Zika virus (ZIKV) is a flavivirus related to yellow fever, dengue, West Nile, and Japanese encephalitis viruses.
ZIKV has been isolated from Ae. africanus, Ae. apicoargenteus, Ae. luteocephalus, Ae. aegypti, Ae vitattus, and Ae. furcifer mosquitoes
Zika virus was first discovered in 1947 in the Zika Forest, Uganda, when a Rhesus monkey, placed in a cage to study Yellow Fever developed a febrile illness that was transmitted by innoculation into mice. The Zika Virus was discovered.
In 1948, Zika virus was found in the Aedes Africanus mosquito in the Zika Forest.
In 1968, the virus was found in humans in Nigeria causing a febrile illness. Also in 1971-1975 as well.
Later the virus was found to cause illness in various other parts of Africa and asia, including India, Malaysia, Philippines, and Vietnam.
Then the virus was found to exist in the Aedes aegyptii mosquito.
The Yap island infection in 2007 was the first time infection had spread outside of Asia and Africa.
The disease went on to French Polynesia in 2013 and the Cook islands and new Caledonia in 2014
Clusters of infection started to appear in Brazil in 2014 and 2015. This is because of the mosquito vectors that spread the disease can travel to these areas.
Zirka (ZIKV) virsu causes a self-limited infection in the form of an exanthematous- type rash, low grade fevers, conjunctivitis, and arthralgias. Guillain-Barre syndrome has been associated with this infection (an ascending paralysis). there is much confusion between ZikV and Dengue infection .
(Zika Virus) ZrkV now joins Chikungunya (CIKV) and Dengue Virus (DENV) as global health threats!
Zika virus is believed to be transmitted to humans by infected mosquitoes and has been isolated from Aedes africanus, Aedes luteocephalus, and Aedes aegypti
Until the YAP island/Micronesia outbreak, no transmission of Zika virus had been reported outside of Africa and Asia (2007) in which an outbreak of illness characterized by rash, conjunctivitis, subjective fever, arthralgia, and arthritis occurred on YAP island. Reverse-transcriptase–polymerase-chain-reaction assay determined the source to be Zika virus. Dengue, chikungunya, o’nyongnyong, Ross River, Barmah Forest, and Sindbis viruses were all NEGATIVE in this study.
The Federated States of Micronesia is an archipelago nation located northeast of Papua New Guinea. Yap State is the westernmost of the four states of the country. In Yap cases were defined by fhaving generalized macular or papular rash, arthritis or arthralgia, or nonpurulent conjunctivitis. Acute phase studies were taken 10 days after symptoms and convalescent titers were taken at Day 14. In this Zika virus outbreak, approximately three quarters of Yap residents were infected with Zika virus, and we estimated that more than 900 people had illness attributable to Zika virus infection. It was a mild illness. It appeared that Aedes hensilli was a vector of Zika virus transmission in Yap. More than 73% of Yap islanders were found to have had infection after the age of 3.
The attack rates of Zika virus disease detected by surveillance were higher among females than males and among older persons than younger persons. These discrepancies may be because of differences in health care–seeking behavior for this relatively mild illness.
In the NEJM article regarding the Zika infection on Yap: “The accessibility of air travel and the abundance of mosquito vectors of flavivirus in the Pacific region raise concern for the spread of Zika virus to other islands in Oceania and even to the Americas.” This was in 2007. Also they ended the article with : “The emergence of Zika virus as an important human pathogen on Yap in 2007 underscores the ease with which exotic pathogens are transported between continents and the need for clinical vigilance and strong epidemiologic and laboratory surveillance systems to detect the spread of infectious diseases”
So as a summary, ZikV, ChickV, and DenV cause an exanthemotous illness with a generalized rash and fever and all three spread by the same Aedes mosquito species. It is hard to distinguish between the illnesses. The effect of the concurrent outbreaks caused by these three different arboviruses is unknown.
Fever and arthralgias are more common in Dengue and ChikV infections whereas Guillan Barre episodes are more associated with Zika infection.
