West Nile virus serosurvey and assessment of personal prevention efforts in an area with intense epizootic activity: Connecticut, 2000

Do we protect ourselves against West Nile Virus? A systematic review on knowledge, attitudes, and practices and their determinants

BACKGROUND

West Nile virus (WNV) is a mosquito-borne flavivirus. In humans, 80% of infections are asymptomatic, while approximately 20% experience influenza-like symptoms. Fewer than 1% develop the neuroinvasive form which can lead to encephalitis, meningitis, acute flaccid paralysis, and even death. The global spread of the virus to areas where it was not previously present has become a growing concern. Since the 2000 s, there have been numerous outbreaks affecting local and travelling populations worldwide. Given the lack of a vaccine, preventative measures are primarily focused on surveillance, vector control, and the use of personal protective behaviours (PPBs). The importance of PPBs is central to public health recommendations. However, translating these messages into coherent action by the public can prove challenging, as the uptake of such measures is inevitably influenced by socio-economic factors, awareness, knowledge, and risk perception.

METHODS

A PRISMA-based systematic research was conducted on EMBASE, PubMed/MEDLINE, and Web of Science databases. PROSPERO registration number CRD42023459714. Quality of studies included in the final stage was evaluated using the Critical Appraisal Checklist for Cross-Sectional Study (CEBMa).

RESULTS

2963 articles were screened, and 17 studies were included in the final round. Out of these, six were deemed of high quality, ten were of medium quality, and one was of low quality. In almost all studies considered, both awareness and knowledge of WNV transmission were above 90%, while concern about WNV ranged from 50% to 80%. Concern about the safety of repellents, either with or without DEET, ranged from 27% to 70%. The percentage of people actually using repellents ranged from 30% to 75%, with the lowest usage reported among individuals over 60 years old (29%) and pregnant women (33%), and the highest among students aged 9-11 (75%). Concern for West Nile Virus (WNV) was consistently linked to an increase in taking preventative measures, including the use of repellents, by two to four times across studies. The school-based intervention was effective in increasing the practice of removing standing water (AOR=4.6; 2.7-8.0) and wearing long clothing (AOR=2.4; 95%CI: 1.3-4.3), but did not have a significant impact on the use of repellents.

CONCLUSIONS

The present systematic review provides an overview of the knowledge, attitudes, and practices (KAP) of WNV and their determinants. While concern about West Nile Virus (WNV) and its effects can be a significant motivator, it is important to promote evidence-based personal protective behaviours (PPBs) to counter unwarranted fears. For example, the use of repellents among the most vulnerable age groups. Given the geographical expansion of WNV, it is necessary to target the entire population preventively, including those who are difficult to reach and areas not yet endemic. The findings of this investigation could have significant implications for public health and support well-informed and effective communication strategies and interventions.

Effects of climate change and human activities on vector-borne diseases

Vector-borne diseases are transmitted by haematophagous arthropods (for example, mosquitoes, ticks and sandflies) to humans and wild and domestic animals, with the largest burden on global public health disproportionately affecting people in tropical and subtropical areas. Because vectors are ectothermic, climate and weather alterations (for example, temperature, rainfall and humidity) can affect their reproduction, survival, geographic distribution and, consequently, ability to transmit pathogens. However, the effects of climate change on vector-borne diseases can be multifaceted and complex, sometimes with ambiguous consequences. In this Review, we discuss the potential effects of climate change, weather and other anthropogenic factors, including land use, human mobility and behaviour, as possible contributors to the redistribution of vectors and spread of vector-borne diseases worldwide.

Cost effectiveness and impact of a targeted age- and incidence-based West Nile virus vaccine strategy

BACKGROUND

West Nile virus (WNV) is the leading cause of arboviral disease in the United States and is associated with significant morbidity and mortality. A previous analysis found that a vaccination program targeting persons aged ≥60 years was more cost effective than universal vaccination, but costs remained high.

