Sarah A. Hook

Surveillance for Lyme Disease — United States, 2008–2015

PROBLEM/CONDITION Lyme disease is the most commonly reported vectorborne disease in the United States but is geographically focal. The majority of Lyme disease cases occur in the Northeast, mid-Atlantic, and upper Midwest regions. Lyme disease can cause varied clinical manifestations, including erythema migrans, arthritis, facial palsy, and carditis. Lyme disease occurs most commonly among children and older adults, with a slight predominance among males. REPORTING PERIOD 2008-2015. DESCRIPTION OF SYSTEM Lyme disease has been a nationally notifiable condition in the United States since 1991. Possible Lyme disease cases are reported to local and state health departments by clinicians and laboratories. Health department staff conduct case investigations to classify cases according to the national surveillance case definition. Those that qualify as confirmed or probable cases of Lyme disease are reported to CDC through the National Notifiable Diseases Surveillance System. States with an average annual incidence during this reporting period of ≥10 confirmed Lyme disease cases per 100,000 population were classified as high incidence. States that share a border with those states or that are located between areas of high incidence were classified as neighboring states. All other states were classified as low incidence. RESULTS During 2008-2015, a total of 275,589 cases of Lyme disease were reported to CDC (208,834 confirmed and 66,755 probable). Although most cases continue to be reported from states with high incidence in the Northeast, mid-Atlantic, and upper Midwest regions, case counts in most of these states have remained stable or decreased during the reporting period. In contrast, case counts have increased in states that neighbor those with high incidence. Overall, demographic characteristics associated with confirmed cases were similar to those described previously, with a slight predominance among males and a bimodal age distribution with peaks among young children and older adults. Yet, among the subset of cases reported from states with low incidence, infection occurred more commonly among females and older adults. In addition, probable cases occurred more commonly among females and with a higher modal age than confirmed cases. INTERPRETATION Lyme disease continues to be the most commonly reported vectorborne disease in the United States. Although concentrated in historically high-incidence areas, the geographic distribution is expanding into neighboring states. The trend of stable to decreasing case counts in many states with high incidence could be a result of multiple factors, including actual stabilization of disease incidence or artifact due to modifications in reporting practices employed by some states to curtail the resource burden associated with Lyme disease surveillance. PUBLIC HEALTH ACTION This report highlights the continuing public health challenge of Lyme disease in states with high incidence and demonstrates its emergence in neighboring states that previously experienced few cases. Educational efforts should be directed accordingly to facilitate prevention, early diagnosis, and appropriate treatment. As Lyme disease emerges in neighboring states, clinical suspicion of Lyme disease in a patient should be based on local experience rather than incidence cutoffs used for surveillance purposes. A diagnosis of Lyme disease should be considered in patients with compatible clinical signs and a history of potential exposure to infected ticks, not only in states with high incidence but also in areas where Lyme disease is known to be emerging. These findings underscore the ongoing need to implement personal prevention practices routinely (e.g., application of insect repellent and inspection for and removal of ticks) and to develop other effective interventions.

TickNET—A Collaborative Public Health Approach to Tickborne Disease Surveillance and Research

TickNET, a public health network, was created in 2007 to foster greater collaboration between state health departments, academic centers, and the Centers for Disease Control and Prevention on surveillance and prevention of tickborne diseases. Research activities are conducted through the Emerging Infections Program and include laboratory surveys, high-quality prevention trials, and pathogen discovery.

U.S. public's experience with ticks and tick-borne diseases: Results from national HealthStyles surveys

Surveillance data indicate that tick-borne diseases (TBDs) are a substantial public health problem in the United States, yet information on the frequency of tick exposure and TBD awareness and prevention practices among the general population is limited. The objective of this study was to gain a more complete understanding of the U.S. publics experience with TBDs using data from annual, nationally representative HealthStyles surveys. There were 4728 respondents in 2009, 4050 in 2011, and 3503 in 2012. Twenty-one percent of respondents reported that a household member found a tick on his or her body during the previous year; of these, 10.1% reported consultation with a health care provider as a result. Overall, 63.7% of respondents reported that Lyme disease (LD) occurs in the area where they live, including 49.4% of respondents from the West South Central and 51.1% from the Mountain regions where LD does not occur. Conversely, in the New England and Mid-Atlantic regions where LD, anaplasmosis, and babesiosis are common, 13.9% and 20.8% of respondents, respectively, reported either that no TBDs occur in their area or that they had not heard of any of these diseases. The majority of respondents (51.2%) reported that they did not routinely take any personal prevention steps against tick bites during warm weather. Results from these surveys indicate that exposure to ticks is common and awareness of LD is widespread. Nevertheless, use of TBD prevention measures is relatively infrequent among the U.S. public, highlighting the need to better understand barriers to use of prevention measures.

