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Mosquito-borne arboviruses are an important cause of morbidity and mortality in the Caribbean. In Puerto Rico, chikungunya, dengue, and Zika viruses have each caused large outbreaks during 2010–2022. To date, the majority of control measures to prevent these diseases focus on mosquito control and many require community participation. In 2018, the U.S. Centers for Disease Control and Prevention launched the COPA project, a community-based cohort study in Ponce, Puerto Rico, to measure the impact of novel vector control interventions in reducing arboviral infections. Randomly selected households from 38 designated cluster areas were offered participation, and baseline data were collected from 2,353 households between May 2018 and May 2019. Household-level responses were provided by one representative per home. Cross-sectional analyses of baseline data were conducted to estimate 1) the association between arboviral risk perception and annual household expenditure on mosquito control, and 2) the association between arboviral risk perception and engagement in ≥3 household-level risk reduction behaviors. In this study, 27% of household representatives believed their household was at high risk of arboviruses and 36% of households engaged in at least three of the six household-level preventive behaviors. Households where the representative perceived their household at high risk spent an average of $35.9 (95% confidence interval: $23.7, $48.1) more annually on mosquito bite prevention compared to households where the representative perceived no risk. The probability of engaging in ≥3 household-level mosquito-preventive behaviors was 10.2 percentage points greater (7.2, 13.0) in households where the representatives perceived high risk compared to those in which the representatives perceived no risk. Paired with other research, these results support investment in community-based participatory approaches to mosquito control and providing accessible information for communities to accurately interpret their risk.Author SummaryMosquito-borne disease is an important cause of illness and death in the Caribbean, including Puerto Rico. Most tactics to prevent these diseases rely on stopping mosquito bites, either by reducing the mosquito population or creating barriers between mosquitos and humans. These methods vary in the degree of community involvement required. This study used data collected from 2,353 households in Ponce, Puerto Rico from May 2018 to May 2019 to understand how household perception of risk of contracting these diseases related to 1) the amount of money households spent annually to prevent mosquito bites, and 2) the number of activities their household engaged in to prevent mosquito bites. We found that 27% of households perceived themselves at high risk of contracting these diseases, and 36% of households engaged in at least three activities to reduce their risk. On average, households that perceived themselves at high risk spent more money on mosquito bite prevention and engaged in more activities to prevent mosquito bites, compared to households that perceived no risk. Paired with other research in this area, these results support investment in community-based approaches to mosquito control and ensuring that communities have accessible information to understand their risk of mosquito-borne disease.

As of January 20, 2022, > 247,000 confirmed COVID-19 cases and 3,600 deaths were reported in Puerto Rico (PR). We interviewed participants aged ≥ 14 years in the Communities Organized to Prevent Arboviruses (COPA) study, a community-based cohort in PR, about COVID-19 vaccine intention from November 12, 2020, to June 25, 2021. We used univariate and adjusted analyses to identify participant characteristics associated with vaccine intention. Among 1,542 respondents, the median age was 37 years (interquartile range 23–45) and 914 (59%) were female. Most participants (83%) reported a willingness to receive a COVID-19 vaccine. The most common reason for vaccine hesitancy was concern about the safety or side effects (64%). Willingness to receive the COVID-19 vaccine was associated with a later interview date, higher household income, previous COVID-19 diagnosis among household members, COVID-19 risk perception, influenza vaccine uptake, dengue vaccine intention, and general positive perceptions of vaccines. While parents with minors (< 21 years old) were less likely to report vaccine intention for themselves than participants without minor children, we observed similar characteristics associated with parents’ willingness to vaccinate their children. Overall, COVID-19 vaccine intention was high among COPA participants. It is important that public health messaging in PR addresses COVID-19 vaccine safety and possible side effects.

