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During 2005, 49 states and Puerto Rico reported 6,417 cases of rabies in nonhuman animals and 1 case in a human being to the CDC, representing a 6.2% decrease from the 6,836 cases in nonhuman animals and 8 cases in human beings reported in 2004. Approximately 92% of the cases were in wildlife, and 8% were in domestic animals. Relative contributions by the major animal groups were as follows: 2,534 raccoons (39.5%), 1,478 skunks (23%), 1,408 bats (21.9%), 376 foxes (5.9%), 269 cats (4.2%), 93 cattle (1.5%), and 76 dogs (1.2%). Compared with numbers of reported cases in 2004, cases in 2005 decreased among all groups, except bats, horses, and other wild animals. Decreases in numbers of rabid raccoons during 2005 were reported by 10 of the 20 eastern states in which raccoon rabies was enzootic and decreased overall by 1.2%, compared with 2004. On a national level, the number of rabies cases in skunks during 2005 decreased 20.4% from the number reported in 2004. Once again, Texas reported the greatest number (n = 392) of rabid skunks and the greatest overall state total of rabies cases (741). Texas reported no cases of rabies associated with the dog/coyote rabies virus variant and only 8 cases associated with the Texas gray fox rabies virus variant (compared with 22 cases in 2004). The total number of cases of rabies reported nationally in foxes decreased 3.3%, compared with those reported in 2004. The 1,408 cases of rabies reported in bats represented a 3.5% increase over numbers reported in 2005. Cases of rabies in cats, dogs, cattle, and sheep and goats decreased 4.3%, 19.2%, 19.1%, and 10%, respectively, whereas cases reported in horses and mules increased 9.3%. In Puerto Rico, reported cases of rabies in mongooses increased 29.8%, and rabies in domestic animals decreased 37.5%. One case of human rabies was reported from Mississippi during 2005. This case was submitted by the state to the CDC's unexplained deaths project and diagnosed as rabies retrospectively. [ABSTRACT FROM AUTHOR]

During 2004, 49 states and Puerto Rico reported 6,836 cases of rabies in nonhuman animals and 8 cases in human beings to the CDC, representing a 4.6% decrease from the 7,170 cases in nonhuman animals and 3 cases in human beings reported in 2003. Approximately 92% of the cases were in wildlife, and 8% were in domestic animals (compared with 91% and 9%, respectively, in 2003). Relative contributions by the major animal groups were as follows: 2,564 raccoons (37.5%), 1,856 skunks (27.1%), 1,361 bats (19.9%), 389 foxes (5.7%), 281 cats (4.1%), 115 cattle (1.7%), and 94 dogs (1.4%). Compared with the numbers of reported cases in 2003, cases in 2004 decreased among all groups, except bats, cattle, human beings, and ‘other domestics’ (1 llama). Decreases in numbers of rabid raccoons during 2004 were reported by 12 of the 20 eastern states in which raccoon rabies was enzootic. In the East, Massachusetts reported the first cases of raccoon rabies detected beyond the Cape Cod oral rabies vaccine barrier. Along the western edge of the raccoon rabies epizootic (Ohio in the north and Tennessee in the south), cases of rabies were reported from unexpected new foci beyond oral rabies vaccine zones. On a national level, the number of rabies cases in skunks during 2004 decreased by 12.1% from the number reported in 2003. Once again, Texas reported the greatest number (n 534) of rabid skunks and the greatest over-all state total of rabies cases (913). Texas reported only 1 case of rabies in a dog that was infected with the dog/coyote rabies virus variant and only 22 cases associated with the Texas gray fox rabies virus variant (compared with 61 cases in 2003). The total number of cases of rabies reported nationally in foxes and raccoons declined 14.7% and 2.7%, respectively, during 2004. The 1,361 cases of rabies reported in bats during 2004 represented a 12.3% increase over the previous year's total of 1,212 cases for this group of mammals Cases of rabies reported in cats, dogs, horses and mules, and sheep and goats decreased 12.5%, 19.7%, 31.8%, and 16.7%, respectively, whereas cases reported in cattle increased 17.4%. In Puerto Rico, reported cases of rabies in mongooses decreased 4.1% and rabies in dogs (9 cases) remained unchanged from those reported in 2003. Among the 8 cases of rabies in human beings, 1 person from Oklahoma and 3 from Texas died following receipt of infected organs and tissues from an Arkansas donor. In California, a person originally from El Salvador and, in Florida, a person originally from Haiti both died of canine rabies infections acquired outside the United States In Wisconsin, a teenager contracted rabies from a bat bite and became the first known person to survive rabies despite not having received rabies vaccine prior to symptom onset. [ABSTRACT FROM AUTHOR]

