Approximately 80% of patients are asymptomatic, and those with symptoms generally experience a mild, self-limited illness lasting 2 to 7 days.[13]Pan American Health Organization; World Health Organization. Provisional remarks on Zika virus infection in pregnant women: document for health care professionals. January 2016 [internet publication].
http://iris.paho.org/xmlui/handle/123456789/18600
[150]Lucey DR. Time for global action on Zika virus epidemic. BMJ. 2016 Feb 8;352:i781
http://www.bmj.com/content/352/bmj.i781
http://www.ncbi.nlm.nih.gov/pubmed/26856896?tool=bestpractice.com
Severe disease requiring hospitalisation is uncommon and the case fatality is low.[13]Pan American Health Organization; World Health Organization. Provisional remarks on Zika virus infection in pregnant women: document for health care professionals. January 2016 [internet publication].
http://iris.paho.org/xmlui/handle/123456789/18600
The presence of comorbidities may increase the risk of a fatal outcome, based on a few case reports.[14]Zonneveld R, Roosblad J, van Staveren JW, et al. Three atypical lethal cases associated with acute Zika virus infection in Suriname. IDCases. 2016 Jul 22;5:49-53.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5007293/
http://www.ncbi.nlm.nih.gov/pubmed/27630820?tool=bestpractice.com
However, fatal outcomes have been reported in healthy individuals.[208]Swaminathan S, Schlaberg R, Lewis J, et al. Fatal Zika virus infection with secondary nonsexual transmission. N Engl J Med. 2016 Nov 10;375(19):1907-09.
http://www.nejm.org/doi/full/10.1056/NEJMc1610613
http://www.ncbi.nlm.nih.gov/pubmed/27681699?tool=bestpractice.com
No fatalities have been reported in children.[149]Goodman AB, Dziuban EJ, Powell K, et al. Characteristics of children aged <18 Years with Zika virus disease acquired postnatally - US states, January 2015-July 2016. MMWR Morb Mortal Wkly Rep. 2016 Oct 7;65(39):1082-5.
https://www.cdc.gov/mmwr/volumes/65/wr/mm6539e2.htm?s_cid=mm6539e2_w
http://www.ncbi.nlm.nih.gov/pubmed/27711041?tool=bestpractice.com
The Centers for Disease Control and Prevention (CDC) confirmed the first Zika-related death in the Continental US in an elderly resident of Utah who contracted the virus during travel to an area with active transmission. The patient also had an undisclosed health condition and the exact cause of death is unknown.[209]Brent C, Dunn A, Savage H, et al. Preliminary findings from an investigation of Zika virus infection in a patient with no known risk factors - Utah, 2016. MMWR Morb Mortal Wkly Rep. 2016 Sep 16;65(36):981-2.
http://www.cdc.gov/mmwr/volumes/65/wr/mm6536e4.htm
http://www.ncbi.nlm.nih.gov/pubmed/27631467?tool=bestpractice.com
Prognosis for infants born with microcephaly is unclear; however, microcephaly due to other causes is associated with a range of neurodevelopmental issues. An estimate of the case fatality rate for infants with microcephaly associated with Zika virus infection is 8.3%.[210]Cunha AJ, de Magalhães-Barbosa MC, Lima-Setta F, et al. Microcephaly case fatality rate associated with Zika virus infection in Brazil: current estimates. Pediatr Infect Dis J. 2017 May;36(5):528-30.
http://www.ncbi.nlm.nih.gov/pubmed/28403061?tool=bestpractice.com
A study in 19 infants born with microcephaly in Brazil found that most infants had severe motor impairment and other functional difficulties at 19 to 24 months of age, including seizure disorders, respiratory disorders, hearing/vision impairment, and sleeping/feeding difficulties. These outcomes often occur together.[211]Satterfield-Nash A, Kotzky K, Allen J, et al. Health and development at age 19-24 months of 19 children who were born with microcephaly and laboratory evidence of congenital Zika virus infection during the 2015 Zika virus outbreak - Brazil, 2017. MMWR Morb Mortal Wkly Rep. 2017 Dec 15;66(49):1347-51.
https://www.cdc.gov/mmwr/volumes/66/wr/mm6649a2.htm
http://www.ncbi.nlm.nih.gov/pubmed/29240727?tool=bestpractice.com
A study of 1450 infants that used data from a US Zika registry found that 14% of 1-year-old children who were exposed to Zika virus in utero had health issues potentially related to virus exposure. Of these infants, 6% had at least one Zika-associated birth defect, 9% had at least one neurodevelopmental abnormality possibly associated with Zika virus exposure, and 1% had both. However, the authors noted that most children did not have evidence of all recommended evaluations, and therefore, additional anomalies may exist.[212]Rice ME, Galang RR, Roth NM, et al. Vital signs: Zika-associated birth defects and neurodevelopmental abnormalities possibly associated with congenital Zika virus infection — U.S. territories and freely associated states, 2018. MMWR Morb Mortal Wkly Rep. 2018 Aug 10;67(31):858-67.
https://www.cdc.gov/mmwr/volumes/67/wr/mm6731e1.htm?s_cid=mm6731e1_w
http://www.ncbi.nlm.nih.gov/pubmed/30091967?tool=bestpractice.com
Once people have recovered from infection, they are likely to be protected from future infections. There is no evidence to suggest that prior Zika virus infection poses a risk for birth defects in future pregnancies.[213]Centers for Disease Control and Prevention. Questions about Zika. October 2019 [internet publication].
https://www.cdc.gov/zika/about/questions.html