The 2017 Puerto Rico leptospirosis outbreak was an outbreak of leptospirosis that affected Puerto Rico in the fall of 2017, following Hurricane Maria's landfall. Background Leptospirosis, caused by an infection of Leptospira bacteria, is most commonly transmitted via contaminated water supplies, with over 870,000 cases and 49,000 deaths reported annually. Caribbean islands, such as Puerto Rico, have among the highest incidence rates of the disease, with climate, geographic, and socioeconomic factors interacting to increase population risk.
Infection develops following exposure to water or soil containing the bacteria, which is often found in the urine or feces of infected animals—most commonly livestock, rodents or pets. The global prevalence of leptospirosis is projected to rise in line with demographic shifts that increase the number of poor, urban residents in tropical regions affected by climate change.
Cases of infectious diseases, including leptospirosis, often spike in the aftermath of intense storms, due to flooding and damage of infrastructure. Diseases transmitted from animals to humans are collectively known as zoonotic diseases. Urban expansion into undeveloped areas has increased human contact with rodent habitats, creating additional pathways for leptospirosis transmission, especially during heavy rainfall or other inclement weather.Lau et al. 2010
The delayed onset of symptoms of leptospirosis can make it difficult to detect. After an incubation period of typically 5 to 10 days, but potentially as early as 2 days and up to 30 days after infection, people infected with Leptospira bacteria can develop flu-like symptoms including fever, chills, headache, myalgia (muscle pain), cough, vomiting, and diarrhea. The early signs of the disease are vague and often too general for a confident diagnosis of leptospirosis. In some cases, patients may present with only mild illness with other differentials considered, including meningitis, influenza, sepsis, and many others. Other patients will present with the fulminant infection, exhibiting signs of end stage liver failure, acute renal failure, or severe pulmonary hemorrhage syndrome (SPHS).
The test considered to be the gold standard for leptospirosis diagnosis by the World Health Organization (WHO) is not very sensitive in the early stages of the disease, before the body has had a chance to mount an immune response. This test, the microagglutination test (MAT), is a serologic test that measures the level of antibodies created by the immune system in response to the leptospira bacteria. Although this test has high specificity, it has low sensitivity, limiting its ability to identify infected individuals. Doctors will typically submit paired serum samples from both early and later in the course of illness in order to demonstrate a four-fold rise in titer, an indication of a positive result. Additionally, individuals living in a leptospira-endemic region may have a relatively high initial MAT test that only indicates previous infection, not necessarily disease. Commonly, clinicians will submit blood and urine for polymerase chain reaction (PCR) testing, though it is often time-sensitive as samples should be collected before antibiotic treatment and there is typically a 1-to-5-day delay in results, depending on the lab used. In regions with limited laboratory capacity, clinicians often rely on clinical judgment and epidemiologic context, which can delay targeted treatment during outbreaks. Budihal & Perwez 2014
Outbreak
Following the hurricane, large areas of Puerto Rico were without tap water, forcing residents to use other sources of water, such as streams. Since leptospirosis is contracted through water contaminated with animal urine, it is possible this is how people contracted the disease. By October 23, four people were suspected to have died from the disease, while 74 others were suspected to be infected. There were 18 confirmed cases, 4 confirmed deaths, and 99 suspected cases by November 7. This was a rapid increase from Puerto Rico's typical average of 5 cases of leptospirosis per month. Despite the possibility there had been an outbreak, officials did not deem the situation dire. Researchers in public health found that the hurricane response used inconsistent reporting systems, making it harder to detect new cases.CNN & CPI 2018
In July 2018, CNN, in collaboration with the Center for Investigative Journalism (CPI), published an online article in which seven disease experts reviewed an official Puerto Rico government mortality database. The data reviewed included 57 laboratory-confirmed cases of leptospirosis in 2017. Of those, 54 of them were reported after Hurricane Maria made landfall on 20 September 2017. The number of laboratory-confirmed cases amounted to at least a three-fold increase in cases compared to 2016 and 2015. The experts all agreed that, since the records listed such a large number of confirmed cases of leptospirosis, Puerto Rico officials should have declared an epidemic or an outbreak after Hurricane Maria.
Responses Many of Puerto Rico's essential public health, health care, and other government services were rendered inoperative in the immediate aftermath of Hurricane Maria. Two weeks after the storm, only 5% of electrical power had been restored to the island, 11% of cell phone towers had been fixed, approximately 50% of the supermarkets were open, 9 of 69 hospitals had been connected back to the electric grid, and less than 50% of water services had been re-established. The slow pace of recovery from the storm itself fueled public anger toward the Puerto Rican and U.S. governments for failing to prioritize the island's urgent needs.