During 2002, 49 states and Puerto Rico reported 7,967 cases of rabies in nonhuman animals and 3 cases in human beings to the Centers for Disease Control and Prevention, an increase of 7.2% from the 7,436 cases in nonhuman animals and 1 case in a human being reported in 2001. More than 92% (7,375 cases) were in wild animals, whereas 7.4% (592) were in domestic species (compared with 93.3% in wild animals and 6.7% in domestic species in 2001). Compared with cases reported in 2001, the numbers of cases reported in 2002 increased among all major reporting groups with the exception of swine and rodents and lagomorphs. The relative contributions of the major groups of animals were as follows: raccoons (36.3%; 2,891 cases), skunks (30.5%; 2,433), bats (17.2%; 1,373), foxes (6.4%; 508), cats (3.8%; 299), dogs (1.2%; 99), and cattle (1.5%; 116). Thirteen of the 19 states in which the raccoon associated variant of the rabies virus has been enzootic reported increases in the numbers of rabid raccoons during 2002. Among those states that have engaged in wildlife rabies control programs, Ohio reported 1 case of raccoon rabies associated with the epizootic of rabies in raccoons and 1 case in an equid that was infected with a bat variant of the rabies virus, compared with 2 cases reported in terrestrial animals during 2001. Texas reported no cases of rabies associated with the dog/coyote variant of the rabies virus (compared with 1 case in 2001) and 65 cases associated with the gray fox variant of the virus (an increase of 225% from 20 cases reported in 2001). In Massachusetts and Rhode Island, states with enzootic raccoon rabies, reports of rabid skunks again exceeded those of rabid raccoons (the sixth consecutive year, although in Rhode Island, this difference decreased to only 7 more skunks than raccoons [38/31]). Tennessee reported a single case of raccoon rabies in a pet raccoon from the central part of the state; the captive animal had been transported to Tennessee from northern Georgia. Nationally, the number of rabies cases in skunks during 2002 increased by 6.6% over those reported in 2001. Texas reported the greatest number (740) of rabid skunks and the greatest overall state total of rabies cases (1,049) during 2002. The 1,373 cases of rabies reported in bats during 2002 surpassed the previous year's record (1,281 cases) as the largest number of reported cases ever recorded for this group of mammals. Cases of rabies reported in cats (299), cattle (116), and dogs (99) increased by 10.7%, 41.5%, and 11.24%, respectively, from 2001 to 2002. Rabies among sheep and goats increased 400% from 3 cases in 2001 to 15 in 2002, and cases among horses and mules increased 13.7% (51 cases in 2001 to 58 in 2002). Reported cases of rabies in mongooses in Puerto Rico decreased 4.3% from the previous year (70 cases in 2001 to 67 cases in 2002), while cases of rabies in dogs increased 7.7% (13 to 14). [ABSTRACT FROM AUTHOR]

Presents a study that described the epizootiology of skunk rabies in the eastern U.S. Background on skunk rabies; Materials and methods; Results of the study.

Epidemiologic and clinical characteristics of fatal and nonfatal cases of Rocky Mountain spotted fever (RMSF) were compared to identify risk factors for death caused by this disease. Confirmed and probable RMSF cases reported through US national surveillance for 1981-- 1998 were analyzed. Among 6388 RMSF patients, 213 died (annual case-fatality rate, 3.3%; range, 4.9% in 1982 to 1.1% in 1996). Use of tetracycline-class antibiotics for treatment of RMSF increased significantly in the 1990s, compared with use in the 1980s. Older patients, patients treated with chloramphenicol only, patients for whom tetracycline antibiotics were not the primary therapy, and patients for whom treatment was delayed >5 days after the onset of symptoms were at higher risk for death. Although the case-fatality rate was lower in the 1990s than in the 1980s, risk factors for fatal RMSF were similar. Despite the availability of effective antibiotics, RMSF-related deaths continue to occur because of delayed diagnosis and failure to use appropriate therapy. [ABSTRACT FROM AUTHOR]

