Expert commentaries on the Zika virus
Experts, selected primarily from our pool of authors, have written overviews that provide useful information to students, researchers, health care professionals and other scientifically minded individuals. Coming from a broad spectrum of disciplines, these experts write about how their particular field is involved in the scientific investigations to contain the virus and care for patients. Each overview offers a selection of freely available content as chosen by the author.
Further content will be posted as it becomes available.
March of Dimes and NORC Poll Shows Gaps in Americans’ Knowledge of Zika Virus
As the number of reported cases of the Zika virus rises in the United States, many Americans, including some men and women most at risk, do not understand details about the virus such as how it is transmitted or its health consequences. However, there is growing concern among the public about Zika, and many Americans are taking steps to protect themselves from the virus, according to our recent nationally representative survey conducted by March of Dimes and NORC at the University of Chicago.
The Placenta and Zika
The placenta in maternal-fetal viral transmission and the congenital Zika syndrome:
Hofbauer cells, trophoblast and chorionic villi
The causal relationship between Zika virus infection in pregnancy and the development of intrauterine fetal malformations, including microcephaly, is now well accepted. Analysis of the spectrum of pathologic findings from autopsies of fetuses and infants with congenital Zika virus infection, together with neuroradiology studies, have been of critical importance in defining the central nervous system abnormalities caused by the virus (Schwartz, 2016a; Soares de Oliveira-Szejnfeld et al. 2016).
Zika virus – response by the drug makers
Up until mid-2015, very few of us had ever heard of the condition microcephaly. Reported cases were few and far apart, and certainly never made the headlines. The condition describes an abnormally small head and brain that is caused by genetic abnormalities arising during fetal development. Babies born with the condition are afflicted with several life-long cognitive and neurological disabilities.
The Associated Press-NORC Center research Zika poll
As temperatures start climbing and students start preparing for final exams, many Americans are looking forward to the summer season. For most Americans, the threat of the Zika virus is not interfering with their summer daydreams, according to our recent nationally representative survey conducted by The Associated Press-NORC Center for Public Affairs Research.
Four in ten American adults have heard only a little or nothing at all about the Zika virus. And among those who are aware of the virus, few are very worried about the threat of an outbreak in the U.S. (16 %) or the personal risk of infection (12 %).
Fetal brain damage and Zika virus infection
Following the initial observation of Zika virus infections in Brazil in early 2015, there were reports of an unusual increase in infants born with microcephaly in the state of Pernambuco. In October 2015, Brazil International Health Regulations (IHR) National Focal Point (NFP) confirmed that there were significant increases in the number of infants born with microcephaly in the Brazilian states of Pernambuco, Rio Grande do Norte and Paraiba during 2015 as compared with previous years.
Zika - facts and risks for pregnant women in Europe
The Zika virus is a mosquito-transmitted flavivirus belonging to the Spondweni virus group. It has a single-stranded plus-strand RNA-genome of 10.617 base pairs surrounded by a capsid and envelope (Baronti et al., 2014). An African and an Asian genetic lineage are known. The virus presently circulating in the Americas belongs to the Asian lineage.
Zika virus and the practice of obstetrics
The Zika virus was first discovered in the Zika forest of Uganda in the 1940s. Since its initial isolation, multiple outbreaks have been reported in Africa, Southeast Asia, the Pacific Islands, and most recently, the Americas. Symptoms of Zika in healthy, nonpregnant patients are typically mild and include rash, arthralgia, and conjunctivitis. Fever is an uncommon finding, and most symptomatic infections are self limited, resolving with only supportive care to relieve the symptoms. Further, over 80% of individuals infected with Zika are asymptomatic (CDC, 2016).
The nonspecific and mild nature of previously reported Zika outbreaks has led to a deficiency in research on and advances in diagnostic tests, as well as preventive and therapeutic agents to combat its spread over the last 70 years of its recognition. It was not until 2015, when physicians in Brazil began noticing an alarming increase in the rate of microcephaly in conjunction with a Zika outbreak, that global attention was focused on the illness.
Reflections on Zika virus (ZIKV) and public health
In its natural cycle, ZIKV is transmitted between primates, human or non-human, by the bite of several mosquito species, especially of the genus Aedes (For more information, please see: Zika Virus, 2015). However, evidence of perinatal transmission from mother to child and also by sexual contact has been increasing (For more information, please see: The expanding spectrum of modes of transmission of Zika virus: a global concern, 3 March 2016).
People infected by ZIKV may develop illness characterized by mild fever, rash, conjunctivitis, joint pain, muscle pain and headache. The malaise begins two to seven days after the person is bitten by an infective mosquito or after sexual contact; however, only about 25% of the people infected develop symptoms of the disease. Neurological disorders such as the Guillain-Barré (GB) syndrome may occur, and in pregnancy, the baby may develop microcephaly.
ZIKV was identified in a rhesus monkey in the Zika forest, Uganda (1947), and later was found infecting mosquitoes and humans in Africa and Asia. A spillover of ZIKV beyond the African-Asian region occurred in 2007, reaching Yap Island (Micronesia).