METHODS

We used a mathematical Markov model to evaluate cost-effectiveness of an age- and incidence-based WNV vaccination program. We grouped states and large counties (≥100,000 persons aged ≥60 years) by median annual WNV incidence rates from 2004 to 2017 for persons aged ≥60 years. We defined WNV incidence thresholds, in increments of 0.5 cases per 100,000 persons ≥60 years. We calculated potential cost per WNV vaccine-prevented case and per quality adjusted life years (QALYs) saved.

RESULTS

Vaccinating persons aged ≥60 years in states with an annual incidence of WNV neuroinvasive disease of ≥0.5 per 100,000 resulted in approximately half the cost per health outcome averted compared to vaccinating persons aged ≥60 years in all the contiguous United States. This approach could potentially prevent 37% of all neuroinvasive disease cases and 63% of WNV-related deaths nationally. Employing such a threshold at a county-level further improved cost-effectiveness ratios while preventing 19% and 30% of WNV-related neuroinvasive disease cases and deaths, respectively.

CONCLUSIONS

An age- and incidence-based WNV vaccination program could be a more cost-effective strategy than an age-based program while still having a substantial impact on lowering WNV-related morbidity and mortality.

West Nile Virus Infection

Although long recognized as a human pathogen, West Nile virus (WNV) emerged as a significant public health problem following its introduction and spread across North America. Subsequent years have seen a greater understanding of all aspects of this viral infection. The North American epidemic resulted in a further understanding of the virology, pathogenesis, clinical features, and epidemiology of WNV infection. Approximately 80% of human WNV infections are asymptomatic. Most symptomatic people experience an acute systemic febrile illness; less than 1% of infected people develop neuroinvasive disease, which typically manifests as meningitis, encephalitis, or anterior myelitis resulting in acute flaccid paralysis. Older age is associated with more severe illness and higher mortality; other risk factors for poor outcome have been challenging to identify. In addition to natural infection through mosquito bites, transfusion- and organ transplant-associated infections have occurred. Since there is no definitive treatment for WNV infection, protection from mosquito bites and other preventative measures are critical. WNV has reached an endemic pattern in North America, but the future epidemiologic pattern is uncertain.

Cost effectiveness of a targeted age-based West Nile virus vaccination program

BACKGROUND

West Nile virus (WNV) is the leading cause of domestically-acquired arboviral disease in the United States. Several WNV vaccines are in various stages of development. We estimate the cost-effectiveness of WNV vaccination programs targeting groups at increased risk for severe WNV disease.

METHODS

We used a mathematical model to estimate costs and health outcomes of vaccination with WNV vaccine compared to no vaccination among seven cohorts, spaced at 10year intervals from ages 10 to 70years, each followed until 90-years-old. U.S. surveillance data were used to estimate WNV neuroinvasive disease incidence. Data for WNV seroprevalence, acute and long-term care costs of WNV disease patients, quality-adjusted life-years (QALYs), and vaccine characteristics were obtained from published reports. We assumed vaccine efficacy to either last lifelong or for 10years with booster doses given every 10years.

RESULTS

There was a statistically significant difference in cost-effectiveness ratios across cohorts in both models and all outcomes assessed (Kruskal-Wallis test p<0.0001). The 60-year-cohort had a mean cost per neuroinvasive disease case prevented of $664,000 and disability averted of $1,421,000 in lifelong model and $882,000 and $1,887,000, respectively in 10-year immunity model; these costs were statistically significantly lower than costs for other cohorts (p<0.0001). Vaccinating 70-year-olds had the lowest cost per death averted in both models at around $4.7 million (95%CI $2-$8 million). Cost per disease case averted was lowest among 40- and 50-year-old cohorts and cost per QALY saved lowest among 60-year cohorts in lifelong immunity model. The models were most sensitive to disease incidence, vaccine cost, and proportion of persons developing disease among infected.

CONCLUSIONS

Age-based WNV vaccination program targeting those at higher risk for severe disease is more cost-effective than universal vaccination. Annual variation in WNV disease incidence, QALY weights, and vaccine costs impact the cost effectiveness ratios.

