West Nile virus infection among the homeless, Houston, Texas (1).Among 397 homeless participants studied, the overall West Nile virus West Nile virus, microorganism and the infection resulting from it, which typically produces no symptoms or a flulike condition. The virus is a flavivirus and is related to a number of viruses that cause encephalitis. (WNV WNV West Nile Virus WNV World Net Visions ) seroprevalence seroprevalence Immunology The proportion of a population that is seropositive–ie, has been exposed to a particular pathogen or immunogen; the seropositivity of a population is calculated as the number of individuals who produce a particular antibody divided was 6.8%. Risk factors for WNV infection included being homeless >1 year, spending >6 hours outside daily, regularly taking mosquito precautions, and current marijuana use. Public health interventions health intervention Health care An activity undertaken to prevent, improve, or stabilize a medical condition need to be directed toward this high-risk population. ********** West Nile virus (WNV) was first identified in Houston in 2002 (1). From 2002 through 2004, 6% of patients hospitalized with WNV infection were homeless (2), which raised concerns that the homeless population might be at increased risk for infection. This study was conducted to determine the seroprevalence of WNV in Houston's homeless population after 2 transmission seasons and to determine risk factors for infection. The Study A cross-sectional survey was conducted by using convenience sampling of homeless shelters, soup kitchens, homeless camps, and mobile outreach organizations. Participants gave consent and were assigned a unique study number to preserve anonymity. An interviewer-administered questionnaire collected information on demographics, social and medical histories, housing status during the 2002 and 2003 WNV transmission seasons, length of time homeless, and outdoor exposures. The study was approved by the University of Texas Health Science Center at Houston Committee for the Protection of Human Subjects (HSC-SPH-03-111). A Mini-Mental State Examination The mini-mental state examination (MMSE) or Folstein test is a brief 30-point questionnaire test that is used to assess cognition. It is commonly used in medicine to screen for dementia. (MMSE MMSE Mini Mental State Examination MMSE Minimum Mean Squared Error MMSE Mini-Mental Status Examination MMSE Multiuse Mission Support Equipment MMSE Multimission Support Equipment MMSE Multi Media Service Environment ) was performed to evaluate the cognitive status of the participant. Participants who scored <75% on the MMSE were considered cognitively impaired, and therefore their interview responses were excluded. As incentive, participants were provided free onsite testing and counseling for HIV HIV (Human Immunodeficiency Virus), either of two closely related retroviruses that invade T-helper lymphocytes and are responsible for AIDS. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of AIDS in the United States. , hepatitis B Hepatitis B Definition Hepatitis B is a potentially serious form of liver inflammation due to infection by the hepatitis B virus (HBV). It occurs in both rapidly developing (acute) and long-lasting (chronic) forms, and is one of the most common chronic , hepatitis C Hepatitis C Definition Hepatitis C is a form of liver inflammation that causes primarily a long-lasting (chronic) disease. Acute (newly developed) hepatitis C is rarely observed as the early disease is generally quite mild. , and WNV infections. Blood samples were collected and later tested for WNV antibodies by immunoglobulin G immunoglobulin G n. Abbr. IgG The most abundant class of antibodies found in blood serum and lymph and active against bacteria, fungi, viruses, and foreign particles. Immunoglobulin G antibodies trigger action of the complement system. (IgG) ELISA ELISA (e-li´sah) Enzyme-Linked Immuno-Sorbent Assay; any enzyme immunoassay using an enzyme-labeled immunoreactant and an immunosorbent. ELISA n. and hemagglutination hemagglutination /he·mag·glu·ti·na·tion/ (he?mah-gloo-ti-na´shun) agglutination of erythrocytes. he·mag·glu·ti·na·tion n. inhibition (HI) test. Samples were considered WNV antibody--positive if both the IgG ELISA IgG ELISA, n.pr a diagnostic test for identifying reactive substances that provoke delayed hypersensitivity of the immune system. A solid-phase immunoassay that uses enzymes to test for IgG subclass reactions. and HI assay gave positive reactions. Data were entered into a Microsoft (Redmond, WA, USA) Access database and analyzed by using Stata 8.0 (Stata Corp., College Station, TX, USA). WNV prevalence and risk of becoming infected were calculated for each variable. Univariate odds ratios (ORs) with p<0.25 were included in a logistic regression In statistics, logistic regression is a regression model for binomially distributed