Zika Virus Shedding in Semen of Symptomatic Infected Men

Background Zika virus (ZIKV) is an emerging mosquito‐borne flavivirus that has been linked to adverse birth outcomes. Previous reports have shown that person‐to‐person transmission can occur by means of sexual contact. Methods We conducted a prospective study involving men with symptomatic ZIKV infection to determine the frequency and duration of ZIKV shedding in semen and urine and to identify risk factors for prolonged shedding in these fluids. Specimens were obtained twice per month for 6 months after illness onset and were tested by real‐time reverse‐transcriptase–polymerase‐chain‐reaction (RT‐PCR) assay for ZIKV RNA and by Vero cell culture and plaque assay for infectious ZIKV. Results A total of 1327 semen samples from 184 men and 1038 urine samples from 183 men were obtained 14 to 304 days after illness onset. ZIKV RNA was detected in the urine of 7 men (4%) and in the semen of 60 (33%), including in semen samples from 22 of 36 men (61%) who were tested within 30 days after illness onset. ZIKV RNA shedding in semen decreased substantially during the 3 months after illness onset but continued for 281 days in 1 man (1%). Factors that were independently associated with prolonged RNA shedding included older age, less frequent ejaculation, and the presence of certain symptoms at the time of initial illness. Infectious ZIKV was isolated from 3 of 78 semen samples with detectable ZIKV RNA, all obtained within 30 days after illness onset and all with at least 7.0 log10 ZIKV RNA copies per milliliter of semen. Conclusions ZIKV RNA was commonly present in the semen of men with symptomatic ZIKV infection and persisted in some men for more than 6 months. In contrast, shedding of infectious ZIKV appeared to be much less common and was limited to the first few weeks after illness onset. (Funded by the Centers for Disease Control and Prevention.)

Pet ownership increases human risk of encountering ticks

We examined whether pet ownership increased the risk for tick encounters and tickborne disease among residents of three Lyme disease‐endemic states as a nested cohort within a randomized controlled trial. Information about pet ownership, use of tick control for pets, property characteristics, tick encounters and human tickborne disease were captured through surveys, and associations were assessed using univariate and multivariable analyses. Pet‐owning households had 1.83 times the risk (95% CI = 1.53, 2.20) of finding ticks crawling on and 1.49 times the risk (95% CI = 1.20, 1.84) of finding ticks attached to household members compared to households without pets. This large evaluation of pet ownership, human tick encounters and tickborne diseases shows that pet owners, whether of cats or dogs, are at increased risk of encountering ticks and suggests that pet owners are at an increased risk of developing tickborne disease. Pet owners should be made aware of this risk and be reminded to conduct daily tick checks of all household members, including the pets, and to consult their veterinarian regarding effective tick control products.

Lyme Disease Surveillance in New York State: an Assessment of Case Underreporting.

Despite the mandatory nature of Lyme disease (LD) reporting in New York State (NYS), it is believed that only a fraction of the LD cases diagnosed annually are reported to public health authorities. Lack of complete LD case reporting generally stems from (i) lack of report of provider‐diagnosed cases where supportive laboratory testing is not ordered or results are negative (i.e. provider underreporting) and (ii) incomplete case information (clinical laboratory reporting only with no accompanying clinical information) such that cases are considered ‘suspect’ and not included in national and statewide case counts (i.e. case misclassification). In an attempt to better understand LD underreporting in NYS, a two‐part study was conducted in 2011 using surveillance data from three counties. Case misclassification was assessed by obtaining medical records on suspect cases and reclassifying according to the surveillance case definition. To assess provider underreporting, lists of patients for whom ICD‐9‐CM code 088.81 (LD) had been used were reported to NYS Department of Health (NYSDOH). These lists were matched to the NYSDOH case reporting system, and medical records were requested on patients not previously reported; cases were then classified according to the case definition. When including both provider underreporting and case misclassification, approximately 20% (range 18.4–24.6%) more LD cases were identified in the three‐county study area than were originally reported through standard surveillance. The additional cases represent a minimum percentage of unreported cases; the true percentage of unreported cases is likely higher. Unreported cases were more likely to have a history of erythema migrans (EM) rash and were more likely to be young paediatric cases. Results of the study support the assertion that LD cases are underreported in NYS. Initiatives to increase reporting should highlight the importance of reporting clinically diagnosed EM and be targeted to those providers most likely to diagnose LD, specifically providers treating paediatric patients.

