Differential Shedding and Antibody Kinetics of Zika and Chikungunya Viruses, Brazil

The StudyWe prospectively sampled patients in 4 time points up to 90 days post-symptom onset (dpo) (Table 1; Figure 1, panel A; Appendix, https://wwwnc.cdc.gov/EID/article/25/2/18-0166-App1.pdf).The cohort comprised 15 patients with acute Zika virus infection (5 male, 10 female; median age 39.0 years [interquartile range 31.0-44.0years]) and 18 patients with acute CHIKV infection (10 male, 8 female; median age 39.0 years [interquartile range 31.0-57.3years]), determined by detection of viral RNA in blood or urine 1-9 dpo (Appendix Figures 1, 2).All Zika virus belonged to the Asian lineage (2), and all CHIKV to the East/Central/South African lineage, according to envelope-based typing.At enrollment, Zika virus patients most frequently reported fever, rash, and arthralgia (80% each), and CHIKV patients most frequently reported arthralgia (100%), fever (89%), and myalgia (89%) (Table 2).No co-infection with Zika virus, CHIKV, or DENV was detected by real-time reverse transcription PCR (rRT-PCR).However, serologic analyses found that 4 (27%) Zika virus-infected patients also had CHIKV IgM at enrollment, and 1 (7%) had DENV IgM (Appendix Table 1, Figure 3).Similarly, 3 (17%) CHIKV-infected patients had Zika virus IgM, and 4 (22%) CHIKV-infected patients had DENV IgM at enrollment (Appendix Figure 4).We cannot exclude the possibility of cross-reactivity between Zika virus-specific and DENVspecific antibodies because 2 CHIKV patients simultaneously showed Zika virus and DENV IgM in an envelopebased ELISA (Appendix Table 2).Seventy-nine percent of Zika virus and 83% of CHIKV patients showed serologic evidence for past DENV infection at enrollment (Appendix Figures 1, 2).Thus, recent infections with heterologous arboviruses might bias attributing infection-specific symptoms for Zika virus and CHIKV.Consistent with previous studies (4,9), Zika virus loads in serum and urine were low up to 9 dpo (≈10 4 RNA copies/mL) (Figure 1, panel B), whereas CHIKV loads were ≈100-fold higher (≈10 6 RNA copies/mL) (Figure 1, panel C).However, unlike with Zika virus, CHIKV loads decreased significantly (p<0.001 by t test) from 5 dpo onward, and viral loads in urine were consistently low (Figure 1, panels D, E).