Economic Burden of West Nile Virus Disease

Quebec, Canada, 2012-2013

Najwa Ouhoummane; Eric Tchouaket; Anne-Marie Lowe; Ann Fortin; Dahlia Kairy; Anne Vibien; Jessica Kovitz-Lensch; Terry-Nan Tannenbaum; François Milord


Emerging Infectious Diseases. 2019;25(10):1943-1950. 

In This Article


In this study, we estimated direct and indirect costs of WNV disease cases in Quebec, Canada, up to 2 years after the acute phase of WNV disease. We found that costs varied considerably according to disease manifestations. Patients with WNE accounted for the largest proportion of the total cost, which could be attributable mainly to their worse hospital course, including severe clinical manifestations, longer stay in the hospital, admission to the intensive care unit, and complications.[6] When we compared WNM with WNE patients, we found that WNE patients had lower indirect costs (absence from work), which could be explained by their older age (≈70% were retired at the time of their WNV infection vs. only 17% of patients with WNM).

Although most WNM patients were hospitalized, hospital costs accounted for only 38% of the total cost. WNM is generally associated with a favorable outcome and shorter hospital stay. However, in our study, WNM patients required more physician visits after hospitalization than patients with WNE or WNF. WNF patients accounted for only 3% of the total cost, which was mostly associated with the 5 hospitalized case-patients. For these patients, the median cost of hospitalization was similar to that for the 17 hospitalized WNM patients (p = 0.901) (Table 7). In our previous study,[6] we showed that hospitalized WNF patients had similar demographic and clinical profiles as WNE patients, and we assumed that some of them could have undetected mild neuroinvasive disease because 3 of 5 hospitalized WNF patients did not have a lumbar puncture. However, half of WNF patients had consulted only a clinic, and costs associated with their initial care were not available. Thus, the total WNF costs could be underestimated.

These results are similar to those reported by Staples et al.,[8] who estimated the initial and 5 years post-WNV infection costs among hospitalized patients in Colorado, USA, during 2003. These authors reported that initial costs were higher for AFP and WNE patients, and long-term costs were higher for AFP and WNM patients. However, this study focused on hospitalized case-patients and might not be a true reflection of all reported WNV patients. Two other studies have evaluated the economic burden of WNV outbreaks in the United States, but both evaluated only initial costs.[7,9]

When we extrapolated our results to all reported WNV cases in the province of Quebec, we estimated that WNV infections could cost ≈$1.7 million during an epidemic, such as during 2012; during a low activity year, such as 2013, the cost could be ≈$430,000. These results are consistent with those of the cost-effectiveness simulation study of Bonneau et al.,[10] which estimated total direct and indirect cost of ≈$400,000 during a hypothetical year of low activity (25 cases of WNV infection) and >$13 million during a hypothetical year of high activity (840 cases of WNV infection). In that analysis, direct costs included hospitalization, rehabilitation, and outpatient consultations, and indirect costs included productivity losses caused by absence from work and death.

Our study had several limitations. Although participation rate was high and participants were similar to nonparticipants, analyses by clinical categories were based on a small number of cases. However, this number is similar to those for 3 studies in the United States.[7–9] Some costs, such as initial consultations in private practice and medication expenses during follow-up, were not included because they were unavailable or they lacked precision. However, these costs accounted for a small proportion of total cost. Recall biases were also possible for costs incurred during follow-up.

Calculation of productivity losses varies between studies. Because of ethical issues related to the evaluation of productivity losses for a dead person (e.g., is an old person less worthy than a young person because of the fact that he or she is retired or less productive?),[15] we decided not to include the indirect costs associated with death in our results. This decision resulted in an underestimation of the WNV economic burden, particularly for WNE patients, because 10 of them plus 1 WNM patient died during their initial hospitalization. Grosse et al.[17] estimated for the United States the productivity value by age and sex on a daily, annual, and lifetime basis (in 2007 US dollars). Such productivity tables are not available for Canada and Quebec. However, when we used daily production values and age and sex distribution of Grosse et al.[17] for our cases, we estimated the loss of productivity caused by WNV deaths over a 2-year period after the infection. To take into account time preference, we applied a discount rate of 3%, 5%, and 8% and converted the results to 2013 Canadian dollars on the basis of methods suggested by Montmarquette and Scott[18] and Tchouaket et al..[19] These estimates ranged from $467,000 (3% discount rate) to $589,000 (8% discount rate) and would represent a 35% increase over costs we calculated (Table 5).

In comparison, Zohrabian et al.[7] calculated lifetime lost productivity for persons who died, and this productivity loss represented half of the total costs of illness. Staples et al.[8] valued productivity losses for those who died but not for older persons who were retired at the time of their illness, and evaluation led to lower indirect costs for WNE than for WNM. In their simulation study, Bonneau et al.[10] showed that nearly 70% of total costs were attributable to indirect costs (deaths and absence from work).

In summary, we found that the overall cost of WNV infection in Quebec was ≈1.7 million for 2012 (24 symptomatic cases) and ≈430,000 for 2013 (31 symptomatic cases) and that costs were significantly higher for patients who had more severe forms of disease. Our study provides information to government and public health organizations to make informed decisions regarding preventive and intervention programs for WNV infection. Public health monitoring of costs, both direct and indirect, associated with different clinical manifestations of infectious diseases is essential to enable adequate planning for public health policies and infectious diseases prevention and control programs.