Purpose: To summarize the epidemiologic, diagnostic, and clinical features of the 32 laboratory-confirmed cases of human rabies diagnosed in the United States from 1980 to 1996.Data Sources: Data were obtained from case reports of human rabies submitted to the Centers for Disease Control and Prevention by state or local health authorities.Study Selection: All cases of human rabies reported in the United States from 1980 to 1996 in which infection with rabies virus was confirmed by laboratory studies.Data Extraction: Patients were reviewed for demographic characteristics, exposure history, rabies prophylaxis, clinical presentation, treatment, clinical course, diagnostic laboratory tests, identification of rabies virus variants, and the number of medical personnel or family members who required postexposure prophylaxis after coming in contact with an exposed person.Data Synthesis: 32 cases of human rabies were reported from 20 states. Patients ranged in age from 4 to 82 years and were predominantly male (63%). Most patients (25 of 32) had no definite history of an animal bite or other event associated with rabies virus transmission. Of the 32 cases, 17 (53%) were associated with rabies virus variants found in insectivorous bats, 12 (38%) with variants found in domestic dogs outside the United States, 2 (6%) with variants found in indigenous domestic dogs, and 1 (3%) with a variant found in indigenous skunks. Among the 7 patients with a definite exposure history, 6 cases were attributable to dog bites received in foreign countries and 1 was attributable to a bat bite received in the United States. In 12 of the 32 patients (38%), rabies was not clinically suspected and was diagnosed after death. In the remaining 20 cases (63%), the diagnosis of rabies was considered before death and samples were obtained specifically for laboratory confirmation a median of 7 days (range, 3 to 17 days) after the onset of clinical signs. Of the clinical differences between patients in whom rabies was diagnosed before death and those in whom it was diagnosed after death, the presence of hydrophobia or aerophobia was significantly associated with antemortem diagnosis (odds ratio, 11.0 [95% CI, 1.05 to 273.34]). The median number of medical personnel or familial contacts of the patients who received postexposure prophylaxis was 54 per patient (range, 4 to 179). None of the 32 patients with rabies received postexposure prophylaxis before the onset of clinical disease.Conclusions: In the United States, human rabies is rare but probably underdiagnosed. Rabies should be included in the differential diagnosis of any case of acute, rapidly progressing encephalitis, even if the patient does not recall being bitten by an animal. In addition to situations involving an animal bite, a scratch from an animal, or contact of mucous membranes with infectious saliva, postexposure prophylaxis should be considered if the history indicates that a bat was physically present, even if the person is unable to reliably report contact that could have resulted in a bite. Such a situation may arise when a bat bite causes an insignificant wound or the circumstances do not allow recognition of contact, such as when a bat is found in the room of a sleeping person or near a previously unattended child. [ABSTRACT FROM AUTHOR]

In March 2002, typhus fever was diagnosed in two patients residing in West Virginia and Georgia. Both patients were hospitalized with severe febrile illnesses, and both had been recently exposed to or had physical contact with flying squirrels or flying squirrel nests. Laboratory results indicated Rickettsia prowazekii infection. [ABSTRACT FROM AUTHOR]

The increased incidence of Rocky Mountain spotted fever (RMSF) in 1997–2002 compared with previous years may be related to enhanced awareness and reporting of RMSF as well as changes in human–vector interaction. However, reports on RMSF mortality underscore the need for physician vigilance in considering a diagnosis of RMSF for febrile individuals potentially exposed to ticks and stress the importance of treating such persons regardless of the presence of a rash. [ABSTRACT FROM AUTHOR]

Ehrlichia chaffeensis causes human monocytic ehrlichiosis, and Anaplasma phagocytophilum causes human granulocytic anaplasmosis. These related tick-borne rickettsial organisms can cause severe and fatal illness. During 2000-2007, the reported incidence rate of E. chaffeensis increased from 0.80 to 3.0 cases/million persons/year. The case-fatality rate was 1.9%, and the hospitalization rate was 49%. During 2000-2007, the reported incidence of A. phagocytophilum increased from 1.4 to 3.0 cases/million persons/year. The case-fatality rate was 0.6%, and the hospitalization rate was 36%. Rates among female patients were lower than among male patients for ehrlichiosis (rate ratio = 0.68) and anaplasmosis (rate ratio = 0.70). Most (80%) ehrlichiosis and anaplasmosis cases met only a probable case definition, although, use of a polymerase chain reaction to confirm infections increased during 2000-2007. Heightened reporting of these diseases will likely continue with improving recognition, changing surveillance practices, and appropriate application of diagnostic assays.

