West nile virus epidemiology and demographics: Difference between revisions

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{{West nile virus}}
{{West nile virus}}
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{{CMG}}; {{AE}} {{JS}}; {{MJM}}
 
==Overview==
==Overview==
WNV is considered a worldwide infective agent. Since most cases are [[asymptomatic]] and self-limited, the true [[incidence]] and [[prevalence]] of West Nile virus fever are often underestimated. Between the years 1999 and 2013, a total of 39557 cases were reported by the [[CDC]] in USA alone. The 2002 outbreak in USA marks the WNV outbreak with the most recorded rates of neuroinvasive disease. Nonetheless, only 1/140 to 1/256 cases of West Nile fever are complicated by [[encephalitis]] or [[meningitis]]. WNV [[infection]] occurs predominantly during the end of summer and beginning of fall. Females are more likely to develop WNV infection. The prevalence of the disease is not affected by ethnicity or age, but elderly patients are more likely to experience a complicated clinical course.


==Epidemiology==
==Incidence and Prevalence==
 
WNV is widely distributed across Australia, Middle East, Western Russia, Southwestern Asia, Africa and Southern Europe. A series of outbreaks in the Mediterranean basin between 1950 and 1960 and in Europe and Africa between 1970 and 1980, marking a continuously waxing and waning incidence during the second half of the 20th century.<ref name="MayDavis2010">{{cite journal|last1=May|first1=F. J.|last2=Davis|first2=C. T.|last3=Tesh|first3=R. B.|last4=Barrett|first4=A. D. T.|title=Phylogeography of West Nile Virus: from the Cradle of Evolution in Africa to Eurasia, Australia, and the Americas|journal=Journal of Virology|volume=85|issue=6|year=2010|pages=2964–2974|issn=0022-538X|doi=10.1128/JVI.01963-10}}</ref> In America, the virus was first isolated in 1999 in New York City. The WNV disseminated rapidly across the American continent to the West coast in just 4 years and to Argentina in 6 years.<ref name="pmid20360671">{{cite journal| author=Lindsey NP, Staples JE, Lehman JA, Fischer M, Centers for Disease Control and Prevention (CDC)| title=Surveillance for human West Nile virus disease - United States, 1999-2008. | journal=MMWR Surveill Summ | year= 2010 | volume= 59 | issue= 2 | pages= 1-17 | pmid=20360671 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20360671  }} </ref><ref name="pmid19145778">{{cite journal| author=Petersen LR, Hayes EB| title=West Nile virus in the Americas. | journal=Med Clin North Am | year= 2008 | volume= 92 | issue= 6 | pages= 1307-22, ix | pmid=19145778 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19145778  }} </ref> The 2002 outbreak in USA marked the highest rate of neuroinvasive disease of a single WNV outbreak. The total number of infected patients reached 4156, with 2942 (71%) of those suffering severe neuroinvasive disease.<ref name="pmid15018774">{{cite journal| author=O'Leary DR, Marfin AA, Montgomery SP, Kipp AM, Lehman JA, Biggerstaff BJ et al.| title=The epidemic of West Nile virus in the United States, 2002. | journal=Vector Borne Zoonotic Dis | year= 2004 | volume= 4 | issue= 1 | pages= 61-70 | pmid=15018774 | doi=10.1089/153036604773083004 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15018774  }} </ref>
The human case-fatality rate in the U.S. has been 7% overall, and among patients with neuroinvasive WNV disease, 10%.
 
In general, the WNV transmission season in the U.S. is longer than that for other domestic arboviruses and requires longer periods of ecologic and human surveillance.


