Zika Virus

Most Zika infections are mild or silent, which is exactly why it's dangerous in pregnancy. The virus is linked to microcephaly (babies born with underdeveloped brains), Guillain-Barré syndrome, myelitis, and other neurologic conditions. Here's what to know about transmission, symptoms, diagnosis, treatment, prevention, and nursing care.

Zika was first identified in the Zika forest of Entebbe, Uganda in 1947, in a febrile rhesus monkey examined for yellow fever.

What is the Zika Virus?

Zika is a mosquito-borne flavivirus spread to humans mainly through the bite of an infected Aedes mosquito (Aedes aegypti and Aedes albopictus).

• Zika virus (ZIKV) belongs to the Flaviviridae family, Flavivirus genus.
• Most infections cause a mild, self-limited illness.
• Incubation is likely 3-12 days.
• The disease spectrum overlaps with other arboviral infections, but maculopapular rash (likely immune-mediated) usually predominates.
• In April 2016, a CDC deputy director warned that US risk had been underestimated, citing the mosquito vectors' expanded range (now in 30 US states, up from 12) and travel tied to the 2016 Olympics in Brazil.
• Nonhuman and human primates are the likely main reservoirs, and human-to-vector-to-human transmission occurs during outbreaks.

Pathophysiology

Zika adapts well across hosts, from arthropods to vertebrates.

• The E (envelope) glycoprotein mediates viral attachment to unidentified cellular receptors.
• Endocytic uptake follows, then uncoating of the nucleocapsid and release of viral RNA into the cytoplasm.
• A viral polyprotein is produced and modified by the endoplasmic reticulum.
• Immature virions collect in the endoplasmic reticulum and secretory vesicles before release.

Causes

Zika spreads mainly through the bite of an infected Aedes mosquito (Ae. aegypti and Ae. albopictus).

• Mosquitoes. A mosquito picks up the virus by biting an infected person while the virus is in their blood, typically only through the first week of infection, then spreads it to others through bites.
• Mother to child. An infected pregnant woman can pass the virus to her fetus during pregnancy or around birth.
• Sex. Zika passes through sex from an infected person to a partner, even when the infected person has no symptoms.
• Blood transfusion. Multiple possible transfusion-transmission cases have been reported in Brazil.
• Lab and healthcare exposure. Laboratory-acquired infections have been reported, though the route wasn't always clearly established.

Statistics and Incidences

Global prevalence is poorly reported because the illness is often asymptomatic, resembles other flavivirus infections (dengue, chikungunya), and is hard to confirm.

• In 2015 and 2016, large outbreaks hit the Americas, driving travel-associated cases in US states, widespread transmission in Puerto Rico and the US Virgin Islands, and limited local transmission in Florida and Texas.
• As of 2014, Zika had been reported in humans, primates, and mosquitoes across 14 countries in Africa, Asia, and Oceania.
• In May 2015, Brazil reported the first outbreak in the Americas.
• Brazil's Ministry of Health estimated 440,000-1,300,000 suspected cases in December 2015.
• In March 2016, the WHO reported Zika actively circulating in 38 countries and territories, 12 of which reported increased GBS cases or lab evidence of Zika in patients with GBS.
• As of June 2016, 591 laboratory-confirmed travel-associated infections had been reported in the United States, none from local vector-borne transmission.

Clinical Manifestations

Many infected people have no symptoms or only mild ones. The most common:

• Fever. Often within the first week of illness.
• Rash. Usually a fine, diffuse maculopapular rash that can involve the face, trunk, and extremities, including palms and soles; occasionally pruritic.
• Headache. Classically retroocular.
• Joint pain. Arthralgia in the small joints of the hands and feet.
• Conjunctivitis (red eyes). Self-limiting.
• Muscle pain. May last 2 to 7 days, like the other symptoms.

Assessment and Diagnostic Findings

Diagnosis uses both molecular and serologic methods.

• Nucleic acid amplification test. NAAT is the preferred method because it confirms infection by detecting viral genomic material.
• Zika virus antibody testing. IgM is variable but generally turns positive in the first week after symptom onset and continues up to 12 weeks post-onset or exposure, sometimes persisting for months to years.
• Plaque reduction neutralization tests (PRNT). These quantitative assays measure virus-specific neutralizing antibody titers; they resolve false-positive IgM results from nonspecific reactivity and can help identify the infecting virus.