response/dependent variables. It is useful for modeling the probability of an event occurring as a function of other factors. model. A backward stepwise stepwise incremental; additional information is added at each step. stepwise multiple regression used when a large number of possible explanatory variables are available and there is difficulty interpreting the partial regression approach was used to eliminate variables with p>0.10 to determine a final model. Interactions between variables were assessed for significance (p<0.10), and the Hosmer-Lemeshow goodness-of-fit statistic (3) was used to evaluate the fit of the final model. During the spring of 2004, 424 participants were enrolled from 13 sites; 8 were excluded due to low MMSE scores. Of the 416 participants, 397 had complete interviews, adequate blood samples, and were included in the analysis. This sampling represents [approximately equal to] 4% of Houston's estimated 10,000 homeless population (4). Of the 397 participants, 27 were WNV positive (seroprevalence 6.8%; 95% confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. [CI] 4.5-9.7). Men represented 72% of the participants, with 8.4% found to be positive for WNV, compared with 2.7% of women (OR 3.3; 95% CI 0.96-11.0) (Table 1). The study population was 59% black, 30% white, and 11% "other" or not stated; 13% were of Hispanic ethnicity. Mean age was 42 years (range 18-69 years). For both 2002 and 2003 transmission seasons, 278 (70%) participants reported having stable housing, and WNV seroprevalence was 4.7% (95% CI 2.5-7.9) (Table 2). For those who had unstable housing in both 2002 and 2003 (n = 45; 11%), we found a significantly higher WNV seroprevalence of 13.3% (OR 3.1, 95% CI 1.1-8.7). For those who reported being homeless >1 year (n = 73; 18%), seroprevalence for WNV was 16.4% (95% CI 8.8-27.0), with a significantly increased risk for WNV infection when compared with those who did not consider themselves homeless or were homeless <1 month (OR 3.2; 95% CI 1.3-7.7, p = 0.01). When asked about the average length of time spent outdoors during the summer and fall, 38% reported [less than or equal to] 6 hours per day (seroprevalence 2.0%), 38% reported >6-12 hours (seroprevalence 8.0%), and 24% reported >12 hours (seroprevalence 12.5%). There was a positive trend (p value for trend 0.002) between number of hours spent outside and increased risk for WNV infection. Current marijuana use was also associated with WNV infection (OR 2.5; 95% CI 1.0-6.0). Univariate analysis identified the following variables as significantly ([alpha] < 0.05) associated with risk for WNV infection: unstable housing in 2002 and 2003, being homeless >1 year, spending >6 hours outside per day during the summer and fall, and current marijuana use. The final logistic regression model identified the following independent risk factors (p<0.10) for WNV infection: being homeless >1 year (OR 3.8, p = 0.002), spending >6 hours outdoors (OR 4.3, p = 0.02), normally taking mosquito precautions (OR 2.8, p = 0.04), and current marijuana use (OR 2.4, p = 0.07). The Hosmer-Lemeshow goodness-of-fit-test statistic was 12.4 (p>0.19), which suggests that the model is a good fit. When interaction terms were entered into the model, the interaction between marijuana smoking and spending >6 hours outdoors was significant (likelihood ratio p = 0.04) and increased the strength of the association with WNV infection. Conclusions We believe this is the first study to determine the prevalence of WNV in homeless adults and to determine risk factors for becoming infected among this high-risk urban population. Findings from this study will help public health authorities determine appropriate intervention and prevention strategies. We found a seroprevalence of 6.8% in our sample of homeless persons An individual who lacks housing, including one whose primary residence during the night is a supervised public or private facility that provides temporary living accommodations; an individual who is a resident in transitional housing; or an individual who has as a primary residence a , with a seroprevalence of 16.4% in persons reporting being homeless >1 year. Other studies have assessed the prevalence of WNV in general populations in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. (5-10), with estimates of 0% 14%. To our knowledge, this is the first report of WNV seroprevalence in a population with high-risk outdoor exposures. Only 3 studies have evaluated risk factors for infection in the United States and found that increased time outdoors (5,8), inconsistent use of mosquito repellant (5), and age (9) were predictors for infection. In Houston's homeless population, spending >6 hours outside per day during the summer and fall and being homeless > 1 year independently predicted risk for infection. Although being homeless >1 year was highly associated with increased time spent