''1. Northeastern and Midwestern U.S.''
Most patients with WNV infection are [[asymptomatic]]. Accordingly, West Nile fever is considered to be underreported, either because infected patients do not seek medical attention or because they are not tested for the virus.<ref name="pmid19145778">{{cite journal| author=Petersen LR, Hayes EB| title=West Nile virus in the Americas. | journal=Med Clin North Am | year= 2008 | volume= 92 | issue= 6 | pages= 1307-22, ix | pmid=19145778 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19145778  }} </ref> Between 1999 and 2013, a total 39557 probable and confirmed cases of West Nile fever were reported to the [[CDC]] from across the US.<ref name="pmid23860989">{{cite journal| author=Petersen LR, Brault AC, Nasci RS| title=West Nile virus: review of the literature. | journal=JAMA | year= 2013 | volume= 310 | issue= 3 | pages= 308-15 | pmid=23860989 | doi=10.1001/jama.2013.8042 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23860989  }} </ref><ref name="pmid20360671">{{cite journal| author=Lindsey NP, Staples JE, Lehman JA, Fischer M, Centers for Disease Control and Prevention (CDC)| title=Surveillance for human West Nile virus disease - United States, 1999-2008. | journal=MMWR Surveill Summ | year= 2010 | volume= 59 | issue= 2 | pages= 1-17 | pmid=20360671 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20360671  }} </ref> The [[outbreak]] of 2012, in which 2873 cases of neuroinvasive disease were reported, occurred during a period of increased mosquito [[infection]] rate. A possible explanation for this was the severe precipitation felt during the previous winter.<ref name="ChungBuseman2013">{{cite journal|last1=Chung|first1=Wendy M.|last2=Buseman|first2=Christen M.|last3=Joyner|first3=Sibeso N.|last4=Hughes|first4=Sonya M.|last5=Fomby|first5=Thomas B.|last6=Luby|first6=James P.|last7=Haley|first7=Robert W.|title=The 2012 West Nile Encephalitis Epidemic in Dallas, Texas|journal=JAMA|volume=310|issue=3|year=2013|pages=297|issn=0098-7484|doi=10.1001/jama.2013.8267}}</ref><ref name="GoodmanLivingston2012">{{cite journal|last1=Goodman|first1=Denise M.|last2=Livingston|first2=Edward H.|title=West Nile Virus|journal=JAMA|volume=308|issue=10|year=2012|pages=1052|issn=0098-7484|doi=10.1001/2012.jama.11678}}</ref>


In the northeastern states in 2001-2002, human illness onset occurred as early as early July and as late as mid-November. During these same years, avian cases occurred as early as the first week of April and as late as the second week of December. Active ecological surveillance and enhanced passive surveillance for human cases should begin in early spring and continue through the fall until mosquito activity ceases because of cold weather. Surveillance in urban and suburban areas should be
[[Image:WNV cumulative human disease cases.png|thumb|center|500 px|USA cumulative human disease cases of WNV in 2014. ''Data as of September 2014''<SMALL><SMALL>''[http://www.cdc.gov  - Center for Disease Control and Prevention(CDC)]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url =  http://www.cdc.gov}}</ref></SMALL></SMALL>]]
emphasized.


''2. Southern U.S.''
[[Image:WNV Cumulative 2014 Data.png|thumb|center|500 px| WNV Cumulative 2014 Data. ''Data as of September 2014''<SMALL><SMALL>''[http://www.cdc.gov  - Center for Disease Control and Prevention(CDC)]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url =  http://www.cdc.gov}}</ref></SMALL></SMALL>]]


In 2001-2002, WNV circulated throughout the year, especially in the Gulf states. Although, in 2001-2002, human illness onset was reported as early as mid-May and June and as late as mid-December, equine and avian infections were reported in all 22 months of the year. Active ecologic surveillance and enhanced passive surveillance for human cases should be conducted year round in these areas.
==Age==
*The prevalence of WNV does not change with age.
*Elderly patients have a higher risk of developing severe forms of the disease.<ref name="MayDavis2010">{{cite journal|last1=May|first1=F. J.|last2=Davis|first2=C. T.|last3=Tesh|first3=R. B.|last4=Barrett|first4=A. D. T.|title=Phylogeography of West Nile Virus: from the Cradle of Evolution in Africa to Eurasia, Australia, and the Americas|journal=Journal of Virology|volume=85|issue=6|year=2010|pages=2964–2974|issn=0022-538X|doi=10.1128/JVI.01963-10}}</ref><ref name="pmid20874087">{{cite journal| author=Zou S, Foster GA, Dodd RY, Petersen LR, Stramer SL| title=West Nile fever characteristics among viremic persons identified through blood donor screening. | journal=J Infect Dis | year= 2010 | volume= 202 | issue= 9 | pages= 1354-61 | pmid=20874087 | doi=10.1086/656602 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20874087  }} </ref>