Medical Management

There's no specific drug or vaccine for Zika.

• Medical care. Supportive: rest and adequate fluid hydration. Control fever and pain with acetaminophen.
• Consultations. In pregnancy, involve maternal-fetal medicine and infectious diseases specialists.
• Prevention. Best prevention is avoiding travel to areas with active transmission. To prevent bites: wear full-sleeved shirts and long pants, sleep under a mosquito bed net, and treat clothing with permethrin.

Nursing Management

Nursing Assessment

• History. Incubation is likely 3-12 days. More than 80% of infections likely go unnoticed because the disease is mild. Its spectrum overlaps with other arboviral infections, but maculopapular rash usually predominates.
• Physical exam. The WHO recommends measuring head circumference in newborns of infected mothers between 1 and 7 days after birth. A circumference more than 2 standard deviations below the mean is microcephaly; more than 3 standard deviations below the mean is severe microcephaly and should prompt neuroimaging.

Nursing Diagnosis

• Acute pain related to severe retroocular headache and joint pain.
• Hyperthermia related to increased metabolic rate and dehydration.
• Fluid volume deficit related to excessive sweating and dehydration.
• Knowledge deficit related to lack of information about the disease, treatment, and prognosis.

Nursing Care Planning and Goals

• Patient reports satisfactory pain control below 3 to 4 on a 0 to 10 scale.
• Patient maintains body temperature below 39° C (102.2° F).
• Patient explains measures to treat or prevent fluid volume loss.
• Patient and family explain the disease, recognize the need for medications, and understand treatment.

Nursing Interventions

• Relieve pain. Acknowledge reports of pain right away; remove added stressors and sources of discomfort; provide rest periods for sleep and relaxation; pick the right pain relief method; give analgesics as ordered and check effectiveness and adverse effects.
• Decrease fever. Remove excess clothing and covers; give antipyretics as prescribed; push oral fluids; provide a high-calorie diet as indicated; teach the patient and family the signs of hyperthermia and the factors behind fever; stress fluids to avoid dehydration.
• Maintain fluid volume. Urge the patient to drink the prescribed amount; emphasize oral hygiene; keep the patient comfortable with light covers; give parenteral fluids as prescribed; consider an IV fluid challenge with immediate infusion for abnormal vital signs; prevent excessive electrolyte loss (rest the GI tract, give antipyretics as ordered); teach the family to monitor intake and output at home.
• Educate patient and family. Provide a calm environment and an atmosphere of respect and trust; include the patient in building the teaching plan and setting goals up front; give clear explanations and demonstrations; start with simple, familiar, concrete information before moving to complex; allow repetition.

Evaluation

Goals are met when the patient reports pain control below 3 to 4 on a 0 to 10 scale, maintains body temperature below 39° C (102.2° F), explains how to treat or prevent fluid volume loss, and (with family) explains the disease and understands treatment.

Documentation Guidelines

• Individual findings, including contributing factors, interactions, and specifics of behavior.
• Cultural and religious beliefs and expectations.
• Plan of care.
• Teaching plan.
• Responses to interventions, teaching, and actions performed.
• Attainment or progress toward desired outcomes.

Summary

• Zika was first described in a febrile rhesus monkey in the Zika forest of Entebbe, Uganda.
• It spreads mainly through the bite of an infected Aedes mosquito (Ae. aegypti and Ae. albopictus); incubation is likely 3-12 days.
• An infected pregnant woman can pass the virus to her fetus during pregnancy or around birth.
• In 2015 and 2016, large outbreaks hit the Americas, with travel-associated cases in US states, widespread transmission in Puerto Rico and the US Virgin Islands, and limited local transmission in Florida and Texas.
• The most common symptoms are fever, rash, headache, joint pain, conjunctivitis, and muscle pain.
• Diagnosis uses both molecular and serologic methods.
• Supportive care is rest and fluids, with acetaminophen for fever and pain.

Sources

• Medscape, Zika Virus (2018). https://emedicine.medscape.com/article/2500035-overview
• Centers for Disease Control and Prevention, Zika Virus (2019). https://www.cdc.gov/zika/index.html