Zika virus

Background

• Single-stranded, positive-sense RNA virus in the Flaviviridae family, genus Flavivirus
• Discovered in 1947 in Zika Forest, Uganda
• Vector-borne infection carried primarily by Aedes aegypti mosquitoes, but possibly also Aedes albopictus mosquitoes
• Sexual transmission appears to be possible
• Now essentially endemic in tropics worldwide

Clinical Manifestations

• 75% are asymptomatic
• Incubation period of 3 to 14 days
• Fever, rash, arthralgias, conjunctivitis, and headache
• Usually self-limited, lasting around 5 days
• Can have neurological disease in some cases, primarily presenting as Guillain-Barré syndrome
• With maternal infection, causes a congenital syndrome of CNS abnormalities including microcephaly, intracranial calcifications, lissencephaly, pachygyria, and vision and hearing loss

Differential Diagnosis

• Dengue virus
• Chikungunya virus

Feature	Dengue	Zika	Chikungunya
Asymptomatic	40-80%	35-85%	3-28%
Fever	+++	++	+++
Rash	+	+++	++
Conjunctivitis	–	++	+
Arthralgia	+	++	+++
Myalgia	++	+	+
Headache	++	+	++
Hemorrhage	++	–	–
Shock	+	–	–
Thrombocytopenia	+++	+	–
Leukopenia	++	–	++

Investigations

• Serum rRT-PCR, ideally done within 10 days of symptoms onset
• Serology can be tested after 10 days of symptoms, but is non-specific

Management

• Supportive
• For risk of congenital disease
  • If asymptomatic, no need to delay attempts at conception
  • If symptomatic and diagnosis is confirmed, counsel to delay attempts at conception for 2 months (women) or 3 months (men) after return from the endemic area
  • If symptomatic and diagnosis is not confirmed, then discuss with the patient
  • If the woman is pregnant and man has compatible symptoms, should abstain from unprotected sex for the duration of pregnancy