Dengue was first reported in Puerto Rico in 1899 and sporadically thereafter. Following outbreaks in 1963 and 1969, the Centers for Disease Control and Prevention has worked closely with the Puerto Rico Department of Health to monitor and reduce the public health burden of dengue. During that time, evolving epidemiologic scenarios have provided opportunities to establish, improve, and expand disease surveillance and interventional research projects. These initiatives have enriched the tools available to the global public health community to understand and combat dengue, including diagnostic tests, methods for disease and vector surveillance, and vector control techniques. Our review serves as a guide to organizations seeking to establish dengue surveillance and research programs by highlighting accomplishments, challenges, and lessons learned during more than a century of dengue surveillance and research conducted in Puerto Rico.

The U.S. territory of American Samoa has experienced recent outbreaks of illnesses caused by viruses transmitted by Aedes species mosquitoes, including dengue, chikungunya, and Zika virus. In November 2016, a traveler from the Solomon Islands tested positive for infection with dengue virus type 2 (DENV-2). Additional dengue cases were identified in the subsequent weeks through passive and active surveillance. Suspected dengue cases were tested locally with a dengue rapid diagnostic test (RDT) for DENV nonstructural protein 1 (NS1). Specimens from RDT-positive cases and patients meeting the dengue case definition were tested by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) at Hawaii State Laboratories. During November 2016-October 2018, a total of 3,240 patients were tested for evidence of DENV infection (118 by RDT-NS1 alone, 1,089 by real-time RT-PCR alone, and 2,033 by both methods), 1,081 (33.4%) of whom tested positive for dengue (19.5 per 1,000 population). All 941 real-time RT-PCR-positive specimens were positive for DENV-2. The monthly number of laboratory-confirmed cases peaked at 120 during December 2017. Among laboratory-confirmed dengue cases, 380 (35.2%) patients were hospitalized; one patient, who was transferred to American Samoa for care late in his illness, died. The public health response to this outbreak included disposal of solid waste to remove mosquito breeding sites, indoor residual spraying of pesticides in schools, reinforcement of dengue patient management education, and public education on mosquito avoidance and seeking medical care for symptoms of dengue.

The exotic arboviruses chikungunya (CHIKV) and Zika (ZIKV) recently caused large outbreaks and continue to circulate in Puerto Rico, prompting entomological investigations at 9 locations with confirmed CHIKV- or ZIKV-infected human cases. Adult mosquitoes were collected using the Centers for Disease Control and Prevention autocidal gravid ovitraps over a 14-day period at each site. Mean female Aedes aegypti captured per trap-week ranged from 13.47 per trap-week to 1.27 per trap-week. Arbovirus-positive pools were detected at 7 of the 9 sampling sites. We investigated vertical transmission by collecting Ae. aegypti eggs in a single location where ZIKV was found in adult mosquitoes. We discuss the relationship between vector density and infection rates and its implications for determining mosquito density thresholds of novel invasive arboviruses such as CHIKV and ZIKV.

Background The burden of leptospirosis in Puerto Rico remains unclear due to underreporting. Methods A cross-sectional survey and rodent trapping was performed in a community within San Juan, Puerto Rico to determine the seroprevalence and risk factors for Leptospira infection. The microscopic agglutination test was used to detect anti-Leptospira antibodies as a marker of previous infection. We evaluated Leptospira carriage by quantitative polymerase chain reaction among rodents trapped at the community site. Results Of 202 study participants, 55 (27.2%) had Leptospira agglutinating antibodies. Among the 55 seropositive individuals, antibodies were directed most frequently against serogroups Icterohaemorrhagiae (22.0%) and Autumnalis (10.6%). Of 18 captured rodents, 11 (61.1%) carried pathogenic Leptospira (Leptospira borgpetersenii, 7 and Leptospira interrogans, 2). Four participants showed their highest titer against an isolate obtained from a rodent (serogroup Ballum). Increasing household distance to the canal that runs through the community was associated with decreased risk of infection (odds ratio = 0.934 per 10-meter increase; 95% confidence interval, .952–.992). Conclusions There are high levels of Leptospira exposure in an urban setting in Puerto Rico, for which rodents may be an important reservoir for transmission. Our findings indicate that prevention should focus on mitigating risk posed by infrastructure deficiencies such as the canal.