Rocky Mountain spotted fever (RMSF), a potentially fatal tick-borne infection caused by Rickettsia rickettsii, is considered a notifiable condition in the United States. During 2000 to 2007, the annual reported incidence of RMSF increased from 1.7 to 7 cases per million persons from 2000 to 2007, the highest rate ever recorded. American Indians had a significantly higher incidence than other race groups. Children 5-9 years of age appeared at highest risk for fatal outcome. Enzyme-linked immunosorbent assays became more widely available beginning in 2004 and were used to diagnose 38% of cases during 2005-2007. The proportion of cases classified as confirmed RMSF decreased from 15% in 2000 to 4% in 2007. Concomitantly, case fatality decreased from 2.2% to 0.3%. The decreasing proportion of confirmed cases and cases with fatal outcome suggests that changes in diagnostic and surveillance practices may be influencing the observed increase in reported incidence rates.

Rocky Mountain spotted fever (RMSF) is the most commonly reported fatal tick-borne disease in the United States. During 1997-2002, 3,649 cases of RMSF were reported to the Centers for Disease Control and Prevention via the National Electronic Telecommunications System for Surveillance; 2,589 case report forms, providing supplemental information, were also submitted. The average annual RMSF incidence during 1997-2002 was 2.2 cases/million persons. The annual incidence increased during 1997-2002 to a rate of 3.8 cases/million persons in 2002. The incidence was lowest among persons aged<5 and 10-29 years, and highest among adults aged 60-69 years. The overall case-fatality rate was 1.4%; the rate peaked in 1998 at 2.9% and declined to 0.7% in 2001 and 2002. Children<5 years of age had a case-fatality rate (5%) that was significantly greater than the rates for age groups<60 years of age, except for that for 40-49 years of age. Continued national surveillance is needed to assess the effectiveness of prevention efforts and early treatment in decreasing severe morbidity and mortality associated with RMSF.

During 2001 through 2002, 1,176 cases of the tick-borne diseases human monocytic ehrlichiosis (HME) and human granulocytic anaplasmosis (HGA) were reported to the Centers for Disease Control and Prevention (CDC) by 32 states through the National Electronic Telecommunications System for Surveillance. The average reported annual incidences for HME and HGA during 2001-2002 were 0.6 and 1.4 cases per million population, respectively; incidence was highest among men > 60 years of age. During this same interval, a total of 883 cases of HME and HGA were reported to CDC through a passive surveillance system of tick-borne disease case report forms (CRFs). The surveillance information retrieved from CRFs has allowed for qualitative evaluation of ehrlichiosis and anaplasmosis risk factors, severity, and diagnostic accuracy. Although these surveillance systems likely substantially under-represent the true burden of ehrlichiosis and anaplasmosis in the United States due to poor recognition and reporting, they represent the first compilation of national data since these diseases were made nationally notifiable. Continued and improved surveillance activities will progressively reinforce our understanding and awareness of these newly recognized zoonotic infections.

During 2003, 49 states and Puerto Rico reported 7,170 cases of rabies in nonhuman animals and 3 cases in human beings to the CDC. This represents a 10% decrease from the 7,967 cases in nonhuman animals and 3 cases in human beings reported in 2002. More than 91 (n = 6,556) were in wild animals, and 8.6% (614) were in domestic species (compared with 92.5% in wild animals and 74% in domestic species in 2002). The relative contributions of the major groups of animals were as follows: 2,635 raccoons (36.7%), 2,112 skunks (29.4%), 1,212 bats (16.9%), 456 foxes (6.4%), 321 cats (4.5%), 117 dogs (1.6%), and 98 cattle (1.4%). Compared with cases reported in 2002, the number of cases reported in 2003 decreased among all reporting groups with the exception of cats, dogs, equids, and swine. Ten of the 19 states with enzootic rabies in raccoons, the District of Columbia, and New York City reported decreases in the numbers of rabid raccoons during 2003. Tennessee reported 4 cases of indigenous rabies in raccoons during 2003, becoming the 20th state where rabies in raccoons is known to be enzootic. On a national level, the number of rabies cases in skunks during 2003 decreased by 13.2% from those reported in 2002. Texas again reported the greatest number (n = 620) of rabid skunks during 2003, as well as the greatest overall state total of rabies cases (909). As in 2002, Texas did not report any cases of rabies associated with the dog/coyote variant of the rabies virus, but did report 61 cases associated with the gray fox variant of the virus (compared with 65 cases in 2002). The 1,212 cases of rabies reported in bats during 2003 represented a decline of nearly 12% from the previous year's record high of 1,373 cases for this group of mammals. Cases of rabies reported in foxes.and raccoons declined 10.2% and 8.9%, respectively, during 2003. Rabies among sheep and goats decreased from 15 cases in 2002 to 12 cases in 2003, whereas cases reported in cats, dogs, and equids increased 74%, 18.2%, and 8.6%, respectively. In Puerto Rico, reported cases of rabies in mongooses and dogs decreased 26.9% and 35.7%, respectively, from those reported in 2002. Three cases of rabies in human beings were reported in California, Virginia, and Puerto Rico during 2003. The Virginia case was the first reported occurrence of rabies in a human being infected with the raccoon rabies virus variant; however, the exposure history was unknown. The California and Puerto Rico cases were the result of infections with bat and dog/mongoose rabies virus variants, respectively, and each patient had a history of a bite.

