Estimated Incubation Period for Zika Virus Disease

Elisabeth R. Krow-Lucal; Brad J. Biggerstaff; J. Erin Staples

Emerging Infectious Diseases. 2017;23(5):841-845.

Abstract and Introduction

Abstract

Information about the Zika virus disease incubation period can help identify risk periods and local virus transmission. In 2015–2016, data from 197 symptomatic travelers with recent Zika virus infection indicated an estimated incubation period of 3–14 days. For symptomatic persons with symptoms >2 weeks after travel, transmission might be not travel associated.

Introduction

Zika virus is a mosquito-borne flavivirus transmitted primarily through the bite of infected Aedes spp.mosquitoes. Transmission can also occur through occupational laboratory exposure and by intrauterine, intrapartum, or sexual routes.^[1–3]

In May 2015, Zika virus disease cases were identified in Brazil, representing the first local transmission in the Americas.^[4] Subsequently, Zika virus spread rapidly, resulting in >463,000 suspected and laboratory-confirmed cases in the Americas as of June 30, 2016.^[5] This rapid expansion highlighted key knowledge gaps, including incubation period. Characterizing the incubation period for Zika virus is needed for defining periods of risk and identifying local virus transmission. To estimate the incubation period, we used data from symptomatic persons who had traveled to an area with ongoing Zika virus transmission and for whom laboratory evidence indicated recent infection.

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Next Section

Abstract and Introduction
The Study
Conclusions
References

Table. Demographics, travel data, and laboratory testing results for Zika virus disease patients, United States, January 1, 2015, through June 23, 2016
Patient characteristic	All cases, no. (%), n = 197*	Confirmed cases, no. (%), n = 79†
Age, y
0–19	19 (10)	10 (13)
20–39	71 (36)	29 (37)
40–59	79 (40)	32 (40)
>60	27 (14)	7 (9)
Unknown	1 (<1)	1 (1)
Sex
M	77 (39)	26 (33)
F	119 (60)	52 (66)
Unknown	1 (1)	1 (1)
Pregnant
Yes	11 (6)	2 (3)
No	161 (82)	60 (76)
Unknown	25 (13)	17 (22)
Travel duration, d
<7	24 (12)	15 (19)
7–13	88 (45)	64 (81)
14–20	31 (16)	0
21–27	12 (6)	0
≥28	42 (21)	0

*Persons with Zika virus–like symptoms and positive results for Zika virus RNA by real-time reverse transcription PCR or positive results for Zika or dengue virus IgM and Zika virus plaque reduction neutralization test (PRNT) results ≥10 and Zika virus titer ≥4-fold higher than dengue virus titer.
†Persons who traveled <2 weeks, experienced Zika virus–like symptoms, and had positive Zika virus RNA results by real-time reverse transcription PCR or positive Zika or dengue virus IgM results and PRNT ≥10 and dengue PRNT <10.