After chikungunya virus (CHIKV) transmission was detected in Puerto Rico in May 2014, multiple surveillance systems were used to describe epidemiologic trends and CHIKV-associated disease. Of 28 327 cases reported via passive surveillance, 6472 were tested for evidence of CHIKV infection, and results for 4399 (68%) were positive. Of 250 participants in household cluster investigations, 70 (28%) had evidence of recent CHIKV infection. Enhanced surveillance for chikungunya at 2 hospitals identified 1566 patients who tested positive for CHIKV, of whom 10.9% were hospitalized. Enhanced surveillance for fatal cases enabled identification of 31 cases in which CHIKV was detected in blood or tissue specimens. All surveillance systems detected a peak incidence of chikungunya in September 2014 and continued circulation in 2015. Concomitant surveillance for dengue demonstrated low incidence, which had decreased before CHIKV was introduced. Multifaceted chikungunya surveillance in Puerto Rico resolved gaps in traditional passive surveillance and enabled a holistic description of the spectrum of disease associated with CHIKV infection.

Deaths were rarely observed, but newborns and other vulnerable populations are at risk for severe complications., Chikungunya virus (CHIKV) caused large epidemics throughout the Caribbean in 2014. We conducted nucleic acid amplification testing (NAAT) for CHIKV RNA (n = 29,695) and serologic testing for IgG against CHIKV (n = 1,232) in archived blood donor samples collected during and after an epidemic in Puerto Rico in 2014. NAAT yields peaked in October with 2.1% of donations positive for CHIKV RNA. A total of 14% of NAAT-reactive donations posed a high risk for virus transmission by transfusion because of high virus RNA copy numbers (104–109 RNA copies/mL) and a lack of specific IgM and IgG responses. Testing of minipools of 16 donations would not have detected 62.5% of RNA-positive donations detectable by individual donor testing, including individual donations without IgM and IgG. Serosurveys before and after the epidemic demonstrated that nearly 25% of blood donors in Puerto Rico acquired CHIKV infections and seroconverted during the epidemic.

Zika virus is a flavivirus transmitted primarily by Aedes species mosquitoes, and symptoms of infection can include rash, fever, arthralgia, and conjunctivitis (1).* Zika virus infection during pregnancy is a cause of microcephaly and other severe brain defects (2). Infection has also been associated with Guillain-Barré syndrome (3). In December 2015, Puerto Rico became the first U.S. jurisdiction to report local transmission of Zika virus, with the index patient reporting symptom onset on November 23, 2015 (4). This report provides an update to the epidemiology of and public health response to ongoing Zika virus transmission in Puerto Rico. During November 1, 2015-April 14, 2016, a total of 6,157 specimens from suspected Zika virus-infected patients were evaluated by the Puerto Rico Department of Health (PRDH) and CDC Dengue Branch (which is located in San Juan, Puerto Rico), and 683 (11%) had laboratory evidence of current or recent Zika virus infection by one or more tests: reverse transcription-polymerase chain reaction (RT-PCR) or immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA). Zika virus-infected patients resided in 50 (64%) of 78 municipalities in Puerto Rico. Median age was 34 years (range = 35 days-89 years). The most frequently reported signs and symptoms were rash (74%), myalgia (68%), headache (63%), fever (63%), and arthralgia (63%). There were 65 (10%) symptomatic pregnant women who tested positive by RT-PCR or IgM ELISA. A total of 17 (2%) patients required hospitalization, including 5 (1%) patients with suspected Guillain-Barré syndrome. One (1%) patient died after developing severe thrombocytopenia. The public health response to the outbreak has included increased laboratory capacity to test for Zika virus infection (including blood donor screening), implementation of enhanced surveillance systems, and prevention activities focused on pregnant women. Vector control activities include indoor and outdoor residual spraying and reduction of mosquito breeding environments focused around pregnant women's homes. Residents of and travelers to Puerto Rico should continue to employ mosquito bite avoidance behaviors, take precautions to reduce the risk for sexual transmission (5), and seek medical care for any acute illness with rash or fever.