outdoors, this variable also independently predicted infection. This finding is important in a public health context because it highlights a strong potential for further cases of WNV infection in this population. We found that regularly using mosquito precautions was associated with an increased risk for infection, which differs from the findings in New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of (5). This finding was surprising since, in theory, use of mosquito precautions should reduce the risk for WNV infection. However, when asked about the types of mosquito precautions used, many participants reported methods that may be ineffective such as using candles or fire as a deterrent or swatting at mosquitoes. Education regarding appropriate preventive methods would be valuable in this population. In addition, we found that marijuana use predicted WNV infection, which is difficult to explain. To our knowledge, this is the first report of marijuana use being a risk factor for WNV infection. Several explanations are possible, however: 1) this finding was due to chance, 2) persons using marijuana may spend more time outdoors between dusk and dawn when the Culex Culex /Cu·lex/ (ku´leks) a genus of mosquitoes found throughout the world, many species of which are vectors of disease-producing organisms. Cu·lex n. mosquito is most active, 3) the mosquito vector could be attracted to marijuana smoke, or 4) marijuana use could affect cognition, thereby preventing the user from interrupting a mosquito taking a blood meal. The relationship between marijuana use and WNV infection deserves further investigation. For comparison, data on WNV prevalence in a nonhomeless population during the same time period and location would be useful. After the 2003 transmission season, a study at the University of Texas Health Science Center at Houston found a seroprevalence of 4.7% among 274 students, faculty, and staff (K. Murray, unpub, data). This study provides important information on the magnitude and risk factors for WNV infection among homeless persons. Combining education with distribution of effective mosquito prevention aids such as mosquito repellent re·pel·lent adj. Capable of driving off or repelling. n. A substance used to drive off or keep away insects. repellent able to repel or drive off; also, an agent that repels. Refers usually to insect repellent. may help reduce the risk for WNV infection and other mosquitoborne diseases in this high-risk population. Acknowledgments We thank the participants and study sites for their contribution to this study and acknowledge the dedication and hard work of Lu-Yu Hwang, Jim Graham Jim Graham is a politician from Washington, D.C. He is currently a Democratic member of the Council of the District of Columbia, where has served as an elected councilmember for Ward 1 since 1999. Jim Graham is an openly gay, naturalized immigrant from Scotland. , Brian Howard For the American basketball player, see Brian Howard (basketball). For the English football player, see Brian Howard (footballer). Brian Christian de Claiborne Howard , Chidi Okafor, Monica Sierra, Che Ornelas, Timberly Gilford, Don Hall, John Cleveland John Cleveland (June 16, 1613 - April 29, 1658) was an English poet. The son of an usher in a charity school, Cleveland was born in Loughborough, and educated at Hinckley Grammar School and the University of Cambridge, where he became college tutor and lecturer on rhetoric , Ken Meyer Ken Meyer was a former football coach at the high school, collegiate and professional levels. He may be best remembered as the head coach of the National Football League's San Francisco 49ers in 1977. , Philip Lupo, Nancy Taylor, and the University of Texas General Clinical Research Center staff. We also thank Farzad Mostashari and the New York City New York City: see New York, city. New York City City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. Department of Health for sharing the questionnaire from the 1999 WNV serosurvey. This study was funded by a contract with the Texas Department of State Health Services health services Managed care The benefits covered under a health contract , and the University of Texas Health Science Center at Houston, General Clinical Research Center (NIH "Not invented here." See digispeak. NIH - The United States National Institutes of Health. M01-RR 02558). References (1.) Lillibridge KM, Parsons Parsons, city (1990 pop. 11,924), Labette co., SE Kans.; inc. 1871. It is a shipping point for dairy products, grain, and livestock. Manufactures include ammunition, wire and paper products, plastics, and appliances. R, Randle Y, Travassos da Rosa Da Rosa is a Portuguese and Galician family name. Da Rosa is either:
