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THE BURDEN OF CHIKUNGUNYA VIRUS
INFECTION: THE NEED FOR SYSTEMATIC AND
To the Editor: In their letter in response to our review,
Godeart and colleagues
have underlined the way by
which we have estimated the potential burden of Chikun-
gunya virus (CHIKV) infection in older people. Evidence
from epidemiological, clinical, and laboratory studies sug-
gest an age-related defect in the immune system inducing a
state of susceptibility and vulnerability to new or emerging
With respect to arboviral diseases, in addition
to infants, older adults are often the first affected with the
highest incidence of severe and atypical cases.
example, in the first outbreak of West Nile Virus in the
United States in 1999, the median age was 71, with 73%
of those affected aged 60 and older.
In 2000 in Israel, all
of the victims were aged 78 and older.
Similar trends can
be drawn in the United States with California encephalitis,
dengue, Eastern equine encephalitis, St. Louis encephalitis,
yellow fever, and Zika, which are also spread by mosqui-
For CHIKV, data are less abundant and conclusive.
As detailed by Godeart and colleagues
and in our
the effect of the age-associated remodeling of the
immune system probably contributes to the highest inci-
dence of atypical presentation at the acute stage of
In the absence of serological confirma-
tion or more specific diagnostic criteria for older adults,
Figure 1. Schema of disease development and assessment at older population-level older population-level disease for chikungunya
virus (CHIKV) infection. Individuals susceptible to CHIKV infection (immunologically na
ıve population) exposed to the bite of
infected Aedes albopictus or A. aegypti mosquitoes will develop infection, which may become symptomatic or remain nonsymp-
tomatic. CHIKV can also be spread from a human to an uninfected mosquito and to a human again, contributing to the urban
cycle of infection. Transmission studies, usually based on serological testing, provide evidence of past and present CHIKV infec-
tion, but they do not quantify human disease (i.e., this type of study does not permit to distinguish symptomatic from asymp-
tomatic cases) or the induced disability. Symptomatic diseases (acute or chronic) related to the direct effect of CHIKV
pathogenesis or indirectly through the exacerbation and deterioration of comorbid and disabling conditions and specific mortal-
ity may be counted actively (e.g., by CHIVK epidemic forecast observatory) or passively (through healthcare system statistics or
case series reports), YLL 5 years of healthy-life lost; YLD 5 years lost due to disability. Adapted from LaBeaud et al.
figure can be viewed at wileyonlinelibrary.com]
This letter comments on the letter by Lidvine Godaert et al.
JAGS MARCH 2018–VOL. 66, NO. 3 LETTERS TO THE EDITOR 635