''3. Western U.S.''
==Gender==
WNV is more prevalent in women.<ref name="MayDavis2010">{{cite journal|last1=May|first1=F. J.|last2=Davis|first2=C. T.|last3=Tesh|first3=R. B.|last4=Barrett|first4=A. D. T.|title=Phylogeography of West Nile Virus: from the Cradle of Evolution in Africa to Eurasia, Australia, and the Americas|journal=Journal of Virology|volume=85|issue=6|year=2010|pages=2964–2974|issn=0022-538X|doi=10.1128/JVI.01963-10}}</ref><ref name="pmid20874087">{{cite journal| author=Zou S, Foster GA, Dodd RY, Petersen LR, Stramer SL| title=West Nile fever characteristics among viremic persons identified through blood donor screening. | journal=J Infect Dis | year= 2010 | volume= 202 | issue= 9 | pages= 1354-61 | pmid=20874087 | doi=10.1086/656602 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20874087  }} </ref>


In 2002, WNV activity was first reported among humans and animals in Rocky Mountain states and among animals in Pacific coast states. These events occurred relatively late in the year (mid-August). Predicting the temporal characteristics of future WNV
==Race==
transmission seasons based on these limited reports is not possible. Despite this limitation, active ecological surveillance and enhanced passive surveillance for human cases beginning in early spring and continuing through the fall until mosquito activity ceases because of cold weather should be encouraged.
The prevalence of WNV does not vary by race or ethnicity.


''4. Other Areas of the Western Hemisphere''
==Season==
Infection with WNV commonly occurs during warmer seasons, such as the period between late summer and beginning of fall.<ref name="pmid23860989">{{cite journal| author=Petersen LR, Brault AC, Nasci RS| title=West Nile virus: review of the literature. | journal=JAMA | year= 2013 | volume= 310 | issue= 3 | pages= 308-15 | pmid=23860989 | doi=10.1001/jama.2013.8042 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23860989  }} </ref>


In 2002, Canada experienced a WNV epidemic in Ontario and Quebec provinces and an equine/avian epizootic that extended from the maritime provinces to Saskatchewan. Recent serologic evidence supports the conclusion that WNV has now reached Central
==Geographical Distribution==
America. Further spread to South America by migratory birds seems inevitable, if this has not already occurred. Development of surveillance systems capable of detecting WNV activity should be encouraged in the Caribbean and Central and South America.
WNV is considered a global virus. Outbreaks of the virus have been documented since its initial isolation in 1937 in approximately all regions of the world.
WNV surveillance should be integrated with dengue surveillance in these areas, and with yellow fever surveillance in areas where urban or peri-urban transmission of this virus occurs.


==Demographics==
===US disease sases by state - 2014===
[[Image:Map WNV 807 07 a.jpg|frame|left|2007 West Nile Virus Activity in the United States; reported to CDC as of August 7, 2007]]
[[Image:West Nile Virus Disease Cases.png|thumb|center|1000 px| US West Nile Virus Disease Cases<SMALL><SMALL>''[http://www.cdc.gov  - Center for Disease Control and Prevention( CDC)]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url =  http://www.cdc.gov}}</ref></SMALL></SMALL>]]


''Map shows the distribution of avian, animal, or mosquito infection occurring during 2007 with number of human cases if any, by state. If West Nile virus infection is reported to CDC from any area of a state, that entire state is shaded.''
===West Nile virus by state - 2014===
[[Image:West Nile Virus Activity by State.png|thumb|center|1000 px| US West Nile Virus Disease Cases<SMALL><SMALL>''[http://www.cdc.gov  - Center for Disease Control and Prevention (CDC)]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url =  http://www.cdc.gov}}</ref></SMALL></SMALL>]]


Data table:
==Neuroinvasive disease incidence by state - 2014=
[[Image:West Nile Virus Neuroinvasive Disease Incidence by State.png|center|500px|thumb|Average annual incidence of West Nile Virus neuroinvasive disease 1999-2012<SMALL><SMALL>''[http://www.cdc.gov  - Center for Disease Control and Prevention (CDC)]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url =  http://www.cdc.gov}}</ref></SMALL></SMALL>]]


Avian, animal or mosquito WNV infections have been reported to CDC ArboNET from the following states in 2007:  Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Kansas, Louisiana, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Puerto Rico, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin, and Wyoming.


