A comparison of Zika and dengue outbreaks using national surveillance data in the Dominican Republic

Abstract

BackgroundAedes-borne arboviruses continue to precipitate epidemics worldwide. In Dominican Republic, the appearance of Zika virus cases that closely followed a large dengue epidemic provided an opportunity to study the different transmission drivers behind these two flaviviruses. Retrospective datasets were used to collect information on the populations at risk and descriptive statistics were used to describe the outbreaks on a national scale.Methodology/ Principal findingsExpectedly, box plots showed that 75% of dengue was reported in those aged <20 years while Zika infections were more widely dispersed among the population. Dengue attack rates were marginally higher among males at 25.9 per 10,000 population vs. 21.5 per 10,000 population for females. Zika infections appeared to be highly clustered among females (73.8% (95% CI 72.6%, 75.0%; p<0.05)); age-adjusted Zika attack rates among females were 7.64 per 10,000 population compared with 2.72 per 10,000 population among males. R0 calculations stratified by sex also showed a significantly higher metric among females: 1.84 (1.82, 1.87; p<0.05) when compared to males at 1.72 (1.69, 1.75; p<0.05). However, GBS attack rates stratified by sex revealed slightly higher risk in males vs. females, at 0.62 and 0.57 per 10,000 population respectively.Conclusions/ SignificanceEvidence suggests little impact of existing dengue immunity on reported attack rates of Zika at the population level. Confounding of R0 and incident risk calculations by sex-specific over-reporting can alter the reliability of epidemiological metrics, which could be addressed using associated proxy syndromes or conditions to explore seemingly sex-skewed incidence. The findings indicate that community awareness campaigns, through influencing short-term health seeking behaviour, remain the most plausible mechanism behind increased reporting among women of reproductive age, although biological susceptibility cannot yet be ruled out. Media campaigns and screening are therefore recommended for women of reproductive age during Zika outbreaks. Future research should focus on clinical Zika outcomes among dengue seropositive individuals.

Asynchronicity of endemic and emerging mosquito-borne disease outbreaks in the Dominican Republic

“…3a ). These findings are consistent with the epidemiology of the three diseases and previous estimates of R eff for chikungunya and Zika 26 , 42 , 43 . Published estimates of the basic reproduction number ( R 0 ) for dengue, equivalent to R eff in a wholly susceptible population, vary widely (0.97–65) owing to the parameter’s sensitivity to the size of the local susceptible population 44 .…”

“…The other two outbreaks were caused by emerging viruses, chikungunya and Zika (Seasons 3 and 5, respectively; Fig. 1b, c ) 26 . Those outbreaks were the first and only to be reported of either disease in the country, and the number of reported cases in the Caribbean as a whole plummeted in subsequent years 27 , 28 .…”

Epidemiologic and spatiotemporal trends of Zika Virus disease during the 2016 epidemic in Puerto Rico

“…As previously reported from Puerto Rico [ 43 ] and consistent with reports from other jurisdictions [ 3 , 40 , 44 , 45 ], adult females were over-represented among ZIKV disease patients. Although sexual transmission cannot be discounted as playing a role in this imbalance [ 46 ], a more likely explanation may be sex- and age-specific differences in frequency of developing symptomatic ZIKV infection [ 41 , 47 ].…”

“…During the 2016 Zika epidemic in Puerto Rico, 1% of residents of Puerto Rico were reported to public health authorities as having suspected ZIKV disease and had laboratory evidence of ZIKV infection. This rate is two-fold lower than that reported from Cabo Verde [39] and 10-fold higher than in the Dominican Republic [40], but may not reflect true differences in the magnitude of the epidemic. Rather, availability of surveillance and diagnostic resources in Puerto Rico may have resulted in increased case detection compared to other jurisdictions.…”

Human Schwann cells are susceptible to infection with Zika and yellow fever viruses, but not dengue virus

“…To evaluate the potential for direct ZIKV-induced peripheral nerve damage, we assessed the susceptibility of immortalized primary human Schwann cells (hSCs) 33 to infection with strains of ZIKV from Africa, Asia and Brazil. Infection with ZIKV was compared to infection with flaviviruses YFV 17D and DENV2 that are less commonly associated with GBS 34,35 . All strains of ZIKV and YFV, but not DENV2, replicated well in hSCs and induced innate responses and cytopathic effect.…”