Zika Virus Disease

A female Aedes aegypti mosquito take flight as she leaves her host’s skin surface.  Photo:  James Gathany
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​About Zika Virus Disease

Zika virus disease (Zika) is a disease caused by the Zika virus, which is spread to people primarily through the bite of an infected Aedes species mosquito. The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected. However, Zika virus infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal brain defects. Once a person has been infected, he or she is likely to be protected from future infections.

Zika virus was first discovered in 1947 and is named after the Zika Forest in Uganda. In 1952, the first human cases of Zika were detected and since then, outbreaks of Zika have been reported in tropical Africa, Southeast Asia, and the Pacific Islands. Zika outbreaks have probably occurred in many locations. Before 2007, at least 14 cases of Zika had been documented, although other cases were likely to have occurred and were not reported. Because the symptoms of Zika are similar to those of many other diseases, many cases may not have been recognized.

​In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infection in Brazil. On February 1, 2016, the World Health Organization (WHO) declared Zika virus a Public Health Emergency of International Concern (PHEIC). Local transmission has been reported in many other countries and territories. Zika virus will likely continue to spread to new areas.
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A female Aedes aegypti mosquito in the process of acquiring a blood meal from her human host. 
​Photo:  James Gathany

Areas with active mosquito-borne transmission of Zika virus

• Prior to 2015, Zika virus outbreaks occurred in areas of Africa, Southeast Asia, and the Pacific Islands.
• In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infections in Brazil.
• Currently, outbreaks are occurring in many countries and territories.
• Zika virus will continue to spread and it will be difficult to determine how and where the virus will spread over time.

US Territories*

• Local mosquito-borne transmission of Zika virus has been reported in the Commonwealth of Puerto Rico, the US Virgin Islands, and American Samoa.

*Territories of the United States are sub-national administrative divisions overseen by the US federal government.
US States

• No local mosquito-borne Zika virus disease cases have been reported in US states, but there have been travel-associated cases.
• With the recent outbreaks, the number of Zika cases among travelers visiting or returning to the United States will likely increase.
• These imported cases could result in local spread of the virus in some areas of the United States.

Americas

• Aruba
• Barbados
• Belize
• Bolivia
• Bonaire
• Brazil
• Colombia
• Commonwealth of Puerto Rico, US territory
• Costa Rica
• Cuba
• Curacao
• Dominica

• Dominican Republic
• Ecuador
• El Salvador
• French Guiana
• Guadeloupe
• Guatemala
• Guyana
• Haiti
• Honduras
• Jamaica
• Martinique
• Mexico
• Nicaragua

• Panama
• Paraguay
• Peru
• Saint Barthélemy
• Saint Lucia
• Saint Martin
• Saint Vincent and the Grenadines
• Sint Maarten
• Suriname
• Trinidad and Tobago
• U.S. Virgin Islands
• Venezuela

 
Oceania/Pacific Islands

• American Samoa
• Fiji
• Kosrae, Federated States of Micronesia
• Marshall Islands
• New Caledonia
• Papua New Guinea
• Samoa
• Tonga

 
Africa

• Cape Verde

Symptoms

• Most people infected with Zika virus won’t even know they have the disease because they won’t have symptoms. The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.
• See your doctor or other healthcare provider if you are pregnant and develop a fever, rash, joint pain, or red eyes within 2 weeks after traveling to a place where Zika has been reported. Be sure to tell your doctor or other healthcare provider where you traveled.
• The illness is usually mild with symptoms lasting for several days to a week.
• People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected.
• Zika virus usually remains in the blood of an infected person for about a week but it can be found longer in some people.
• Once a person has been infected, he or she is likely to be protected from future infections.

Diagnosis

• The symptoms of Zika are similar to those of dengue and chikungunya, diseases spread through the same mosquitoes that transmit Zika.
• See your doctor or other healthcare provider if you develop the symptoms described above and have visited an area where Zika is found.
• If you have recently traveled, tell your doctor or other healthcare provider when and where you traveled.
• Your doctor or other healthcare provider may order blood tests to look for Zika or other similar viruses like dengue or chikungunya.

Treatment

• There is no vaccine to prevent or medicine to treat Zika virus.
• Treat the symptoms:
  • Get plenty of rest.
  • Drink fluids to prevent dehydration.
  • Take medicine such as acetaminophen (Tylenol®) or paracetamol to reduce fever and pain.
  • Do not take aspirin and other non-steroidal anti-inflammatory drugs (NSAIDS) until dengue can be ruled out to reduce the risk of bleeding.
  • If you are taking medicine for another medical condition, talk to your doctor or other healthcare provider before taking additional medication.
• If you have Zika, prevent mosquito bites for the first week of your illness.
  • During the first week of infection, Zika virus can be found in the blood and passed from an infected person to a mosquito through mosquito bites.
  • An infected mosquito can then spread the virus to other people.

