Recently, the World Health Organization (WHO) declared the ongoing outbreak of Zika virus and associated complications in the Americas, the Caribbean, and the Pacific a Public Health Emergency of International Concern, indicating the need for a coordinated international response.1 Local, state, national, and international healthcare organizations are rapidly scaling up their response to this outbreak.
Zika virus is typically transmitted by a mosquito bite. It usually causes a mild illness; however, several countries reporting active Zika virus are also reporting a significant rise in neurologic disorders such as microcephaly and Guillain-Barre syndrome (GBS).2 This has a direct and lasting impact on public health. Nurses must stay abreast of the evolving body of knowledge surrounding Zika virus infection in order to provide optimal care to their patients.
Epidemiology
Zika virus was first identified in Uganda in 1947 in rhesus monkeys and in humans in 1952.3 The virus is a single-stranded RNA virus of the Flaviviridae family. Flaviviridae viruses are found in vectors such as mosquitoes and can be transmitted to humans.4 Zika virus is related to other flaviviruses, including yellow fever virus, dengue virus, and West Nile virus.3
Large outbreaks of Zika virus infection have occurred as recently as 2013.3 The size of the recent outbreak and the possible relationship of Zika virus to significant neurologic disorders have garnered the attention of the Pan American Health Organization, the WHO, and the CDC, among others. Each of these organizations has activated emergency management systems to help direct research, intervention, and resources to the latest Zika virus outbreak.5-7
The rapid rise and widening geographic spread of vector-borne illnesses is attributed to numerous factors. International travel and trade contribute to the spread of disease. Travelers infected with a mosquito-borne illness can return to their native countries and infect others. In addition, vectors such as mosquitoes can survive in poor conditions. For example, mosquito larvae can survive on products that are traded internationally. In countries with circulating mosquito-borne illness, increased urbanization, poor public sanitation, and a de-emphasis on mosquito control programs over the past few decades contribute to the spread of disease. Insecticide resistance and alterations in environment also have been implicated as contributing factors.8,9
Transmission
Zika virus is an arthropod-borne virus (arbovirus); arthropod vectors include mosquitoes, ticks, and fleas. Rapid transmission of Zika virus among mosquito and human hosts is a hallmark of the latest outbreak.2 Once a mosquito is infected with Zika virus, the virus replicates in the mosquito's gut, rendering it capable of passing the virus on to a human with its bite.
Zika virus is transmitted to humans primarily via the bite of infected Aedes mosquitos, which live in all member states of the Americas except Canada and continental Chile.5,10 Two species within the Aedes mosquito genus are responsible for the transmission of Zika virus: Aedes aegypti and Aedes albopictus.10 These two species also transmit dengue virus, yellow fever virus, and chikungunya virus.11 The Aedes aegypti mosquito has evolved into a highly adaptive urban mosquito; numerous larvae can survive in a tiny amount of water.8 It is an aggressive daytime biter that feeds on human blood.4 Because it typically feeds in small amounts on multiple humans, it is a highly effective vector of disease. The CDC has also received reports of human-to-human transmission of Zika virus in utero, in the perinatal period, from sexual activity, and during blood transfusions.4
Diagnosis
There are numerous barriers to a rapid and accurate diagnosis of Zika virus infection. Because most patients infected are asymptomatic, guidelines for who should be tested are evolving. In the United States, the CDC provides updated guidelines about testing for Zika virus to healthcare providers.4 Patients with signs and symptoms consistent with Zika virus infection who have traveled to or lived in countries with circulating Zika virus within the past 2 weeks should be tested.4 Testing guidelines for special populations, such as pregnant women and infants and children, are discussed below.