Zika virus, a mosquito-borne flavivirus, spread to the Region of the Americas (Americas) in mid-2015, and appears to be related to congenital microcephaly and Guillain-Barré syndrome (1,2). On February 1, 2016, the World Health Organization (WHO) declared the occurrence of microcephaly cases in association with Zika virus infection to be a Public Health Emergency of International Concern.* On December 31, 2015, Puerto Rico Department of Health (PRDH) reported the first locally acquired (index) case of Zika virus disease in a jurisdiction of the United States in a patient from southeastern Puerto Rico. During November 23, 2015-January 28, 2016, passive and enhanced surveillance for Zika virus disease identified 30 laboratory-confirmed cases. Most (93%) patients resided in eastern Puerto Rico or the San Juan metropolitan area. The most frequently reported signs and symptoms were rash (77%), myalgia (77%), arthralgia (73%), and fever (73%). Three (10%) patients were hospitalized. One case occurred in a patient hospitalized for Guillain-Barré syndrome, and one occurred in a pregnant woman. Because the most common mosquito vector of Zika virus, Aedes aegypti, is present throughout Puerto Rico, Zika virus is expected to continue to spread across the island. The public health response in Puerto Rico is being coordinated by PRDH with assistance from CDC. Clinicians in Puerto Rico should report all cases of microcephaly, Guillain-Barré syndrome, and suspected Zika virus disease to PRDH. Other adverse reproductive outcomes, including fetal demise associated with Zika virus infection, should be reported to PRDH. To avoid infection with Zika virus, residents of and visitors to Puerto Rico, particularly pregnant women, should strictly follow steps to avoid mosquito bites, including wearing pants and long-sleeved shirts, using permethrin-treated clothing and gear, using an Environmental Protection Agency (EPA)-registered insect repellent, and ensuring that windows and doors have intact screens.

On December 1, 2015, the Puerto Rico Department of Health (PRDH) was notified by a local hospital of a suspected human rabies case. The previous evening, a Puerto Rican man aged 54 years arrived at the emergency department with fever, difficulty swallowing, hand paresthesia, cough, and chest tightness. The next morning the patient left against medical advice but returned to the emergency department in the afternoon with worsening symptoms. The patient's wife reported that he had been bitten by a mongoose during the first week of October, but had not sought care for the bite. While being transferred to the intensive care unit, the patient went into cardiac arrest and died. On December 3, rabies was confirmed from specimens collected during autopsy. PRDH conducted an initial rapid risk assessment, and five family members were started on rabies postexposure prophylaxis (PEP).

IntroductionThe 2015-2017 Zika virus (ZIKV) epidemic in the Americas has driven efforts to strengthen surveillance systems and to develop interventions, testing, and travel recommendations. In the continental U.S. and Hawaii, where limited transmission has been observed, detecting local transmission is a key public health objective. We assessed the effectiveness of three general surveillance strategies for this situation: testing all pregnant women twice during pregnancy, testing blood donations, and testing symptomatic people who seek medical care in an emergency department (ED).MethodsWe developed a simulation model for each surveillance strategy and simulated different transmission scenarios with varying population sizes and infection rates. We then calculated the probability of detecting transmission, the number of tests needed, and the number of false positive test results.ResultsThe probability of detecting ZIKV transmission was highest for testing ED patients with Zika symptoms, followed by pregnant women and blood donors, in that order. The magnitude of the difference in probability of detection between strategies depended on the incidence of infection. Testing ED patients required fewer tests and resulted in fewer false positives than surveillance among pregnant women. The optimal strategy identified was to test ED patients with at least two Zika virus disease symptoms. This case definition resulted in a high probability of detection with relatively few tests and false positives.DiscussionIn the continental U.S. and Hawaii, where local ZIKV transmission is rare, optimizing the probability of detecting infections while minimizing resource usage is particularly important. Local surveillance strategies will be influenced by existing public health system infrastructure, but should also consider the effectiveness of different approaches. This analysis demonstrated differences across strategies and indicated that testing symptomatic ED patients is generally a more efficient strategy for detecting transmission than routine testing of pregnant women or blood donors.

