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Imported cases of malaria--Puerto Rico, July-October 2015.

On July 16 2015, the Puerto Rico Department of Health (PRDH) was notified of a case of malaria, diagnosed by a hospital parasitology laboratory in a student who had traveled to Punta Cana, Dominican Republic, during late June for a school-organized graduation trip. Malaria is a mosquitoborne parasitic infection, characterized by fever, shaking chills, headaches, muscle pains, nausea, general malaise, and vomiting (1). Malaria can be clinically difficult to distinguish from other acute febrile illnesses, and a definitive diagnosis requires demonstration of malaria parasites using microscopy or molecular diagnostic tests. The student's initial diagnosis on July 10 was suspected dengue virus infection. Puerto Rico eliminated local malaria transmission during the mid-1950s (2); however, reintroduction remains a risk because of the presence of a competent vector (Anopheles albimanus) and ease of travel to areas where the disease is endemic, including Hispaniola, the island shared by the Dominican Republic and Haiti, and the only island in the Caribbean with endemic malaria (3). During 2014, the Dominican Republic reported 496 confirmed malaria cases and four associated deaths; Haiti reported 17,662 confirmed cases and nine deaths (4). During 2000-2014, Puerto Rico reported a total of 35 imported malaria cases (range = 0-7 per year); three cases were imported from Hispaniola. During June-August 2015, eight confirmed malaria cases among travelers to the Dominican Republic were reported to CDC's National Malaria Surveillance System (CDC, unpublished data, 2015).

After the student's diagnosis of malaria, an epidemiologic investigation was undertaken by PRDH to identify additional cases among the 90 school trip participants. A suspected malaria case was defined as the occurrence of any symptoms consistent with malaria (i.e., fever, shaking chills, headaches, muscle pains, nausea, general malaise, and vomiting) occurring in a school trip participant [greater than or equal to]9 days after travel to the Dominican Republic. During interviews with participants, investigators learned that a second Puerto Rico school group (n = 44) had visited the same resort during the same time; thus, the investigation was expanded from 90 to 134 participants. To help find other suspected cases, PRDH released a health alert notice on July 17 to all health care providers in Puerto Rico; public health counterparts in the Dominican Republic were also informed.

Seven suspected cases were identified among school trip participants, and during July 16-August 21, health care providers in Puerto Rico sent 102 additional patient specimens to PRDH for evaluation by smear microscopy. Among the 109 total patient samples, 27 (25%) met the suspected case definition and were sent to CDC for testing by photo-induced electron transfer fluorogenic real-time polymerase chain reaction. Plasmodium falciparum malaria was diagnosed in five patients, including two from the first school group, two from the second school group, and one in an independent traveler from Puerto Rico (Table). Microsatellite loci evaluation indicated genetic similarity among isolates from the five patients as well as with previous malaria cases from Hispaniola. The five malaria patients were successfully treated. Two subsequent cases of P falciparum malaria among self-organized travelers from Puerto Rico to Punta Cana were reported during September and October 2015.

This cluster of imported malaria cases highlights the importance of malaria surveillance in areas where the disease is not endemic to detect imported cases. Travelers should be informed of risks before visiting locations where malaria is endemic and take recommended precautions, including avoiding exposure to mosquitoes, using mosquito repellent, and taking recommended chemoprophylaxis ( Physician awareness of malaria symptoms and patient travel histories is critical for timely diagnosis and effective patient care. Febrile travelers from areas where malaria is endemic should be promptly evaluated by thin and thick smear microscopy for malaria infection, and public and private health institutions should maintain the ability to test for and report confirmed cases of malaria to public health authorities.


Bernard Christiansen, Grupo HIMA San Pablo; Puerto Rico Department of Health regional epidemiologists and Public Health Laboratory personnel.


(1.) CDC. Malaria. Atlanta, GA: US Department of Health and Human Services, CDC; 2015.

(2.) Miranda Franco R, Casta Velez A. La erradicacion de la malaria en Puerto Rico.[Spanish]. Rev Panam Salud Publica 1997; 2:146-50. http://dx.doi. org/10.1590/S1020-49891997000800015

(3.) Herrera S, Ochoa-Orozco SA, Gonzalez IJ, Peinado L, Quinones ML, Arevalo-Herrera M. Prospects for malaria elimination in Mesoamerica and Hispaniola. PLoS Negl Trop Dis 2015; 9:e0003700. http://dx.doi. org/10.1371/journal.pntd.0003700

(4.) World Health Organization. World Malaria Report, 2015. Geneva, Switzerland: World Health Organization; 2015. bitstream/10665/200018/1/9789241565158_eng.pdf?ua=1

Emilio Dirlikov, PhD [1, 2]; Carmen Rodriguez, Laura Castro Martinez, MPH [2]; Juan B. Mendez MPH [2]; Anibal Cruz Sanchez, MPH [2]; Jesus Hernandez Burgos, MPH [2]; Zobeida Santiago, MPH2; Rosa Ivette Cuevas-Ruis [2]; Sheila Adorno Camacho [2]; Enid Roman Mercado [2]; Jessica Kyle Ryff, MPH [2]; Carolina Luna Pinto, MPH [5]; Paul M. Arguin, MD [6]; Stella M. Chenet, PhD [6]; Luciana Silva-Flannery, PhD [6]; Dragan Ljolje [6]; Julio Cadiz Velazquez, MD [2]; Dana Thomas, MD [2, 4]; Brenda Rivera Garcia, DVM [2]

[1] Epidemic Intelligence Service, Division of Scientific Education and Professional Development, CDC; [2] Puerto Rico Department of Health; [3] Cook County Department of Public Health, Illinois; [4] Office of Public Health Preparedness and Response, CDC; [5] CDC San Juan Quarantine Station; [6] Malaria Branch, Division of Parasitic Diseases and Malaria, CDC.

Corresponding author: Emilio Dirlikov,, 734-635-0082.
TABLE. Characteristics of patients with confirmed Plasmodium
falciparum malaria who had traveled to the Dominican Republic--Puerto
Rico, June-July, 2015

Patient     Age                 Travel dates to
no.        (yrs)      Sex     Dominican Republic     Travel type *

1            18      Male       June 22-June 26      School trip 1
2            17     Female      June 22-June 26      School trip 1
3            18      Male       June 22-June 26      School trip 2
4            47      Male       June 22-June 27     Self-organized
5            17     Female      June 22-June 26      School trip 2

Patient       Date of       Date first sought    Date of hospital
no.        symptom onset       medical care          admission

1             July 10            July 14              July 15
2              July 9            July 13              July 15
3             July 10            July 14              July 14
4              July 8            July 13              July 13
5             July 11            July 13              July 14

Patient    Initial diagnosis    Date reported
no.            suspected           to PRDH

1                Dengue            July 16
2                Dengue            July 17
3            Viral syndrome        July 20
4                Dengue            July 21
5            Viral illness         July 20

Abbreviation: PRDH = Puerto Rico Department of Health.

* Epidemiologic investigation revealed cases resulting from two
overlapping school trips to the same hotel in the Dominican Republic.
An independent traveler staying at a different hotel in the region was
also identified.
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Article Details
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Title Annotation:Notes from the Field
Author:Dirlikov, Emilio; Rodriguez, Carmen; Morales, Shirley; Martinez, Laura Castro; Mendez, Juan B.; Sanc
Publication:Morbidity and Mortality Weekly Report
Geographic Code:5DOMN
Date:Apr 1, 2016
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