For Healthcare Providers

Clinical Guidance

Pregnant Women and Women of Reproductive Age

• UPDATE: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure – United States, 2016 (March 25, 2016)
• Interim Guidelines for Health Care Providers Caring for Pregnant Women and Women of Reproductive Age with Possible Zika Virus Exposure – United States, 2016 (Feb. 5, 2016)
• Interim Guidelines for Pregnant Women During a Zika Virus Outbreak—United States, 2016 (Jan. 22, 2016)
• Questions and Answers for Healthcare Providers Caring for Pregnant Women and Women of Reproductive Age with Possible Zika Virus Exposure

Infants and Children

• UPDATE: Interim Guidelines for Healthcare Providers Caring for Infants and Children with Possible Zika Virus Infection – United States, February 2016 (Feb. 19, 2016)
• Interim Guidelines for the Evaluation and Testing of Infants with Possible Congenital Zika Virus Infection – United States, 2016 (Jan. 29, 2016)
• Questions and Answers for Healthcare Providers Caring for Infants and Children with Possible Zika Virus Infection

Sexual Transmission

• UPDATE: Interim Guidance for Prevention of Sexual Transmission of Zika Virus – United States, 2016 (March 25, 2016)
• Interim Guidelines for Prevention of Sexual Transmission of Zika Virus – United States, 2016 (Feb. 12, 2016)

 
Clinical Evaluation & Disease

Modes of Transmission

Zika virus is a single-stranded RNA virus of the Flaviviridae family, genus Flavivirus. Zika virus is transmitted to humans primarily through the bite of an infected Aedes species mosquito. The mosquito vectors typically breed in domestic water-holding containers; they are aggressive daytime biters and feed both indoors and outdoors near dwellings. Nonhuman and human primates are likely the main reservoirs of the virus, and anthroponotic (human-to-vector-to-human) transmission occurs during outbreaks.
Perinatal, in utero, and possible sexual and transfusion transmission events have also been reported. Zika virus RNA has been identified in asymptomatic blood donors during an ongoing outbreak.

Clinical Signs & Symptoms

Most people infected with Zika virus are asymptomatic. Characteristic clinical findings are acute onset of fever with maculopapular rash, arthralgia, or conjunctivitis. Other commonly reported symptoms include myalgia and headache. Clinical illness is usually mild with symptoms lasting for several days to a week. Severe disease requiring hospitalization is uncommon and case fatality is low. However, there have been cases of Guillain-Barre syndrome reported in patients following suspected Zika virus infection. Recently, CDC concluded that Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects. Due to concerns of microcephaly caused by maternal Zika virus infection, fetuses and infants of women infected with Zika virus during pregnancy should be evaluated for possible congenital infection and neurologic abnormalities.

Diagnosis & Reporting

Based on the typical clinical features, the differential diagnosis for Zika virus infection is broad. In addition to dengue, other considerations include leptospirosis, malaria, rickettsia, group A streptococcus, rubella, measles, and parvovirus, enterovirus, adenovirus, and alphavirus infections (e.g., Chikungunya, Mayaro, Ross River, Barmah Forest, O’nyong-nyong, and Sindbis viruses).

Preliminary diagnosis is based on the patient’s clinical features, places and dates of travel, and activities. Laboratory diagnosis is generally accomplished by testing serum or plasma to detect virus, viral nucleic acid, or virus-specific immunoglobulin M and neutralizing antibodies. 

As an arboviral disease, Zika virus is a nationally notifiable condition. Healthcare providers are encouraged to report suspected cases to their state or local health departments to facilitate diagnosis and mitigate the risk of local transmission. State or local health departments are encouraged to report laboratory-confirmed cases to CDC through ArboNET, the national surveillance system for arboviral disease..

Treatment

No specific antiviral treatment is available for Zika virus disease. Treatment is generally supportive and can include rest, fluids, and use of analgesics and antipyretics. Because of similar geographic distribution and symptoms, patients with suspected Zika virus infections also should be evaluated and managed for possible dengue or chikungunya virus infection. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided until dengue can be ruled out to reduce the risk of hemorrhage. People infected with Zika, chikungunya, or dengue virus should be protected from further mosquito exposure during the first few days of illness to prevent other mosquitoes from becoming infected and reduce the risk of local transmission.

Diagnostic Testing

During the first week after onset of symptoms, Zika virus disease can often be diagnosed by performing reverse transcriptase-polymerase chain reaction (RT-PCR) on serum. Virus-specific IgM and neutralizing antibodies typically develop toward the end of the first week of illness; cross-reaction with related flaviviruses (e.g., dengue and yellow fever viruses) is common and may be difficult to discern. Plaque-reduction neutralization testing can be performed to measure virus-specific neutralizing antibodies and discriminate between cross-reacting antibodies in primary flavivirus infections.

Source:  Centers for Disease Control and Prevention