see St. Louis encephalitis. . Am J Trop Med Hyg. 2004;70:676-81. (2.) Murray K, Baraniuk S, Resnick M, Ararat R, Kilborn C, Cain K, et al. Risk factors for encephalitis encephalitis (ĕnsĕf'əlī`təs), general term used to describe a diffuse inflammation of the brain and spinal cord, usually of viral origin, often transmitted by mosquitoes, in contrast to a bacterial infection of the meninges and death from West Nile virus infection. Epidemiol Infect. 2006; 134:1325-32. (3.) Hosmer DW, Lemeshow S. Applied logistic regression. 2nd ed. New York: John Wiley John Wiley may refer to:
(4.) Healthcare for the Homeless--Houston, Inc. Health, Hope and Dignity Program narrative. [cited 2007 Mar 8]. Available from http:// www.homeless-healthcare.org/hhh/overview (5.) Mostashari F, Bunning ML, Kitsutani PT, Singer DA, Nash D, Cooper MJ, et al. Epidemic West Nile West Nile may refer to:
(6.) Busch MP, Wright D J, Custer B, Tobler LH, Stramer SL, Kleinman SH, et al. West Nile virus infections projected from blood donor screening data, United States, 2003. Emerg Infect Dis. 2006; 12:395-402. (7.) Schweitzer BK, Kramer WL, Sambol AR, Meza JL, Hinrichs SH, Iwen PC. Geographic factors contributing to a high seroprevalence of West Nile virus-specific antibodies in humans following an epidemic. Clin Vaccine Immunol. 2006;13:314-8. (8.) Murphy TD, Grandpre J, Novick SL, Seys SA, Harris RW, Musgrave K. West Nile virus infection among health-fair participants, Wyoming 2003: assessment of symptoms and risk factors. Vector Borne Zoonotic Zoonotic A disease which can be spread from animals to humans. Mentioned in: Zoonosis Dis. 2005;5:246-51. (9.) Mandalakas AM, Kippes C, Sedransk J, Kile JR, Garg A, McLeod J, et al. West Nile virus epidemic, northeast Ohio, 2002. Emerg Infect Dis. 2005; 11 : 1774-7. (10.) McCarthy TA, Hadler JL, Julian K, Walsh S J, Biggerstaff B J, Hinten SR, et al. West Nile virus serosurvey and assessment of personal prevention efforts in an area with intense epizootic ep·i·zo·ot·ic adj. Affecting a large number of animals at the same time within a particular region or geographic area. Used of a disease. ep activity: Connecticut, 2000. Ann N Y Acad Sci. 2001;951:307-16. Tamra E. Meyer, * Lara M. Bull, * Kelly Cain Holmes, * Rhia F. Pascua, * Amelia Travassos da Rosa, ([dagger]) Christian R. Gutierrez, * Tracie Corbin, * Jennifer L. Woodward, * Jeffrey P. Taylor, ([double dagger double dagger n. A reference mark (  ) used in printing and writing. Also called diesis.Noun 1. ]) Robert B. Tesh, ([dagger]) and Kristy O. Murray * * University of Texas Health Science Center at Houston, Houston, Texas “Houston” redirects here. For other uses, see Houston (disambiguation). Houston (pronounced /'hjuːstən/) is the largest city in the state of Texas and the , USA; ([dagger]) University of Texas Medical Branch "UTMB" redirects here. For other system schools, see University of Texas System. The University of Texas Medical Branch (UTMB) is a component of the University of Texas System located in Galveston, Texas, about 50 miles (80 km) southeast of downtown Houston. , Galveston, Texas
(1) This research was presented in part at the International Conference on Emerging Infectious Diseases The ICEID or International Conference on Emerging Infectious Diseases is a conference for public health professionals on the subject of emerging infectious diseases. , Atlanta, Georgia, USA, on March 21, 2006. Address for correspondence: Kristy O. Murray, University of Texas Health Science Center at Houston, School of Public Health, 1200 Herman Pressler, Suite E-707, Houston, TX 77030, USA; email: kristy.o.murray@ uth.tmc.edu Ms Meyer is a doctoral candidate in epidemiology at the University of Texas Health Science Center at Houston, School of Public Health. Her current research involves genetic risk factors for prostate cancer prostate cancer, cancer originating in the prostate gland. Prostate cancer is the leading malignancy in men in the United States and is second only to lung cancer as a cause of cancer death in men. .
Table 1. Participant demographics and WNV prevalence
from the 2004 Houston Homeless Seroprevalence Study *
All WNV prevalence
participants,
Demographic characteristics n = 397 (%) No. (%) 95% CI
Sex
Female 110 (28) 3 (2.7) 0.6-7.8
Male 287 (72) 24 (8.4) 5.4-12.2
Age, y
18-34 97 (24) 2 (2.1) 0.3-7.3
35-49 204 (51) 17 (8.3) 4.9-13.0
[greater than or equal to] 50 95 (24) 8 (8.4) 3.7-15.9
Unknown 1 (0.3) 0 --
Race
White 120 (30) 8 (6.7) 2.9-12.7
Black 233 (59) 18 (7.7) 4.6-11.9
Other/unknown 44 (11) 1 (2.3) 0.06-12.0
Ethnicity
Hispanic 52 (13) 2 (3.9) 0.5-13.2
Non-Hispanic 343 (86) 24 (7.0) 4.5-10.2
No response 2 (0.5) 1 (50.0) 1.3-98.7
Risk for WNV
infection,
Demographic characteristics OR (95% CI)
Sex
Female Reference
Male 3.3 (0.96-11.0)
Age, y
18-34 Reference
35-49 4.3 (0.98-19.1)
[greater than or equal to] 50 4.4 (0.9-21.1)
Unknown --
Race
White Reference
Black 1.2 (0.5-2.8)
Other/unknown 0.3 (0.04-2.7)
Ethnicity
Hispanic Reference
Non-Hispanic 1.9 (0.4-8.2)
No response --
* WNV, West Nile virus; OR, odds ratio; CI, confidence interval.