This report describes the data accumulated during the first 5 years of national surveillance for the human ehrlichioses in the United States and territories, from its initiation in 1997 through 2001. Reported cases of human monocytic and granulocytic ehrlichiosis (HME and HGE) and cases of "other ehrlichiosis" (OE), where the agent was unspecified, originated from 30 states. As anticipated, most HME cases were from the south-central and southeastern United States, while HGE was most commonly reported from the northeastern and upper-Midwestern region. State-level incident reports of 487 HME, 1,091 HGE, and 11 OE cases were evaluated. The average annual incidences of HME, HGE, and OE per million persons residing in states reporting disease were 0.7, 1.6, and 0.2, respectively. The median ages of HME (53 yr) and HGE cases (51 yr) were consistent with published patient series. Most (> 57%) ehrlichiosis patients were male. The results suggest that national surveillance for the ehrlichioses, although imperfect in coverage, will help define endemic regions and may be useful for monitoring long-term trends. Although the data appear representative of the demographic profiles established for HME and HGE, rigorous evaluation of the system is required. Methods are proposed for evaluating the quality and representativeness of HME and HGE surveillance data, using well-established surveillance systems for Rocky Mountain spotted fever and Lyme disease.

Most cases of rabies reported annually in the United States occur among three groups of carnivores--raccoons (Procyon lotor), skunks (Mephitis, Spilogale, and Putorius), foxes (Vulpes, Urocyon, and Alopex)--and among bats (numerous species). However, between 1960 and 2000, a total of 2,851 cases of rabies in 17 other carnivore taxa were reported to the Centers for Disease Control and Prevention, Atlanta, Georgia (USA), from 49 states, the District of Columbia, and Puerto Rico. Three species of these other carnivores (mongooses [Herpestes javanicus], coyotes [Canis latrans], and bobcats [Lynx rufus]) accounted for 92% (2,624/2,851) of the cases reported among other canivorous mammals (OCMs). Most OCMs demonstrated temporal or spatial variation in numbers of reported cases. Tests of specimens from OCMs infected in the United States identified variants of the rabies virus that corresponded with variants associated with the major terrestrial reservoirs within their respective regions of origin. Variants of the rabies virus in samples from mongooses in Puerto Rico could not be distinguished from those in samples from dogs in Puerto Rico by virus typing methods.

Objective: To describe surveillance trends and epidemiologic features of rabies in bats in the United States, focusing on 3 bat species primarily associated with variants of the rabies virus that affect humans., Design: Retrospective study., Animals: 31,380 bats., Procedure: Data on rabies for bats identified to species and reported by state laboratories from 1993 to 2000 were analyzed, focusing on silver-haired, eastern pipistrelle, and Brazilian free-tailed bats. Categoric variables were derived from other provided information., Results: Data were reported from 37 states during the study interval; complete species-specific data were not reported by any state for the entire interval. Bats primarily associated with rabies virus variants affecting humans were more likely to yield positive test results for rabies (22.7%), compared with all other bats (5.5%) in most seasons and from most regions of the United States. However, certain other bat species had higher percentages of positive results. Risk of positive results was highest in the fall and highest among bats originating in the southwestern United States., Conclusions and Clinical Relevance: Increased risk of rabies among certain groups of bat species was consistently found across seasons and most geographic regions of the United States. Results were in general agreement with those of previous studies conducted within smaller geographic regions. There are ongoing efforts to improve surveillance of rabies in bats, although surveillance is incomplete in some regions.