Diagnostic tests for Zika virus cannot irrefutably detect the presence or absence of Zika virus in either the acute or convalescent stages of disease.12 This has significant implications for public health, especially when it comes to screening and educating the public to reduce human-to-human transmission of Zika virus. In addition, testing needs to be done in conjunction with local or state health departments, where available, or at the CDC Arbovirus Diagnostic Laboratory.13
A serum real-time reverse transcription-polymerase chain reaction (rRT-PCR) may detect Zika virus RNA in the blood early in the disease progression, but is of limited value for diagnosis later in the course of the disease or during convalescence.13 Zika virus serologic testing (Zika virus immunoglobulin M and neutralizing antibody titers) can be performed later. Recently, the CDC stated that urine should be collected, in addition to blood, for rRT-PCR testing. It is thought that Zika virus RNA remains present in the urine for up to 14 days after onset of symptoms. This is about a week longer than the Zika virus RNA remains in the blood.14
Clinical manifestations and treatment
The incubation period of Zika is unknown, but is estimated to be between a few days to 2 weeks.3 Eighty percent of those infected with Zika virus will have no signs and symptoms.4 Patients who are symptomatic typically experience mild signs and symptoms that include a low-grade fever, a maculopapular rash, conjunctivitis, myalgia, arthralgia, fatigue, and headache.3,4 Symptoms last for 2 to 7 days.3 Severe signs and symptoms that require hospitalization are rare and mortality is low.4
No antiviral medication or other specific treatment is available to treat Zika virus infection.4 Supportive care includes symptom management with rest, fluids, antipyretics, and analgesics.3 Avoid the use of aspirin and other nonsteroidal anti-inflammatory drugs until dengue virus infection has been ruled out to avoid hemorrhagic complications.4
Complications
Microcephaly, fetal loss, infant mortality, and GBS have all been linked to Zika virus infection.2,5,15 In April 2016, the CDC confirmed a causal relationship between Zika virus and microcephaly, based on a comprehensive review of existing research.16 Research that establishes or refutes a causal relationship of Zika virus to GBS and other complications is another significant and urgent focus of emergency public health initiatives.6,7
Microcephaly is a neonatal malformation in which infants are born with a head smaller than normal (decreased occipitofrontal circumference) due to abnormal brain development. Cases range from mild to severe. A host of neurologic complications are associated with microcephaly, including developmental delay; seizures; and speech, hearing, and vision deficits.17
GBS is an autoimmune disease that attacks the peripheral nervous system, resulting in progressive limb weakness and often flaccid paralysis. Most patients recover, though some will experience long-term disability. Mortality is about 5%. Many patients have a history of antecedent infection that triggers the immune response.18 It is possible that Zika is one such infection that has been linked with the rise in GBS in some countries in the Americas.19
Fetal mortality has also been linked to Zika virus.15 A handful of cases have been reported of fetal loss in the first trimester and live births with rapid demise to women who had recently traveled to countries with circulating Zika virus and/or had signs and symptoms consistent with Zika virus. Though the women were not necessarily tested for the virus, tissue samples from the fetuses and newborns tested positive for Zika virus.15
Prevention
Urgent emphasis on vaccine development is one of the features of the international response to the latest outbreak of Zika virus, but no vaccine is currently available.3,6 Nurses should discuss disease transmission with patients who are diagnosed with Zika virus infection. The length of time a patient remains infective is still unknown.
The focus of Zika virus prevention is on encouraging personal habits to decrease human/mosquito interactions. Recommendations include identifying and destroying mosquito breeding sites; wearing long-sleeved shirts and pants; and using insect repellant, permethrin-treated bedding, and screened-in or air-conditioned rooms.3,20
Women of reproductive age who are not pregnant should discuss reproductive planning in light of the Zika virus with their healthcare provider.21 Men who live in or travel to countries with circulating Zika virus should abstain from intercourse or correctly utilize condoms for all sexual activity with pregnant partners.21 Even men without pregnant partners should consider abstinence or condom usage for an unspecified amount of time. It is currently unknown how long Zika virus may be present in semen.22
In mid-May 2016, the CDC reported that there were 157 pregnant women in the United States and 122 pregnant women in the U.S. territories with lab evidence of Zika virus infection.23 These cases are both from symptomatic and asymptomatic women. Surveillance systems have been set up to monitor these women through their pregnancy to determine pregnancy and congenital outcomes. The majority of these cases are associated with travel to Zika-affected areas, though some are cases of sexual transmission. There are also some cases of local transmission in U.S. territories. To date, there have been no cases of local transmission in the United States. The CDC intends to update these numbers weekly.23
The WHO has issued no travel or trade restrictions for the countries currently experiencing circulating Zika virus.6 The CDC has issued a series of travel warnings, alerting travelers to affected areas to:20
* be aware of the situation in the country.
* protect themselves from mosquito bites.
* use condoms to mitigate possible sexual transmission of Zika virus.
* follow testing guidelines after travel to the affected areas.
The CDC has not yet recommended a travel ban to affected countries; however, it has advised high-risk populations, such as pregnant women, to consider delaying their travel to countries with circulating Zika virus.20
Nursing considerations
The CDC has published a series of detailed guidelines for screening and management of patients who may have or have been exposed to Zika virus. These guidelines are updated as more evidence emerges from the current outbreak, and they have direct impact on the screening and management of affected patients. Guidelines include the prevention of sexual transmission, care of pregnant women and women of reproductive age with possible Zika virus exposure, and caring for infants and children with possible Zika virus infection.21,22,24 Clinicians should consult the most recent information for specific management algorithms (http://www.cdc.gov/zika/hc-providers).
An evolving concern
Much remains to be learned about Zika virus, the latest emerging, vector-borne infectious disease. Evidence-based patient management requires further consideration as more information becomes available. Nurses are powerful patient advocates; they need to stay up-to-date with the rapidly changing information on Zika virus to provide the best care and teaching possible.
References