The first well-documented report of human ZIKV disease was in 1964 when Simpson described his own occupationally acquired ZIKV illness at age 28 (27). It began with mild headache. The next day, a maculopapular rash covered his face, neck, trunk, and upper arms, and spread to his palms and soles. Transient fever, malaise, and back pain developed. By the evening of the second day of illness he was afebrile, the rash was fading, and he felt better. By day three, he felt well and had only the rash, which disappeared over the next 2 days. ZIKV was isolated from serum collected while he was febrile. . Other manifestations included anorexia, diarrhea, constipation, abdominal pain, and dizziness. Yap Island infection was characterized by rash, conjunctivitis, and arthralgia.
Diagnostic tests for ZIKV infection include PCR tests on acute-phase serum samples, which detect viral RNA, and other tests to detect specific antibody against ZIKV in serum. An ELISA has been developed at the Arboviral Diagnostic and Reference Laboratory of the Centers for Disease Control and Prevention (Atlanta, GA, USA) to detect immunoglobulin (Ig) M to ZIKV. IgM was detectable as early as 3 days after onset of illness. In the samples from Yap Island, cross-reactive results in sera from convalescent-phase patients occurred more frequently among patients with evidence of previous flavivirus infections than among those with apparent primary ZIKV infections . Cross-reactivity was more frequently noted with dengue virus than with yellow fever, Japanese encephalitis, Murray Valley encephalitis, or West Nile viruses. Zika Virus Outside Africa <Link
ZIKV illness to date has been mild and self-limited, but before West Nile virus caused large outbreaks of neuro-invasive disease in Romania and in North America, it was also considered to be a relatively innocuous pathogen.
In the early 2015, records of patients presenting a “dengue-like syndrome” appeared in the public health service in the city of Natal (05°47’42”S 35°12’32”O), state of Rio Grande do Norte, Brazil. A physician specialist in infectious disease evaluated the patients and the clinical signs and symptoms and laboratory findings indicated a non-DENV and non-Chikungunya virus (CHIKV) infection. Symptoms included arthralgia, oedema of extremities, mild fever, maculopapular rashes frequently pruritic, headaches, retroorbital pain, no purulent conjunctivitis, vertigo, myalgia and digestive disorder. http://www.ncbi.nlm.nih.gov/pmc/articles/PFirst report of autochthonous transmission of Zika virus in Brazil
In Brazil’s caese: The most commonly reported symptoms were maculopapular rash (100%) and pain, with pain lasting 2-15 days. Headaches, myalgias, and retro-orbital pain was common, and joint pains included the hands , ankle, elbow , knee, wrist, and foot. Periarticular swelling occurred, fever (around 39ºC), and submandibular or cervical lymphadenopathy in some. Most had normal levels of leukocytes and neutrophils and platelets were normal in all of them.
As of January 23 – the CDC recommends that pregnant women not travel to Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela and Puerto Rico. Zika has been found in Bolivia, Brazil., COlombia, Ecuador, French Guiana, Guyana, Suriname, Venezuela, and Paraguay. In the Caribbean, Barbados, Guadeloupe, Haiti, Martinique, and Saint Martin have Zika Virus present. Also Mexico, Puerto Rico, Honduras, Panama, and Guatemala have Zika virus present as well.
Microcephaly has been linked to this infection as a result of infection during pregnancy. Obviously microcephaly results in developmental delay (Mental Retardation.)
In El Salvador, cases of a demyelinating condition called Guillian Barre syndrome has occurred in association with the Zika infection.
El Salvador has recommended a Two year halt on pregnancies and Jamaica recommends a 6-12 month wait for women to become pregnant. Obviously, these recommendations will be challenging to follow.
For those who get pregnant in high risk areas, ultrasound and amniocentesis ( a needle is used to collect amniotic fluid for analysis) is performed and tested for Zika virus. If positive, options are discussed.