Mosquito Avoidance Practices and Knowledge of Arboviral Diseases in Cities with Differing Recent History of Disease

As the range of dengue virus (DENV) transmission expands, an understanding of community uptake of prevention and control strategies is needed both in geographic areas where the virus has recently been circulating and in areas with the potential for DENV introduction. Personal protective behaviors such as the use of mosquito repellent to limit human-vector contact and the reduction of vector density through elimination of oviposition sites are the primary control methods for Aedes aegypti, the main vector of DENV. Here, we examined personal mosquito control measures taken by individuals in Key West, FL, in 2012, which had experienced a recent outbreak of DENV, and Tucson, AZ, which has a high potential for introduction but has not yet experienced autochthonous transmission. In both cities, there was a positive association between the numbers of mosquitoes noticed outdoors and the overall number of avoidance behaviors, use of repellent, and removal of standing water. Increased awareness and perceived risk of DENV were associated with increases in one of the most effective household prevention behaviors, removal of standing water, but only in Key West.

West Nile Virus: A Challenge for Transplant Programs

West Nile virus is a new challenge for transplant programs worldwide. It is a mosquito-borne disease, which has become increasingly prevalent in North America since it was first recognized in New York in 1999. A review of a case study and the literature shows that the morbidity and mortality associated with West Nile virus infection and transplant recipients are alarmingly high. Treatment options are limited because of transplant programs' limited experience in working with this virus. Transplant programs must develop action plans for education on West Nile virus and its prevention to decrease the risk of infection among their transplant recipients.

Perceptual influences on self-protective behavior for West Nile virus, a survey in Colorado, USA

Background

The endemic state of West Nile virus (WNv) in North America underscores the need to examine mechanisms influencing human self-protective behavior. Based on previous findings and theory, this study is designed to achieve two specific aims. First, the study will examine self-protective behavior for WNv through a hybridized treatment of the Health Belief Model that includes cognitive, affective, ecological, and proximity risk perception measures. Second, within the resulting hybridized model explore the role of ethnicity in self-protective behavior for WNv.

Methods

Data were collected in Greeley, Colorado, using a self-administered mail survey. 384 completed surveys were returned (49 % completion rate). The questionnaire used items on cognitive-affective risk perception, ecological and proximity risk perception constructs, the Health Belief Model and demographics.

Results

Analysis revealed that newer risk perception models (ecological and proximity) provide some power to explain protective behavior. The psychometric measures of risk perception (cognitive and affective components) provided the best explanatory power. Self-protective behavior was further enhanced by the perception of benefits associated with such actions and the exposure to information cues to action. Hispanic/Latinos demonstrate greater perception of risk/susceptibility and greater exposure to information cues to action, and were more likely to practice self-protective behavior.

Conclusions

The findings in this study point to several useful openings for effective public health communication and intervention for WNv based on affective response, information exposure, and ethnicity. The results also have relevance for vectored diseases generally. It is becoming clear that changes in global climate will bring increased threat from mosquito vectored diseases. Mosquito protection will be an increasingly salient topic for public health communicators in the coming years.

West nile virus in the United States - a historical perspective

Prior to 1999, West Nile virus (WNV) was a bit player in the screenplay of global vector-borne viral diseases. First discovered in the West Nile District of Uganda in 1937, this Culex sp.-transmitted virus was known for causing small human febrile outbreaks in Africa and the Middle East. Prior to 1995, the last major human WNV outbreak was in the 1950s in Israel. The epidemiology and ecology of WNV began to change in the mid-1990s when an epidemic of human encephalitis occurred in Romania. The introduction of WNV into Eastern Europe was readily explained by bird migration between Africa and Europe. The movement of WNV from Africa to Europe could not, however, predict its surprising jump across the Atlantic Ocean to New York City and the surrounding areas of the United States (U.S.). This movement of WNV from the Eastern to Western Hemisphere in 1999, and its subsequent dissemination throughout two continents in less than ten years is widely recognized as one of the most significant events in arbovirology during the last two centuries. This paper documents the early events of the introduction into and the spread of WNV in the Western Hemisphere.