Mosquito vector-virus interactions
Blood is a rich source of proteins, fat and sugar worth dying for. The act of hematophagy, the habit of feeding from blood, offers great risk to arthropods that use blood as their main source of food, as they can be spotted and swatted during their blood-feeding quest. Besides, blood is not an easy meal to take or digest. For instance, arthropods need to escape overheating from meals taken from warm-blooded vertebrate hosts and hemin-induced oxidative stress during hemoglobin metabolism.
Even so, hematophagy is believed to have been acquired as a co-evolution trait 130 million years ago between animals and hematophagous arthropods. Many arthropods are hematophagous, such as ticks (acaridae, Arachnida, 4-pair of legs) and Insecta (3-pair of legs), including lice (pediculidae), fleas (pulidae), bed bugs (cimicidae), kissing bugs (triatomidae), sandflies (psychodidae), blackflies (simulidae) and mosquitoes (culicidae).
Zika virus – short overview of the disease outbreak
Zika virus (ZIKV) is a Flavivirus, which means it is closely related to yellow fever, dengue and West Nile viruses. All of these viruses are transmitted by mosquitoes and are collectively referred to as arboviruses (arbo meaning ARthropod-BOrne). There are two types, or lineages, of Zika virus – the African and the Asian lineages. Recent genetic studies have shown that the one currently causing a panic in South America belongs to the Asian lineage.
ZIKV was incidentally isolated from a caged research (rhesus macaque) monkey in the Zika Forest near Entebbe in Uganda in 1947. Although the virus only recently came to the world’s attention, it has been infecting humans in an equatorial belt across Africa and Asia for more than 50 years. However, in 2014 the first reports emerged of the virus spreading across the Pacific Ocean to French Polynesia and then in 2015 onto Central and South America and the Caribbean.
Sexual transmission of Zika virus
From time to time, the world experiences challenges related to human health. Many of these problems first affect small populations in localized regions of the planet. Depending on the problem’s characteristics, the situation can spread all over the world.
Zika Virus and Host Immunity
Zika virus (ZIKV) is an emerging mosquito-borne member of the Flavivirus genus, which includes dengue (DENV), West Nile (WNV), Yellow fever (YFV) and Japanese encephalitis viruses (JEV). The virus was initially isolated from a rhesus monkey in the Zika Forest of Uganda in 1947 . Since then, it has caused small outbreaks in Africa, Asia and more recently major epidemics in South and Central America [2-5].
Entomological aspects of Aedes aegypti and A. albopictus, vectors of Zika and several other arboviruses
Although several Aedes mosquitoes, mostly of the subgenus Stegomyia, may be infected by Zika, dengue, Chikungunya and yellow fever viruses, Aedes aegypti is their principal vector and is suspect in the transmission of several other infectious agents. The ability of A. aegypti to act as a vector is due to several factors, discussed below.
How Pathology Helps to Understand the Role of Zika Virus During Pregnancy and Fetal Infection
In previous outbreaks and epidemics of emerging infectious diseases, pathology has proven to be a valuable tool for the understanding of how microorganisms can cause disease in a human host (Schwartz, et al. 1995). The microscopic examination of cells and tissues from infected individuals can potentially reveal several important findings.
Animal Models of Zika Virus Infection
Zika virus (ZIKV) is an emerging flavivirus that is transmitted by Aedes mosquitoes and which is currently causing an epidemic in Latin America and the Caribbean . ZIKV historically has been associated with self-limited febrile illness (e.g. fever, rash, mild arthralgia), however, the most recent ZIKV outbreak has been associated with more severe outcomes, including Guillain-Barré syndrome (GBS) .
Of further concern, the emergence of ZIKV in Brazil has coincided with a significant increase in cases of microcephaly, a devastating congenital disorder where fetal brain development is impaired, and a growing body of evidence supports a causal role for ZIKV in the development of birth defects (For more information, please see: Zika virus: a new threat from mosquitoes, 5 March 2016) [3, 4].
Zika and the Priority of Primary Care
As both an epidemiologist and an anthropologist, I engage with great interest in the ecological and social aspects of various types of outbreaks, especially where biology and society intersect (which, of course, is inherent to any outbreak). I write this field overview from the Republic of Costa Rica, a middle-income country in Central America known for its decades-long priorities on health, education, and the lack of a central military.
Insect toxicology and control
Zika is a tropical forest located a few kilometers from Kampala, Uganda's capital. In 1947, an unknown virus was found in the blood of a monkey who lived in this forest. The microorganism was baptized “Zika virus,” and it belongs to the same group as the viruses that cause dengue and chikungunya fever. Like them, Zika is transmitted by Aedes aegypti and other mosquitoes of the genus Aedes. In human beings, Zika virus causes Zika fever, an infectious disease presenting dengue-like symptoms.
Furthermore, it is suspected that there is a relationship between Zika virus infection during pregnancy and birth malformation (microcephaly).
Until a few years ago, Zika virus had been detected only in some countries in Africa, Asia and Oceania. In 2015, the first epidemic in the Western Hemisphere was reported in Brazil. In the following months, the disease spread in the Americas.