Background. Melioidosis results from infection with Burkholderia pseudomallei and is associated with casefatality rates up to 40%. Early diagnosis and treatment with appropriate antimicrobials can improve survival rates. Fatal and nonfatal melioidosis cases were identified in Puerto Rico in 2010 and 2012, respectively, which prompted contact investigations to identify risk factors for infection and evaluate endemicity. Methods. Questionnaires were administered and serum specimens were collected from coworkers, neighborhood contacts within 250 m of both patients’ residences, and injection drug user (IDU) contacts of the 2012 patient. Serum specimens were tested for evidence of prior exposure to B. pseudomallei by indirect hemagglutination assay. Neighborhood seropositivity results guided soil sampling to isolate B. pseudomallei. Results. Serum specimens were collected from contacts of the 2010 (n = 51) and 2012 (n = 60) patients, respectively. No coworkers had detectable anti–B. pseudomallei antibody, whereas seropositive results among neighborhood contacts was 5% (n = 2) for the 2010 patient and 23% (n = 12) for the 2012 patient, as well as 2 of 3 IDU contacts for the 2012 case. Factors significantly associated with seropositivity were having skin wounds, sores, or ulcers (odds ratio [OR], 4.6; 95% confidence interval [CI], 1.2–17.8) and IDU (OR, 18.0; 95% CI, 1.6–194.0). Burkholderia pseudomallei was isolated from soil collected in the neighborhood of the 2012 patient. Conclusions. Taken together, isolation of B. pseudomallei from a soil sample and high seropositivity among patient contacts suggest at least regional endemicityof melioidosis in Puerto Rico. Increased awareness of melioidosis is needed to enable early case identification and early initiation of appropriate antimicrobial therapy.

Zika virus is a flavivirus transmitted primarily by Aedes species mosquitoes; symptoms of infection include rash, arthralgia, fever, and conjunctivitis.*,† Zika virus infection during pregnancy can cause microcephaly and other serious brain anomalies (1), and in rare cases, Zika virus infection has been associated with Guillain-Barre syndrome (2) and severe thrombocytopenia (3). This report describes the incidence of reported symptomatic Zika virus disease in the U.S. territory of Puerto Rico by age and sex. During November 1, 2015-October 20, 2016, 62,500 suspected Zika virus disease cases were reported to the Puerto Rico Department of Health (PRDH); 29,345 (47%) were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) testing, or were presumptively diagnosed based on serological testing. The highest incidence among confirmed or presumptive cases occurred among persons aged 20-29 years (1,150 cases per 100,000 residents). Among 28,219 (96.2%) nonpregnant patients with confirmed or presumptive Zika virus disease, incidence was higher among women (936 per 100,000 population) than men (576 per 100,000) for all age groups ≥20 years, and the majority (61%) of reported Zika virus disease cases occurred in females. Among suspected Zika virus disease cases in nonpregnant adults aged ≥40 years, the percentage that tested positive among females (52%) was higher than that among males (47%) (p