Self-reported protective behaviour against West Nile Virus among pregnant women in Toronto

OBJECTIVE

West Nile virus (WNV) is an emerging infection that can lead to substantial morbidity and mortality. Although data are limited with respect to the risk to the fetus and neonate, this risk is not inconsequential. Methods to reduce the risk of mosquito bites and WNV transmission are simple, economical, and effective in the non-pregnant population. The objective of this descriptive cross-sectional study was to assess adherence to protective behaviours against WNV in pregnant women and to determine predictors for such adherence.

METHODS

A questionnaire was administered to all consenting pregnant women at two Toronto university hospitals.

RESULTS

The majority of women reported practising behaviours that reduce the risk of mosquito bites and potentially of WNV infection. In this survey, between 40% and 80% of pregnant women avoided the outdoors, avoided areas with mosquitoes, and reported practising two or more personal protection behaviours. However, only 33% of pregnant women reported wearing mosquito repellent, with the majority expressing concern about the safety of repellent use during pregnancy. The majority of pregnant women cited the media or the Internet as a source of their knowledge about WNV; only 12% reported their physician as a source of such knowledge.

CONCLUSION

The majority of pregnant women are aware of WNV and practise protective behaviours that reduce the risk of transmission. However, they have unjustified fetal safety concerns about the use of mosquito repellent and are thus less likely to use it.

Early clinical features of dengue infection in Puerto Rico

Early diagnosis of dengue is challenging because the initial symptoms are often non-specific, viraemia may be below detectable levels and serological tests confirm dengue late in the course of illness. Identifying dengue early in the clinical course could be useful in reducing dengue virus transmission in a community. This study analyzed data from 145 laboratory-positive and 293 laboratory-negative dengue cases in Puerto Rico to define the early clinical features of dengue infection in children and adults and to identify the clinical features that predict a laboratory-positive dengue infection. Among children, rash and age were independently associated with laboratory-positive dengue infection. Rash in the absence of cough had a positive predictive value of 100% and a negative predictive value of 82.4% as a paediatric dengue screen. Among adults, eye pain, diarrhoea and absence of upper respiratory symptoms were independently associated with laboratory-positive dengue infection. No useful early predictors of dengue infection among adults were found. Using clinical features may promote earlier identification of a subset of paediatric dengue patients in Puerto Rico. Laboratory confirmation is still necessary for the accurate diagnosis of dengue infection.

Estimates of worst case baseline West Nile virus disease effects in a suburban New York county

Serosurveys conducted where West Nile Virus (WNV) caused health impacts were used to construct a model of potential worst case health impacts in a suburban setting. This model addressed two common public perceptions regarding mosquito control activities and WNV disease: it is not a disease of major consequence, and exposed populations quickly become immune. Comparisons to blood bank infection and serious disease incidence data were similar to some of the serosurvey model results. Accounting for theoretical increasing immunity, even over a 20-year period, did not substantially reduce the potential impacts. The model results were approximately an order of magnitude greater than those actually experienced in Suffolk County, NY; differences in mosquito populations and/or the degree of mosquito control between Suffolk County and serosurvey sites seem to be the reason for the differences.

West Nile virus infection among the homeless, Houston, Texas

Among 397 homeless participants studied, the overall West Nile virus (WNV) seroprevalence 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 need to be directed toward this high-risk population.

Behavioral risks for West Nile virus disease, northern Colorado, 2003

Protective practices may affect the level of illness in a community.