During 2001, 49 states and Puerto Rico reported 7,437 cases of rabies in nonhuman animals and 1 case in a human being to the Centers for Disease Control and Prevention, an increase of < 1% from 7,364 cases in nonhuman animals and 5 human cases reported in 2000. More than 93% (6,939 cases) were in wild animals, whereas 6.7% (497 cases) were in domestic species (compared with 93.0% in wild animals and 6.9% in domestic species in 2000). The number of cases reported in 2001 increased among bats, cats, skunks, rodents/lagomorphs, and swine and decreased among dogs, cattle, foxes, horses/mules, raccoons, and sheep/goats. The relative contributions of the major groups of animals were as follows: raccoons (37.2%; 2,767 cases), skunks (30.7%; 2,282), bats (17.2%; 1,281), foxes (5.9%; 437), cats (3.6%; 270), dogs (1.2%; 89), and cattle (1.1%; 82). Nine of the 19 states where the raccoon-associated variant of the rabies virus has been enzootic reported decreases in the numbers of rabid raccoons during 2001. Among states with extensive wildlife rabies control programs, Ohio reported (other than rabies in bats) 1 case of rabies in a raccoon that was associated with the epizootic of rabies in raccoons and 1 case in a bovid that was infected with a bat variant of the rabies virus, compared with no cases reported in any terrestrial animals during 2000. Texas reported 1 case associated with the dog/coyote variant of the rabies virus (compared with no cases in 2000) and 20 cases associated with the gray fox variant of the virus (a decrease of 50% from reported cases in 2000). Reports of rabid skunks in Massachusetts and Rhode Island, states with enzootic raccoon rabies, exceeded reports of rabid raccoons for the fifth consecutive year. A similar situation may soon exist in the state of Maine (32 rabid skunks and 34 rabid raccoons during 2001). Nationally, the number of rabies cases in skunks during 2001 increased by 2.7% over those reported in 2000. Texas reported the greatest number of rabid skunks ever documented during a single year by any state, as well as the greatest numerical increase in rabid skunks (778 cases in 2001, compared with 550 in 2000; an increase of 228 cases, or 41.5%) and the largest overall state total of rabies cases (1,043) during 2001. Arizona reported the greatest percentage increase in rabid skunks (247.1%), representing an increase from 17 rabid skunks in 2000 to 59 in 2001. Nineteen of these cases were infected with a bat variant of the rabies virus, documenting a spillover event followed by unprecedented detection of temporal enzootic transmission of a bat variant in a terrestrial species. The number of cases of rabies reported in bats during 2001 (1,281 cases) increased 3.3% and surpassed the previous year's record (1,240 cases) as the largest number of reported cases ever recorded for this group of mammals. Cases of rabies reported in dogs (89) and cattle (82) decreased by 21.9 and 1.2%, respectively; these are the lowest numbers reported for rabid cattle and dogs since the dawn of national rabies record keeping (ca 1938). Cases in cats (270) increased by 8.4% over those reported in 2000, whereas rabies among sheep and goats declined 70%, from 10 cases in 2000 to 3 cases (goats only) in 2001. Rabies among horses and mules declined 1.9% (52 cases in 2000 to 51 cases in 2001). Reported cases of rabies in mongooses in Puerto Rico increased 18.6%, compared with the previous year (70 cases in 2001 from 59 cases in 2000), whereas cases of rabies in dogs declined 15.3% (15 to 13). One case of rabies in a human being reported by California during 2001 was the result of infection with a canine variant of the rabies virus acquired outside the United States.

To assess the magnitude of fatal Rocky Mountain spotted fever (RMSF) and to evaluate the completeness of national surveillance for this occurrence from 1983 through 1998, two independent sources of RMSF mortality data were analyzed using a capture-recapture method. Two hundred twenty-four deaths reported through RMSF case report forms (CRFs) were compared with 304 RMSF-associated deaths recorded in the United States multiple cause-of-death (MCD) database. Demographic, geographic, seasonal, and temporal characteristics of decedents were remarkably similar between sources. Median annual deaths ascertained from CRF and MCD data sources were 11 (range = 5-35) and 18 (range = 5-39), respectively. Decedents were matched between sources by year, state, age, sex, race, and month-of-death; 111 deaths were matched to both sources, and percent concordance between CRFs and MCD data during the 16-year study period was 27% (range = 7-45%). An estimated 612 RMSF-associated deaths occurred during the study period (median = 37 per year, range = 16-64), suggesting that approximately 400 fatal cases of RMSF went unreported to national surveillance during the period 1983-1998, for an estimated completeness of CRF reporting of 36%.