Prevention of the disease if travel is a necessity includes wearing long sleeved shirts and pants, using insect repellents that have DEET, Picardin, oil of lemon eucalyptus (OLE), or IR3535. DEET can be used on infants 2 months or older and pregnant women can safely use EPA-registered insect repellents.
- Amniocentesis, in which a needle is used to retrieve a sample of amniotic fluid from the uterus, is recommended as a follow-up in women who have had a blood test result that is positive for Zika virus or who have had an abnormal finding on an ultrasound
- Of note, in the U.S. it may be possible for infected travelers to get bitten by specific mosquitos that then can be infected and transmit to others. See Evidence for an Overwintering Population of Aedes aegypti in Capitol Hill Neighborhood, Washington, DC
- Zika Virus in Cape Verde October 2015 CDC <–Local trasmissions noted by CDC in Cape Verde and Samoa below.
- Zika Virus in Samoa – January 22 2016
- For up to date CDC travel notices check : CDC travel notices <–CDC travel notices
- CDC Zika Website <Zika CDC Website Link
- American Society of Tropical medicine and Hygiene
- PLOS ONE_ Clinical Manifestations and Case Management of Ebola Haemorrhagic Fever Caused by a Newly Identified Virus Strain, Bundibugyo, Uganda, 2007–2008
- hDetection of Entebbe Bat Virus After 54 Years
- Serological Investigation of Heartland Virus (Bunyaviridae: Phlebovirus) Exposure in Wild and Domestic Animals Adjacent to Human Case Sites in Missouri 2012–2013
- UK reports Zika cases as El Salvador urged to lift abortion ban over virus risk <–January 24, 2016
- British Zika Website British Zika website
- AMA Zika Resource Center – February 2016
- Zika Map of infections
- Science Magazine Zika Questions and Answers: Zika – Science Magazine
- January 28 CNN Zika report
- Zika – and microcephaly January 2016
- Zika CDC site
Symptomatic management with supportive care is indicated for acute cases. Prevention is achieved by vector control and insect bite precautions. Aedes spp. is adapted for indoor and daytime biting in urban areas. They are known to breed in aquatic environments such as small puddles, open water storage containers, and plants that hold water between the leaves and stems. Insect bite precautions (during early morning and late afternoon peak biting times) and vector control should be tailored to known epidemiology.
This report illustrates the potential for explosive simultaneous outbreaks of ZIKV, CHIKV, and DENV in the Western Hemisphere and the increasing public health effects of Aedes spp. mosquitoes as vectors. The apparent increase in reports of Guillain-Barré syndrome during the outbreak deserves further investigation to elucidate whether this syndrome is associated with ZIKV infection.
Identification of ZIKV, CHIKV and DENV as etiologic agents of acute exanthematous illness suggests that these 3 Aedes spp. mosquito-transmitted viruses were co-circulating in Salvador and highlights the challenge in clinically differentiating these infections during outbreaks. In Brazil, that ZIKV sequences obtained belonged to the Asian lineage and showed 99% identity with a sequence from a ZIKV isolate from French Polynesia (KJ776791) .
Update: January 20, 2016
Hawaii baby born with small head had prior Zika infection A child born in the past few weeks in Hawaii had microcephaly ( a small head) and the mother had lived in Brazil in 2015. Both were positive for prior Zika infection. Currently, cases in Brazil increased to 3,500, and 46 babies have died. The CDC gave recommendations not to travel to Brazil if pregnant or if wishing to get pregnant due to concerns over Zika Virus:
CDC has issued a travel alert (Level 2-Practice Enhanced Precautions) for people traveling to regions and certain countries where Zika virus transmission is ongoing: Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, and the Commonwealth of Puerto Rico.
This alert follows reports in Brazil of microcephaly and other poor pregnancy outcomes in babies of mothers who were infected with Zika virus while pregnant. However, additional studies are needed to further characterize this relationship. More studies are planned to learn more about the risks of Zika virus infection during pregnancy.