In 2003, residents in 2 adjacent cities in northern Colorado (Loveland and Fort Collins) had severe outbreaks of human West Nile virus (WNV) disease. Unexpectedly, age-adjusted neuroinvasive disease rates were higher in Loveland (38.6 vs. 15.9 per 100,000), which had a more extensive mosquito control program and fewer mosquitoes. A survey was conducted to assess differences in personal protection and risk practices by each city's residents. During May and June 2004, a random-digit dial telephone survey was conducted among adults to assess personal protection behavioral practices used to prevent WNV infection during the 2003 outbreak. After we adjusted for identified risk factors, Loveland residents were 39% more likely to report seldom or never using N,N-diethyl-m-toluamide (DEET), and ≈30% were more likely to report being outdoors during prime mosquito-biting hours than Fort Collins residents. Personal protective practices may directly influence rates of WNV infection and remain important even when comprehensive community mosquito control measures are implemented.

Human west nile virus neuroinvasive disease in Texas, 2003 epidemic: regional differences

PURPOSE

Arboviral diseases, such as West Nile virus (WNV) epizootics, tend to be geographically unique because of the biomes that support the vector(s) and reservoir host(s). Understanding such details aids in preventive efforts. We studied the 2003 epidemic of human West Nile neuroinvasive disease (WNND) in Texas because it initially appeared that incidence was not uniform across regions of the state.

METHODS

The epidemic was described by age, sex, and region of residence. These variables were used to compare age-specific incidence, standardized cumulative incidence, and age-adjusted relative risk (RR). We verified case data and used routine software, with population estimates from the US Census Bureau.

RESULTS

Regardless of sex, risk increased with age. Males had the greater risk (RR, 1.69); however, males aged 5 to 17 years had the greatest RR. Of the five regions compared, two posed more (RRs, 7.98 and 2.14) and one posed less (RR, 0.40) risk than the remainder of the state. Proportions of Culex vector species differed significantly between regions.

CONCLUSIONS

During 2003, the risk for WNND varied considerably across Texas. This suggests that various risks for WNV infection deserve additional research for preventive interventions to be regionally appropriate and effective.

Environmental and ecological determinants of West Nile virus occurrence in horses in North Dakota, 2002

West Nile virus (WNV) outbreak in North Dakota in 2002 included over 569 horse cases, clustered mainly in the eastern and northeastern parts of the state. The pattern of occurrence observed suggested existence of specific environmental and ecological factors that increased the risk for infection and illness in those locations. We developed a predictive model with factors that explained the pattern of WNV occurrence observed. Results indicated that surface elevation, temperature, precipitation, reported WNV-positive birds, reported WNV-positive humans, and reported WNV-positive mosquitoes were important predictors of occurrence in horses. However, case distance from water bodies was not significant in the model. Future predictive models of WNV occurrence in horses should take into account these factors in order to improve accuracy and reliability. Research into other potential determinants such as horse management factors are required to determine more differential risk factors associated with WNV occurrence in horses.

West Nile virus infection among health-fair participants, Wyoming 2003: assessment of symptoms and risk factors

Wyoming experienced heavy West Nile virus (WNV) activity for the first time in 2003 and the area hardest hit was Goshen County. Little was known about the epidemiology of WNV in this region. This study describes the symptomatology of WNV and the association between certain behaviors and infection in Goshen County. Study participants were recruited from attendees of a health-fair sponsored by a local hospital, held October 1-3, 2003. A blood sample for WNV testing was obtained from each participant, and participants completed a questionnaire seeking information about the presence of specified symptoms consistent with WNV infection and risk factors possibly associated with infection. The samples were tested for anti-WNV IgM and IgG at the Wyoming Public Health Laboratory. Eight-hundred sixty-nine residents of Goshen County participated, and 122 (14.0%) were seropositive for anti-WNV IgM or IgG. Sixty (59.4%) of 101 persons seropositive for anti-WNV IgM experienced at least one symptom in the previous 4 months consistent with WNV infection, compared with 323 (43.2%) of 747 seronegative persons, resulting in an attributable risk of WNV seropositivity of 16.2%. Of the many symptoms queried, muscle aches (OR 2.63, 95% CI 1.69-4.09), skin rash (OR 6.35, 95% CI 3.74-10.80), fever (OR 2.56, 95% Cl 1.50-4.36), and muscle weakness (OR 2.33, 95% CI 1.34-4.02) were significantly associated with seropositivity on univariate analysis. By multivariate analysis, only skin rash remained significant. Risk factor analysis showed those spending > or =3 hours outside per day were more likely to be seropositive than those spending less time outside per day ( p < 0.05). This study corroborates the belief that a minority of persons infected with WNV develop symptoms attributable to WNV, and also demonstrates that some symptoms are more significantly associated with infection than others.

