CDC Publication: West Nile Recovery Can Take More Than a Year For Some, Esp. Those Over 65Return To Front Page
(August 20, 2004) -- The Centers for Disease Control & Prevention (CDC) publication Emerging Infectious Diseases reports that individuals with clinical infection [i.e. with symptoms] of the mosquito-borne West Nile Virus showed a significant number suffered a "protracted convalescent period with long-term physical, cognitive, and functional impairments lasting > [greater than] 18 months after acute illness."
The article, Long-Term Prognosis for Clinical West Nile Virus Infection, authored by doctors with the New York City Dept. of Public Health in cooperation with the CDC, indicated that for some people, physical, functional, and cognitive symptoms, including muscle weakness, loss of concentration, confusion, and lightheadedness for persisted after a year, with only 37% achieving a full recovery by one year...and those over age 65 the worst affected.
The article notes that "[r]elatively little is known about the long-term prognosis for patients with clinical West Nile virus (WNV) infection" and younger age at infection was the only significant predictor of recovery, stating in part:
Our study documents that, in addition to causing severe acute illness, WNV meningitis or encephalitis likely results in a prolonged recuperation and rehabilitation period, especially in older persons. As WNV continues to establish itself as a national public health concern, these findings reinforce the need for local governments in affected areas to institute widespread public health measures to safeguard against WNV transmission and for persons -- especially those age 65 and over -- to take precautions to avoid exposure to mosquitoes and reduce mosquito breeding sites on their properties.
LBReport.com quotes an extended portion of the text below...and also posts a link to the full article below:
We report that WNV infection can result in a protracted convalescent period with long-term physical, cognitive, and functional impairments lasting >18 months after acute illness. Approximately 40% of patients hospitalized in 1999 did not return to their own homes immediately after discharge, and physical therapy was required by 47% of patients after hospitalization. Comparing the prevalence of symptoms before illness with that at 12 months after WNV illness onset, physical, functional, and cognitive symptoms persisted. We estimate that 37% achieved full recovery by 12 months. Younger age (<65 years) was the only significant predictor of achieving a full recovery.
...Regardless of acute clinical symptoms, WNV case-patients in this study continued to report difficulty walking, muscle weakness, fatigue, and insomnia, with >40% reporting a combination of these difficulties, and 30% continued to report persistence of memory loss, confusion, depression, and irritability at 18 months after acute illness. Eighteen months after illness, 30% of case-patients reported needing assistance with activities of daily living, mostly those requiring increased strength. Although average functional ability from 6 months to 1 year post-onset improved significantly, functional ability reached a plateau and did not improve further during the 12- to 18-month period.
Our results suggest that WNV has more severe long-term sequelae in older persons than in younger persons. These sequelae may be attributable to the severity of the patients' WNV infection, to the more general effects of serious illness and hospitalization, or to the aging process itself; regardless, WNV causes severe neurologic illness and might be associated with lasting sequelae in persons >65 years.
The presence of underlying disease at the time of onset of illness was not significantly associated with recovery at 12 months (RR = 1.4, 95% CI 0.58–3.3), even after adjusting for age (adjusted RR = 1.3, 95% CI 0.70–2.5). However, the lack of significance of this association could be a result of the small number of patients in our study or misclassification.
Several aspects of our investigation might limit the generalizability of these findings. Although participation was high, our estimates may be imprecise because of the small sample size. Furthermore, the ages of the study participants span a wide range (16 - 90 years), making adequate adjusting for age difficult...Subjective accounts provided by persons who are cognitively impaired might overattribute or underattribute certain dysfunctions to their WNV illness, and recall bias might have caused case-patients to selectively suppress or exaggerate information about their health status, either current or past.
...As WNV continues to affect older age groups, further research should consider ways to control for declines in functioning associated with the aging process and to obtain objective data regarding baseline status. Finally, future studies should try to assess the baseline health status of WNV patients closer to the time of onset to reduce the impact of recall bias on long-term measures of recovery.
Our study documents that, in addition to causing severe acute illness, WNV meningitis or encephalitis likely results in a prolonged recuperation and rehabilitation period, especially in older persons. As WNV continues to establish itself as a national public health concern, these findings reinforce the need for local governments in affected areas to institute widespread public health measures to safeguard against WNV transmission and for persons -- especially those age 65 and over -- to take precautions to avoid exposure to mosquitoes and reduce mosquito breeding sites on their properties. More studies are needed to document the long-term sequelae of this increasingly common infection.
West Nile Virus produces no clinical symptoms in roughly 80% of those bitten by infected mosquitoes, but causes flu-like symptoms in about 20%. It can lead to encephalitis (brain swelling) or meningitis in about 1 in 150 people bitten by WNV infected mosquitoes. There is no cure, only supportive therapies which include hospitalization in serious cases.
To view the entire article, click Long-Term Prognosis for Clinical West Nile Virus Infection, CDC Publication Emerging Infectious Diseases.
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