Zika virus infection overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Nate Michalak, B.A.
Overview
Zika fever is an infectious disease caused by the Zika virus (ZIKV), an enveloped, single stranded positive sense RNA Flavidivirus. Zika virus is a vector-borne pathogen usually transmitted via the Aedes mosquito that also transmit the dengue and chikungunya viruses. Human-to-human transmission may be possible by sexual intercourse but has not been confirmed. Once rare, the incidence of Zika virus infection is thought to have risen dramatically, particularly in Brazil as observed by the manifestation of a correlated complication, microcephaly, in infants born to mothers with Zika virus infection. Zika virus infection's broad ranging clinical symptoms cause it to be commonly misdiagnosed with multiple similar diseases that are also from the Flaviviridae virus family. Zika virus infection has similar clinical presentation to Dengue fever, yellow fever, West Nile virus, and Japanese encephalitis. Zika virus infection is distinct in its milder clinical manifestations and short length of infection. Patients exposed to Zika virus will develop symptoms 3 and 12 days after contracting the disease. Symptoms will typically begin with a mild headache and progress to include a maculopapular rash spread across the body within 24 hours, followed by fever, malaise, and back pain. The symptoms typically last 4-7 days. The prognosis is excellent, with the majority of patients recovering fully. Complications include congenital and neurological sequelae, particularly Guillain-Barré syndrome and microcephaly. Diagnosis is usually made by either ELISA and PCR. Treatment is usually supportive, and antiviral therapy is generally not recommended. There are no vaccines against Zika virus. Since the virus is usually transmitted through mosquitoes, effective measures to avoid mosquito bites include using insect repellent, installing mosquito bed nets and window/door screens, wearing long sleeves and long pants, and removing potential breeding sites from indoor/outdoor premises. Once infected, individuals may be re-infected in the future.
Historical Perspective
Zika virus was first isolated from a rhesus Monkey in 1947 in Uganda. The virus was first isolated from humans in 1968 in Nigeria. Since then, viral circulation and outbreaks have been documented throughout Asia and Africa. The most recent outbreak occurred in Brazil in April 2015.
Pathophysiology
Zika virus is a vector-borne pathogen usually transmitted via the Aedes mosquito that also transmit the dengue and chikungunya viruses. Human-to-human transmission may be possible by sexual intercourse but has not been confirmed. Zika virus is thought to initially replicate in dendritic cells near the site of inoculation before spreading to lymph nodes and then the bloodstream. Guillain-Barré syndrome and congenital microcephaly have been loosely associated with Zika virus disease. The most potent risk factor in the development of Zika virus infection is travel to endemic areas. Other risk factors include exposure to infected individuals via blood transfusion, sexual intercourse, or vertically to fetuses from infected mothers.
Causes
Zika virus infection is cause by Zika virus, an enveloped, single stranded positive sense RNA virus. Zika virus is a type of flavivirus and is primarily transmitted through mosquitoes.
Classification
A schema for the classification of Zika virus infection is yet to be developed.
Differential Diagnosis
Zika virus infection's broad ranging clinical symptoms cause it to be commonly misdiagnosed with multiple similar diseases that are also from the Flaviviridae virus family. Zika virus infection has similar clinical presentation to Dengue fever, yellow fever, West Nile virus, and Japanese encephalitis. Zika virus infection is distinct in its milder clinical manifestations and short length of infection. The association between Zika virus infection and complications that include congenital anomalies and neurological syndromes is also distinctive. Of note, patients bitten by mosquitoes may be concomitantly infected with Zika virus and other mosquito-borne infections, and co-infection should always be considered.
Epidemiology and Demographics
In 2015, Zika virus infection outbreaks rose dramatically, particularly in Brazil as observed by the manifestation of a correlated complication, microcephaly, in infants born to mothers with Zika virus infection, an incidence of approximately 100 per 100,000 infants. The majority of Zika virus infection cases are reported in South Africa and Tropical Asia. As of 2014, Zika Virus infection outbreaks have also become more common in South America. Cases reported in other regions of the world are attributed to travel from areas with outbreaks. Zika virus infection affects all age groups, with newborn infants particularly vulnerable due to risk of transmission from the mothers upon birth.
Risk Factors
The most potent risk factor in the development of Zika virus infection is travel to endemic areas. Other risk factors include exposure to infected individuals via blood transfusion, sexual intercourse, or vertically to fetuses from infected mothers.
Natural History, Complications & Prognosis
Patients exposed to Zika virus will develop symptoms 3 and 12 days after contracting the disease. Symptoms will typically begin with a mild headache and progress to include a maculopapular rash spread across the body within 24 hours, followed by fever, malaise, and back pain. The symptoms typically last 4-7 days. The prognosis is excellent, with the majority of patients recovering fully. Complications include congenital and neurological sequelae, particularly Guillain-Barré syndrome and microcephaly.
Diagnosis
History and Symptoms
The most common symptoms of Zika virus include fever and maculopapular rash. Additional symptoms include arthralgia, conjunctivitis, myalgia, headache, retro-orbital pain, and vomiting.
Physical Examination
Physical examination of patients with Zika virus infection is usually remarkable for fever and a maculopapular rash that often includes the face, trunk, and extremities (may include the palms and soles). Other physical examination findings include non-purulent conjunctivitis and edema.
Laboratory Findings
The diagnosis of Zika virus infection is usually made by detection of elevated IgM and IgG Zika virus antibodies by ELISA or viral RNA by RT-PCR. Non-specific lab findings include elevated markers of inflammation, mild neutropenia, normal leukocyte count or mild leukocytosis with normal platelet count and liver function tests.
Other Diagnostic Studies
There are no other diagnostic studies associated with Zika virus infection.
Treatment
Medical Therapy
There is currently no antiviral treatment for Zika virus. Suggested therapy includes rest, fluids antipyretics and analgesics. NSAIDs should be avoided until dengue fever is ruled out as a potential diagnosis.
Surgery
Surgery is not recommended for the management of Zika virus infection.
Prevention
There are no vaccines against Zika virus. Since the virus is usually transmitted through mosquitoes, effective measures to avoid mosquito bites include using insect repellent, installing mosquito bed nets and window/door screens, wearing long sleeves and long pants, and removing potential breeding sites from indoor/outdoor premises. Once infected, individuals may be re-infected in the future.