Although our attentions are currently focused on the Zika virus (and to a lesser extent, Dengue and Chikungunya) when it comes to imported vector borne diseases, there are plenty of others to worry about (see Yellow Fever In Angola & The Risk Of International Spread - ECDC).
Despite significant progress over the past 15 years in reducing its impact, Malaria continues to exact a heavy toll on global health. The World Malaria Report 2015 describes some of this progress:
The number of malaria cases globally fell from an estimated 262 million in 2000 (range: 205–316 million), to 214 million in 2015 (range: 149–303 million), a decline of 18%. Most cases in 2015 are estimated to have occurred in the WHO African Region (88%), followed by the WHO South-East Asia Region (10%) and the WHO Eastern Mediterranean Region (2%).
Malaria in the Americas is fairly rare, and in the Caribbean, only on the island of Hispaniola (Haiti/Dominican Republic) is Malaria still endemic. The vectors for Malaria - the Anopheles mosquito - remain, however.
And so there is always a concern that Malaria could be reintroduced to areas where it had previously been eradicated.
In 2010, in Florida: Locally Acquired Malaria Case Suspected, we looked at a rare case in a resident of Jacksonville with no history of international travel. In 1996 (2 cases) and again in 2003 (8 cases) of locally acquired P. vivax malaria were detected in Palm Beach County (see Multifocal Autochthonous Transmission of Malaria --- Florida, 2003).
Endemism in Florida has been avoided, primarily due to concerted mosquito control efforts, the annual winter semi-supression of mosquitoes, and a little bit of luck.
But each year scores (possibly hundreds) of international travels arrive carrying one of the four Malaria parasites (P. vivax, P. falciparum, P. malariae and P. ovale). The most recent Florida Arbovirus Surveillance report states:
International Travel-Associated Malaria Cases: Six cases of malaria with onset in 2016 have been reported. Countries of origin were: Angola, Cameroon, Kenya, Sudan, Uganda, and Venezuela. Counties reporting cases were: Broward (2), Flagler, Hillsborough, Orange, and Sarasota Counties. One case was reported in a non-Florida resident.
As worrisome as these cases are in Florida, concerns run even higher in Puerto Rico, which has a year-round tropical climate, abundant mosquito vectors, and a far less successful history of controlling mosquito borne diseases.
In 2010 Puerto Rico saw its worst Dengue epidemic since the 1990s which infected more than 21,000 people, killing 31 (see MMWR: Dengue Epidemic In Puerto Rico). In 2013 they saw another, albeit smaller, epidemic (see Puerto Rico: Dengue Levels Continue Above Epidemic Level).
In 2014 Chikungunya transmission reached epidemic proportions in Puerto Rico, and in recent months we've seen the arrival and spread of the Zika virus there as well.
Which makes repeated introductions of Malaria to Puerto Rico a serious public health concern, and brings us to an MMWR report on 7 imported cases last summer from the island of Hispaniola.
Notes from the Field: Imported Cases of Malaria — Puerto Rico, July–October 2015
Weekly / April 1, 2016 / 65(12);326–327On 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 mosquito-borne 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 ≥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 (http://www.cdc.gov/malaria/travelers/index.html). 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.