Zika virus is a flavivirus transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes, and infection can be asymptomatic or result in an acute febrile illness with rash (1). Zika virus infection during pregnancy is a cause of microcephaly and other severe birth defects (2). Infection has also been associated with Guillain-Barre syndrome (GBS) (3) and severe thrombocytopenia (4,5). In December 2015, the Puerto Rico Department of Health (PRDH) reported the first locally acquired case of Zika virus infection. This report provides an update to the epidemiology of and public health response to ongoing Zika virus transmission in Puerto Rico (6,7). A confirmed case of Zika virus infection is defined as a positive result for Zika virus testing by reverse transcription-polymerase chain reaction (RT-PCR) for Zika virus in a blood or urine specimen. A presumptive case is defined as a positive result by Zika virus immunoglobulin M (IgM) enzyme-linked immunosorbent assay (MAC-ELISA)* and a negative result by dengue virus IgM ELISA, or a positive test result by Zika IgM MAC-ELISA in a pregnant woman. An unspecified flavivirus case is defined as positive or equivocal results for both Zika and dengue virus by IgM ELISA. During November 1, 2015-July 7, 2016, a total of 23,487 persons were evaluated by PRDH and CDC Dengue Branch for Zika virus infection, including asymptomatic pregnant women and persons with signs or symptoms consistent with Zika virus disease or suspected GBS; 5,582 (24%) confirmed and presumptive Zika virus cases were identified. Persons with Zika virus infection were residents of 77 (99%) of Puerto Rico's 78 municipalities. During 2016, the percentage of positive Zika virus infection cases among symptomatic males and nonpregnant females who were tested increased from 14% in February to 64% in June. Among 9,343 pregnant women tested, 672 had confirmed or presumptive Zika virus infection, including 441 (66%) symptomatic women and 231 (34%) asymptomatic women. One patient died after developing severe thrombocytopenia (4). Evidence of Zika virus infection or recent unspecified flavivirus infection was detected in 21 patients with confirmed GBS. The widespread outbreak and accelerating increase in the number of cases in Puerto Rico warrants intensified vector control and personal protective behaviors to prevent new infections, particularly among pregnant women.

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 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).

Background Leptospirosis is a potentially fatal bacterial zoonosis that is endemic throughout the tropics and may be misdiagnosed as dengue. Delayed hospital admission of leptospirosis patients is associated with increased mortality. Methodology/Principal Findings During a concurrent dengue/leptospirosis epidemic in Puerto Rico in 2010, suspected dengue patients that tested dengue-negative were tested for leptospirosis. Fatal and non-fatal hospitalized leptospirosis patients were matched 1:1–3 by age. Records from all medical visits were evaluated for factors associated with fatal outcome. Among 175 leptospirosis patients identified (4.7 per 100,000 residents), 26 (15%) were fatal. Most patients were older males and had illness onset during the rainy season. Fatal case patients first sought medical care earlier than non-fatal control patients (2.5 vs. 5 days post-illness onset [DPO], p < 0.01), but less frequently first sought care at a hospital (52.4% vs. 92.2%, p < 0.01). Although fatal cases were more often diagnosed with leptospirosis at first medical visit (43.9% vs. 9.6%, p = 0.01), they were admitted to the hospital no earlier than non-fatal controls (4.5 vs. 6 DPO, p = 0.31). Cases less often developed fever (p = 0.03), but more often developed jaundice, edema, leg pain, hemoptysis, and had a seizure (p ≤ 0.03). Multivariable analysis of laboratory values from first medical visit associated with fatal outcome included increased white blood cell (WBC) count with increased creatinine (p = 0.001), and decreased bicarbonate with either increased WBC count, increased creatinine, or decreased platelet count (p < 0.001). Conclusions/Significance Patients with fatal leptospirosis sought care earlier, but were not admitted for care any earlier than non-fatal patients. Combinations of routine laboratory values predictive of fatal outcome should be considered in admission decision-making for patients with suspected leptospirosis., Author Summary Leptospirosis is a common tropical illness that results from exposure to the urine of animals infected with Leptospira bacteria. Because leptospirosis shares signs and symptoms with other common tropical illnesses such as dengue, identification of patients with leptospirosis can be challenging. Early identification of patients with leptospirosis is necessary to initiate antibiotic therapy and in some cases provide in-hospital management. During an epidemic of leptospirosis in Puerto Rico that occurred during a concomitant dengue epidemic, we identified leptospirosis patients by screening specimens from suspected dengue patients. Of 175 leptospirosis patients identified, 26 (15%) died. After comparing leptospirosis patients that died to patients of a similar age that were hospitalized but survived, we observed that fatal cases were more often sent home after their first medical visit. We next identified several routinely available laboratory values from patients’ first medical visit that were associated with patients that died. Clinicians can use such laboratory values to diagnose and hospitalize leptospirosis patients at increased risk for fatal outcome.