Manifestations of West Nile neuroinvasive disease

Since its introduction to North America in 1999, West Nile virus, an arthropod-borne flavivirus, has become the most significant cause of epidemic encephalitis in the western hemisphere. While most human infections with the virus are asymptomatic and the majority of symptomatic persons experience febrile illness, severe neurologic manifestations, including meningitis, encephalitis, and poliomyelitis may be seen. This review summarizes the virology, epidemiology and pathogenesis of human infection with West Nile virus, and details recent advances in our understanding of the pathophysiology and various clinical manifestations of infection.

Assessing parents' perception of children's risk for recreational water illnesses

Understanding people's risk perceptions and motivations to adopt preventive behavior is important in preventing the spread of recreational water illnesses (RWI) and other emerging infectious diseases. We developed a comprehensive scale measuring parents' perceived risk of their children contracting RWI. Parents (N = 263) completed a self-administered questionnaire with scale items based on 4 constructs of the Protection Motivation Theory: perceived vulnerability, perceived severity, response efficacy, and self-efficacy. Exploratory factor analysis identified 7 underlying factors, indicating 7 subscales of perceived risk for RWI. Cronbach α ranged from 0.60 to 0.81. The Precaution Adoption Process Model supported scale construct validity. This study provides the first perceived risk scale for exploring psychosocial factors that may predict or mediate the adoption of behaviors that prevent the spread of infectious diseases contracted by children while swimming. Findings from this study also provide implications for encouraging preventive behavior against other emerging infectious diseases.

West Nile Virus: the buzz on Ottawa residents' awareness, attitudes and practices

BACKGROUND

In 2002, the City of Ottawa was interested in the public perception of West Nile Virus (WNV) and mosquito control. Their objectives were to assess: awareness of WNV, practices to reduce mosquito sources, personal protective measures, and attitudes towards community-based insecticide programs.

METHODS

In July 2002, we administered a telephone survey to a random, stratified sample of urban, suburban and rural Ottawa households.

RESULTS

Surveys were completed for 491 households. Most (77.2%) respondents reported they had heard of WNV, and of these, 58.3% reported WNV was an important health issue. Mosquito repellent was the most common personal protective measure, reported among 72.5% of respondents, of whom 76.9% used DEET products. Multivariate regression analyses showed that age was a significant predictor of repellent use, with respondents aged less than 51 years more likely to use repellent than older respondents (ORadj =2.0; 95% CI: 1.2-2.3). This age group was also more likely to use at least one personal protective behaviour (ORadj = 2.5; 95% CI: 1.4-4.5). Of 315 people selecting a justified time to larvicide, 4.8% chose "larvicides should never be used in Ottawa"; 33.4% stated that larviciding would be appropriate "when WNV was detected in birds or mosquitoes"; one third "needed more information" on the health and environmental effects of insecticides, prior to selecting a response.

CONCLUSIONS

Our findings highlight the need for public education reinforcing WNV importance, emphasizing the health and environmental effects of insecticides as well as appropriate personal protective behaviours. Such messages should target older and urban residents.

Protective behavior survey, West Nile virus, British Columbia

We investigated personal protective behaviors against West Nile virus infection. Barriers to adopting these behaviors were identified, including the perception that DEET (N,N-diethyl-m-toluamide and related compounds) is a health and environmental hazard. Televised public health messages and knowing that family or friends practiced protective behaviors were important cues to action.