Assessing diagnostic coding practices among a sample of healthcare facilities in Lyme disease endemic areas: Maryland and New York – A Brief Report

The value of using diagnostic codes in Lyme disease (LD) surveillance in highly endemic states has not been well studied. Surveys of healthcare facilities in Maryland (MD) and New York (NY) regarding coding practices were conducted to evaluate the feasibility of using diagnostic codes as a potential method for LD surveillance. Most respondents indicated that their practice utilized electronic medical records (53%) and processed medical/billing claims electronically (74%). Most facilities were able to search office visits associated with specific ICD‐9‐CM and CPT codes (74% and 73%, respectively); no discernible differences existed between the healthcare facilities in both states. These codes were most commonly assigned by the practitioner (82%), and approximately 70% of respondents indicated that these codes were later validated by administrative staff. These results provide evidence for the possibility of using diagnostic codes in LD surveillance. However, the utility of these codes as an alternative to traditional LD surveillance requires further evaluation.

Exploring an alternative approach to Lyme disease surveillance in Maryland

In Maryland, Lyme disease (LD) is a reportable disease and all laboratories and healthcare providers are required to report to the local health department. Given the volume of LD reports and effort required for investigation, surveillance for LD is burdensome and subject to underreporting. We explored the utility of International Classification of Diseases, 9th Revision, Clinical Modification (administrative) codes for use with LD surveillance. We aimed to collect the administrative codes for a 10% sample of 2009 LD reports (n = 474) from 292 facilities stratified by case classification (confirmed, probable, suspected and not a case). Sixty‐three per cent (n = 184) of facilities responded to the survey, and 341 different administrative codes were obtained for 91% (n = 430) of sampled reports. The administrative code for Lyme disease (088.81) was the most commonly reported code (133/430 patients) among sampled reports; while it was used for 62 of 151 (41%) confirmed cases, it was also used for 48 of 192 (25%) not a case reports (sensitivity 41% and specificity 73%). A combination of nine codes was developed with sensitivity of 74% and specificity of 37% when compared to not a case reports. We conclude that the administrative code for LD alone has low ability to identify LD cases in Maryland. Grouping certain codes improved sensitivity, but our results indicate that administrative codes alone are not a viable surveillance alternative for a disease with complex manifestations such as LD.

Impacts of misclassification on Lyme disease surveillance

In Maryland, Lyme disease (LD) is the most widely reported tickborne disease. All laboratories and healthcare providers are required to report LD cases to the local health department. Given the large volume of LD reports, the nuances of diagnosing and reporting LD, and the effort required for investigations by local health department staff, surveillance for LD is burdensome and subject to underreporting. To determine the degree to which misclassification occurs in Maryland, we reviewed medical records for a sample of LD reports from 2009. We characterized what proportion of suspected and “not a case” reports could be reclassified as confirmed or probable once additional information was obtained from medical record review, explored the reasons for misclassification, and determined multipliers for a more accurate number of LD cases. We reviewed medical records for reports originally classified as suspected (n = 44) and “not a case” (n = 92). Of these 136 records, 31 (23%) suspected cases and “not a case” reports were reclassified. We calculated multipliers and applied them to the case counts from 2009, and estimate an additional 269 confirmed and probable cases, a 13.3% increase. Reasons for misclassification fell into three general categories: lack of clinical or diagnostic information from the provider; surveillance process errors; and incomplete information provided on laboratory reports. These multipliers can be used to calculate a better approximation of the true number of LD cases in Maryland, but these multipliers only account for underreporting due to misclassification, and do not account for cases that are not reported at all (e.g., LD diagnoses based on erythema migrans alone that are not reported) or for cases that are not investigated. Knowing that misclassification of cases occurs during the existing LD surveillance process underscores the complexities of LD surveillance, which further reinforces the need to find alternative approaches to LD surveillance.

Lyme disease surveillance in the United States: Looking for ways to cut the Gordian knot

Current surveillance methods have been useful to document geographic expansion of Lyme disease in the United States and to monitor the increasing incidence of this major public health problem. Nevertheless, these approaches are resource‐intensive, generate results that are difficult to compare across jurisdictions, and measure less than the total burden of disease. By adopting more efficient methods, resources could be diverted instead to education of at‐risk populations and new approaches to prevention. In this special issue of Zoonoses and Public Health, seven articles are presented that either evaluate traditional Lyme disease surveillance methods or explore alternatives that have the potential to be less costly, more reliable, and sustainable. Twenty‐five years have passed since Lyme disease became a notifiable condition – it is time to reevaluate the purpose and goals of national surveillance.