January has severely damaged structures in areas such as the town of Guanica. A ripple effect of the damage to homes is an increase in exposure to mosquito-borne disease for residents forced to dwell outdoors during the recovery. (Photo by Jose R. Madera, Puerto Rico Science Technology and Research Trust)

By Grayson Brown, Ph.D.

Puerto Rico has experienced a swarm of earthquakes and tremors over the past two weeks. The biggest were a 5.8 magnitude earthquake on January 6, a 6.5 magnitude earthquake on January 7, and a 5.9 magnitude earthquake on January 11. All of these, along with hundreds of lesser tremors, have occurred in the same area in south central Puerto Rico. The affected region, from Guanica to Ponce, is mostly rural and agricultural and populated by small and isolated towns and villages.

Grayson Brown, Ph.D.

Grayson Brown, Ph.D.

Nearly all structures in this region have suffered significant damage. Many of those that remain at least partially standing are unsafe. Almost all people in the area are afraid to spend any time indoors under any roof. Many have fled the area to temporarily stay with friends and family, particularly in the San Juan and Carolina areas to the northeast.

The Problem

Most people, however, have stayed at or near their homes and can, for the most part, get into their houses to retrieve water, clothing, food, hardware, and so forth. However, almost all of them cook, eat, and sleep outdoors. There are shelters, but they are all open-air (because people are afraid to sleep under a roof), and, in any case, people are reluctant to leave their homes for fear that their possessions will be stolen. Instead, most families stay in their front yard guarding their possessions round the clock, taking turns sleeping during the day. Consequently, while there are many people sleeping outdoors, there are not tent-city style refugee camps.

Thus, thousands of Puerto Ricans are exposed to mosquito bites. The Puerto Rico Vector Control Unit (PRVCU) has monitored the mosquitoes in this area and found the vast majority to be Aedes aegypti, Aedes taeniorhynchus, and Culex quinquefasciatus. In Puerto Rico, the latter two species are primarily nuisance species, but Ae. aegypti is a serious disease vector. Unfortunately, recent heavy rains have increased the populations of these species to high levels.

To make matters worse, Puerto Rico appears to be in the early stages of a dengue outbreak (this has been a record year for dengue in the Caribbean), with cases increasing rapidly in the major metropolitan areas of San Juan and Carolina. Mosquito-borne disease outbreaks in Puerto Rico typically begin in those cities and then spread throughout the rest of the island. We worry that some of the people who have fled to these areas will take dengue back with them when they return.

Relief Needs

Many relief agencies are working in Puerto Rico right now, but only the PRVCU is targeting vector-borne disease mitigation. The PRVCU has been working with the local town and village leadership throughout the area and is distributing repellent and flyers on how people can protect themselves from mosquito bites. We have distributed over 6,000 units of repellents to date, mostly by going house-to-house. This morning, we had about 6,000 still in inventory and received a shipment of 4,000 more. We have 5,000 more on the way, and our supplier has another 6,000 in reserve. We’re in good shape with respect to repellent.

However, we have run out of bed nets and have been making do with makeshift nets. We don’t necessarily need insecticide-treated nets (ITNs) but will happily use them if they are registered for use in Puerto Rico. Some have been offered to us that do not have that registration, and we are looking into getting emergency registration for ITNs here. However, knowing the relevant offices within the PR government, I’m not hopeful in accomplishing that in time.

We estimate that we need 4,000 to 5,000 nets, mostly full size, but a few hundred crib size would be beneficial as well. We can buy them but mostly need to find a source that can get them here as fast as possible.

Editor’s Note: The Entomological Society of America is coordinating through fellow members of the Vector-Borne Disease Network to help Puerto Rico Vector Control Unit respond to this crisis and receive the assistance it needs. To help support disaster relief in Puerto Rico, consider donating to the Hispanic Federation’s Unidos program. To support global response in regions where malaria is carried by mosquitoes, consider donating to Nothing But Nets.

Grayson Brown, Ph.D., is executive director of the Puerto Rico Vector Control Unit and a past president of the Entomological Society of America. Email:

1 Comment »

  1. Hola mis más grandes brazos fraternales a esa hermana nac´ión, lo que necesiten de mi pueden contar conmigo.

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