Human cases have been reported in Alabama, Arizona, Arkansas, California, Colorado, Georgia, Idaho, Illinois, Iowa, Kansas, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, North Dakota, Ohio, Pennsylvania, South Dakota, Texas, Utah, Virginia, and Wyoming.[http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-guidelines-aug-2003.pdf]
===Neuroinvasive Disease Archives===
[http://www.cdc.gov/ncidod/dvbid/westnile/Mapsactivity/surv&control07Maps.htm]
<gallery>
 
Image:WNV I1.jpg
West Nile virus has been described in [[Africa]], [[Europe]], the [[Middle East]], west and central [[Asia]], [[Oceania]] (subtype Kunjin), and most recently, North America.
Image:WNV I2.jpg
 
Image:WNV I3.jpg
Recent outbreaks of West Nile virus encephalitis in humans have occurred in [[Algeria]] ([[1994]]), [[Romania]] ([[1996]] to 1997), the [[Czech Republic]] (1997), [[Democratic Republic of the Congo|Congo]] ([[1998]]), [[Russia]] (1999), the United States (1999 to 2003), Canada (1999&ndash;2003), and [[Israel]] ([[2000]]).
Image:WNV I4.jpg
 
Image:WNV I5.jpg
Epizootics of disease in horses occurred in [[Morocco]] (1996), [[Italy]] (1998), the United States (1999 to 2001), and [[France]] (2000). In 2003, West Nile virus spread among horses in Mexico.
Image:WNV I6.jpg
Image:WNV I7.jpg
Image:WNV I8.jpg
Image:WNV I9.jpg
Image:WNV I10.jpg
Image:WNV I11.jpg
</gallery>


==References==
==References==
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[[Category:Disease]]
[[Category:Disease]]
[[Category:Infectious disease]]
 
[[Category:Neurology]]
[[Category:Neurology]]

Latest revision as of 19:11, 18 September 2017

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]; Michael Maddaleni, B.S.

Overview

WNV is considered a worldwide infective agent. Since most cases are asymptomatic and self-limited, the true incidence and prevalence of West Nile virus fever are often underestimated. Between the years 1999 and 2013, a total of 39557 cases were reported by the CDC in USA alone. The 2002 outbreak in USA marks the WNV outbreak with the most recorded rates of neuroinvasive disease. Nonetheless, only 1/140 to 1/256 cases of West Nile fever are complicated by encephalitis or meningitis. WNV infection occurs predominantly during the end of summer and beginning of fall. Females are more likely to develop WNV infection. The prevalence of the disease is not affected by ethnicity or age, but elderly patients are more likely to experience a complicated clinical course.

Incidence and Prevalence

WNV is widely distributed across Australia, Middle East, Western Russia, Southwestern Asia, Africa and Southern Europe. A series of outbreaks in the Mediterranean basin between 1950 and 1960 and in Europe and Africa between 1970 and 1980, marking a continuously waxing and waning incidence during the second half of the 20th century.[1] In America, the virus was first isolated in 1999 in New York City. The WNV disseminated rapidly across the American continent to the West coast in just 4 years and to Argentina in 6 years.[2][3] The 2002 outbreak in USA marked the highest rate of neuroinvasive disease of a single WNV outbreak. The total number of infected patients reached 4156, with 2942 (71%) of those suffering severe neuroinvasive disease.[4]