As reports of a spike in leptospirosis cases and deaths in Puerto Rico spread, the government came under heavy criticism for its response, or lack thereof, to news of a potential outbreak. Territorial officials were blamed for the perceived failure to properly equip disaster response workers who had to operate in flood waters, delays in laboratory testing to confirm leptospirosis cases (both among patients undergoing treatment and deceased individuals), and an unwillingness to report morbidity and mortality data related to leptospirosis once there was increased public scrutiny in response to the rise in deaths. According to emergency responders, communication outages increased the difficulty of coordinating specimen transport and receiving laboratory updates.Concepción-Acevedo et al. 2018
Despite criticism by the public, the Puerto Rico Department of Public Health (PRDOH) denies the claim of a poor response. PRDOH, with their main lab in San Juan, typically provides lab testing and surveillance of disease in the areas affected by Hurricane Maria. There are ancillary facilities located in Arecibo, Ponce, and Mayaguez. PRDOH requested assistance from the Centers for Disease Control and Prevention (CDC), the CDC Foundation, and the Association of Public Health Laboratories (APHL) during the aftermath. It is reported that there was severe damage to the laboratory facilities, specifically three essential lab sectors, including the electrical power supply for the facility, physical structure of the laboratory, and damage to the equipment and chemical reagents from power loss and water leaks. The lab was able to create a temporary solution to transport samples from Puerto Rico in the direct aftermath of Hurricane Maria to the U.S. for surveillance and diagnostic testing, thereby allowing the continual surveillance and diagnosis of high priority diseases during the rebuilding of the PRDOH facility and the restoration of essential laboratory services.
The CDC reported several challenges associated with this temporary system, including the inconsistent shipping availability to the United States, reliance on a single generator to power the remaining PRDOH laboratory and communications (fax), and availability of appropriate specimen containers. Despite the challenges, the CDC reported successful transport and shipping of over 1,700 samples in 4 months and the identification of close to 350 cases referred to as 'high-priority infectious disease,' including leptospirosis.
Public health implications Outbreak monitoring and surveillance Like most densely inhabited tropical islands, Puerto Rico has high concentrations of risk factors for zoonotic diseases such as leptospirosis. Throughout the Caribbean, widespread poverty, a hot and steadily warming climate, invasive species, tourism, and lack of adequate infrastructure contribute to the persistence of endemic tropical diseases. Syndromic surveillance tools for tracking clusters of febrile or respiratory illnesses have been recommended as low-resource methods for flagging potential early outbreaks.Oda et al. 2018
Leptospirosis outbreaks have occurred in Puerto Rico in previous years. In 1996, Hurricane Hortense caused serious damage and flooding on the island that led to a four-fold increase in leptospirosis cases and many deaths. During the lead-up to Hurricane Maria, however, many health care providers later reported that they were not notified about the need to monitor and test for the illness. This failure to detect an increase in cases early on likely contributed to the illnesses and deaths that sparked public outcry.
Given these gaps in detection, it is likely that improved disease monitoring and testing could have helped prevent the storm-associated rise in leptospirosis deaths. Choosing the best methods for surveillance in this case can be vexing. Leptospirosis, in addition to being highly variable in disease expression, can pose the added challenge of showing few clinical signs in infected individuals for weeks at a time. Because initial symptoms are indistinguishable from many other common illnesses and often do not progress beyond fever and gastrointestinal signs in terms of severity, most infections go unrecognized.
The experiences of medical and public health responders point the way toward potential improvements in leptospirosis monitoring and surveillance strategies. The U.S. Department of Veterans Affairs (VA) and CDC, which operate in multiple health campuses throughout Puerto Rico, established enhanced laboratory-based surveillance after the hurricane hit in order to monitor various infections at VA facilities for the possibility of an outbreak. Enhanced surveillance by the VA detected two DNA-confirmed cases of leptospirosis following the storm. In addition to laboratory testing of disease cases, the VA tracked groupings of infectious disease syndromes, such as pneumonia and gastrointestinal illness, as the number of total visits to emergency departments to try to identify trends for improved planning and resource allocation.
A study of disease surveillance in Puerto Rico after a period of floods caused by Hurricane Hortense in 1996 found an increase in leptospirosis infections that were caught by laboratory tests for dengue fever. The dengue tests found leptospirosis that otherwise would have most likely gone undetected and possibly fatal in some cases. This finding supports the need for readily available field laboratory testing for leptospirosis during flooding and other disruptive hydrologic events.