Table 2. Self-reported social histories and prevalence of WNV
infection from the 2004 Houston Homeless Seroprevalence Study *
All WNV prevalence
participants,
Participant characteristics n = 397 (%) No. (%) 95% CI
Housing status ([dagger])
Stable housing, 278 (70) 13 (4.7) 2.5-7.9
2002 and 2003
Unstable housing, 69 (17) 7 (10.1) 4.2-19.8
2002 or 2003
Unstable housing, 45 (11) 6 (13.3) 5.1-26.8
2002 and 2003
Unknown 5 (1) 1 (20.0) 0.5-71.6
Homelessness status
Does not consider himself 111 (28) 8 (7.2) 3.2-13.7
or herself homeless
Lives mostly on the streets 50 (13) 6 (12.0) 4.5-24.3
Lives in temporary shelter 125 (31) 10 (8.0) 3.9-14.2
Lives temporarily with 64 (16) 1 (1.6) 0.04-8.4
friends/family
Other 47 (12) 2 (4.3) 0.5-14.5
Length of time homeless
Does not consider himself 171 (43) 10 (5.9) 2.8-10.5
or herself homeless or
homeless <1 mo
1 mo-1 y 153 (39) 5 (3.3) 1.1-7.5
>1 y 73 (18) 12 (16.4) 8.8-27.0
Time spent outdoors on
average each day during
summer and fall ([section])
[less than or equal to] 6h 150 (38) 3 (2.0) 0.4-5.7
6-12 h 150 (38) 12 (8.0) 4.2-13.6
>12 h 96 (24) 12 (12.5) 6.6-20.8
Unknown 1 (0.3) 0 (0) --
Substance use (#)
Current tobacco use 273 (69) 20 (7.3) 4.5-11.1
>15 drinks containing 70 (18) 3 (4.3) 0.9-12.0
alcohol/wk
Ever used street drugs 281 (71) 19 (6.8) 4.1-10.4
Ever used needles to inject 89 (22) 6 (6.7) 2.5-14.1
street drugs
Current drug use (within 108 (27) 11 (10.2) 5.2-17.5
past 6 mo)
Street drugs used in past
6 mo **
CNS stimulants (crack/ 84 (21) 5 (6.0) 2.0-13.3
cocaine/amphetamines)
Heroin/opiates 4 (1) 0 (0) --
Marijuana 61 (15) 8 (13.1) 5.8-24.2
Risk for WNV infection,
Participant characteristics OR (95% CI)
Housing status ([dagger])
Stable housing, Reference
2002 and 2003
Unstable housing, 2.3 (0.9-6.0)
2002 or 2003
Unstable housing, 3.1 (1.1-8.7) ([double dagger])
2002 and 2003
Unknown --
Homelessness status
Does not consider himself Reference
or herself homeless
Lives mostly on the streets 1.8 (0.6-5.4)
Lives in temporary shelter 1.1 (0.4-2.9)
Lives temporarily with 0.2 (0.02-1.7)
friends/family
Other 0.6 (0.1-2.8)
Length of time homeless
Does not consider himself Reference
or herself homeless or
homeless <1 mo
1 mo-1 y 0.5 (0.2-1.6)
>1 y 3.2 (1.3-7.7) ([double dagger])
Time spent outdoors on
average each day during
summer and fall ([section])
[less than or equal to] 6h Reference
6-12 h 4.3 (1.2-15.4) ([pragraph])
>12 h 7.0 (1.9-25.5) ([double dagger])
Unknown --
Substance use (#)
Current tobacco use 1.3 (0.5-3.2)
>15 drinks containing 0.6 (0.2-1.9)
alcohol/wk
Ever used street drugs 1.0 (0.4-2.3)
Ever used needles to inject 1.0 (0.4-2.5)
street drugs
Current drug use (within 1.9 (0.9-4.3)
past 6 mo)
Street drugs used in past
6 mo **
CNS stimulants (crack/ 0.8 (0.3-2.3)
cocaine/amphetamines)
Heroin/opiates --
Marijuana 2.5 (1.0-6.0) ([paragraph])
* WNV, West Nile virus; OR, odds ratio; CI, confidence
interval; CNS, central nervous system.
([dagger]) p value for trend = 0.02.
([double dagger]) Significant at [alpha] = 0.01.
([section]) p value for trend = 0.002.
([paragraph]) Significant at a = 0.05.
(#) Alcohol and current drug use will most likely be
underestimated because shelters did not allow use of
these substances.
** Not mutually exclusive, hence univariate analysis
compared specific drug use with no use of that drug.
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