Until more is known, and out of an abundance of caution, CDC recommends special precautions for pregnant women and women trying to become pregnant:
- Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing. Pregnant women who must travel to one of these areas should talk to their doctor or other healthcare provider first and strictly follow steps to avoid mosquito bites during the trip.
- Women trying to become pregnant should consult with their healthcare provider before traveling to these areas and strictly follow steps to prevent mosquito bites during the trip.
- CDC Travel Website: CDC Travel information
- Jama Zika article February 1 <<
As a reiteration, Zika virus is a flavivirus that is related to Japanese encephalitis virus, West Nile, Dengue, and yellow fever. It originated in the Zika Forest in Uganda and was first found in 1947 in a rhesus monkey.
As of February 1, 2016 the virus has spread in Africa, Southeast Asia, the pacific Islands, and the Americas.
Zika is likely to spread to the United States since the mosquito vector, Aedes, an aggressive daytime biter, is present in the US as well. Obviously international travelers will promulgate the spread of the disease.
The symptoms of infection are fever, rash, muscle and joint pains with conjunctivitis (pink eye) primarily, but there is associations with microcephaly and Guillian Barre syndrome (GBS) as well. GBS is a neurological syndrome of weakness and paralysis.
Brazil has had 4000 cases of microcephaly in 2015 which i 20 times higher than the year before with evidence of viral infection in the mother’s of these patients.
Infections have been found in travelers in Hawaii, Florida, Illinois, and Texas. All were international travelers.
The primary goal to thwart continued spread and infection is vector control. Physical removal of standing water and adding fish to areas with water so as to eat larvae are part of a solution, Insecticides are beneficial as well. Also being tried is the release of sterile male mosquitoes.
The Pan American Health Organization (PAHO) has been issuing updates for increased surveillance for Zika, including immunological effects of the virus as well as congenital effects from infection.
Travel advisories are in effect from the CDC primarily for pregnant women in which they suggest postponing travel if pregnant if one is travelling to Zika-affected areas.
There are licensed vaccines for yellow fever, Japanese encephalitis, and dengue fever currently, but non e for Zika. NIH and Brazilian agencies are currently working on this.
80 % of Zika infections are asymptomatic and most are self-limited. It is hard to test for the virus due to cross-reactivity with other flaviviruses. The CDC is able to test amniotic fluid and serum for the virus currently.
NEJM Zika in the US NEJM article re: zika in the US
Interim Guidelines for Pregnant Women During a Zika Virus Outbreak — United States, 2016 _ MMWR – Guidelines from CDC for pregnant women 2016
Ebola epidemic – JAMA 2014 Ebola epidemic in 2014
<Blog from NIH – video
Notes from NIH blog:
According to the researchers’ calculations, about 200 million Americans—more than 60 percent of the population—reside in areas of the United States that might be conducive to the spread of Zika virus during warmer months through biting mosquitoes, including areas along the East and West Coasts and much of the Midwest. In addition, another 22.7 million people live in humid, subtropical parts of the country that might support the spread of Zika virus all year round, including southern Texas and Florida. Already, there are reports of local spread of the virus within Puerto Rico and of travelers returning to the U.S. with the Zika infection.
In November, health authorities in French Polynesia also reported an unusual increase of central nervous system malformations in fetuses and infants that seemed to coincide with the Zika outbreak there. And, last week, came news reports of the first child born in the U.S. with microcephaly possibly linked to Zika. The child’s mother had lived in Brazil during her pregnancy before moving to Oahu, Hawaii . As an additional concern, there are reports in French Polynesia and Brazil of a possible connection between Zika infection and Guillain-Barré syndrome, a mysterious condition in which the immune system attacks part of the peripheral nervous system 
Zika virus infection can be spread by yellow fever mosquitoes (Aedes aegypti), and experimental evidence suggests the virus also can be transmitted by Asian tiger mosquitoes (Aedes albopictus).Aedes mosquitoes—already known for transmitting other viral illnesses, such as dengue and chikungunya—have a wide and expanding global distribution, including in the United States.