Most patients with WNV infection are asymptomatic. Accordingly, West Nile fever is considered to be underreported, either because infected patients do not seek medical attention or because they are not tested for the virus.[3] Between 1999 and 2013, a total 39557 probable and confirmed cases of West Nile fever were reported to the CDC from across the US.[5][2] The outbreak of 2012, in which 2873 cases of neuroinvasive disease were reported, occurred during a period of increased mosquito infection rate. A possible explanation for this was the severe precipitation felt during the previous winter.[6][7]

USA cumulative human disease cases of WNV in 2014. Data as of September 2014- Center for Disease Control and Prevention(CDC)[8]
WNV Cumulative 2014 Data. Data as of September 2014- Center for Disease Control and Prevention(CDC)[8]

Age

  • The prevalence of WNV does not change with age.
  • Elderly patients have a higher risk of developing severe forms of the disease.[1][9]

Gender

WNV is more prevalent in women.[1][9]

Race

The prevalence of WNV does not vary by race or ethnicity.

Season

Infection with WNV commonly occurs during warmer seasons, such as the period between late summer and beginning of fall.[5]

Geographical Distribution

WNV is considered a global virus. Outbreaks of the virus have been documented since its initial isolation in 1937 in approximately all regions of the world.

US disease sases by state - 2014

US West Nile Virus Disease Cases- Center for Disease Control and Prevention( CDC)[8]

West Nile virus by state - 2014

US West Nile Virus Disease Cases- Center for Disease Control and Prevention (CDC)[8]

=Neuroinvasive disease incidence by state - 2014

Average annual incidence of West Nile Virus neuroinvasive disease 1999-2012- Center for Disease Control and Prevention (CDC)[8]


Neuroinvasive Disease Archives

References

  1. ↑ 1.0 1.1 1.2 May, F. J.; Davis, C. T.; Tesh, R. B.; Barrett, A. D. T. (2010). "Phylogeography of West Nile Virus: from the Cradle of Evolution in Africa to Eurasia, Australia, and the Americas". Journal of Virology. 85 (6): 2964–2974. doi:10.1128/JVI.01963-10. ISSN 0022-538X.
  2. ↑ 2.0 2.1 Lindsey NP, Staples JE, Lehman JA, Fischer M, Centers for Disease Control and Prevention (CDC) (2010). "Surveillance for human West Nile virus disease - United States, 1999-2008". MMWR Surveill Summ. 59 (2): 1–17. PMID 20360671.
  3. ↑ 3.0 3.1 Petersen LR, Hayes EB (2008). "West Nile virus in the Americas". Med Clin North Am. 92 (6): 1307–22, ix. PMID 19145778.
  4. ↑ O'Leary DR, Marfin AA, Montgomery SP, Kipp AM, Lehman JA, Biggerstaff BJ; et al. (2004). "The epidemic of West Nile virus in the United States, 2002". Vector Borne Zoonotic Dis. 4 (1): 61–70. doi:10.1089/153036604773083004. PMID 15018774.
  5. ↑ 5.0 5.1 Petersen LR, Brault AC, Nasci RS (2013). "West Nile virus: review of the literature". JAMA. 310 (3): 308–15. doi:10.1001/jama.2013.8042. PMID 23860989.
  6. ↑ Chung, Wendy M.; Buseman, Christen M.; Joyner, Sibeso N.; Hughes, Sonya M.; Fomby, Thomas B.; Luby, James P.; Haley, Robert W. (2013). "The 2012 West Nile Encephalitis Epidemic in Dallas, Texas". JAMA. 310 (3): 297. doi:10.1001/jama.2013.8267. ISSN 0098-7484.
  7. ↑ Goodman, Denise M.; Livingston, Edward H. (2012). "West Nile Virus". JAMA. 308 (10): 1052. doi:10.1001/2012.jama.11678. ISSN 0098-7484.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 "Center for Disease Control and Prevention (CDC)".
  9. ↑ 9.0 9.1 Zou S, Foster GA, Dodd RY, Petersen LR, Stramer SL (2010). "West Nile fever characteristics among viremic persons identified through blood donor screening". J Infect Dis. 202 (9): 1354–61. doi:10.1086/656602. PMID 20874087.


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