Texas Mosquitoes and the Zika Virus: Now Much Worse Than First Thought…

This article by Jerry Cates, first published on 27 April 2016, was last revised on 23 March 2019. © Bugsinthenews Vol. 17:04(01).


Digitally-colorized transmission electron micrograph (TEM) of the Zika virus. The virus particles are blue, and are 40 nm in diameter, with an outer envelope and a dense inner core. Courtesy Cynthia Goldsmith, Centers for Disease Control (CDC)

Digitally-colorized transmission electron micrograph (TEM) of the Zika virus. The virus particles are blue, and are 40 nm in diameter, with an outer envelope and a dense inner core. Courtesy Cynthia Goldsmith, Centers for Disease Control and Prevention (CDC)

The Zika virus, a member of the Flaviviridae family of viruses, is mostly spread by two species of day-active mosquitoes. The virus is closely related to those that cause dengue, yellow fever, Japanese encephalitis, and West Nile fever. Though most Zika infections in humans are either asymptomatic or produce only mild symptoms, affected women who are pregnant may give birth to children with serious birth defects, including microcephaly and other brain abnormalities. A wide range of other complications — in adults, children, and in the fetus   — have recently also been ascribed to infections from this virus, and as time goes on the trend seems to indicate that more adult humans, infected by Zika virus, suffer serious deleterious effects in the long term than we had previously believed.

It is no exaggeration to assert that this new, relatively unknown and little understood scourge represents, today, one of the greatest epidemiological threats facing our nation. All of the geographic area served by EntomoBiotics Inc. is included in the range of the two species of mosquitoes that are its primary vectors. Thus, it is incumbent on us to study and learn as much about it and its vectors as we can. We must then use that knowledge and understanding to find ways to combat it, and bring it under control. This paper represents our first step in the direction of that goal.

Research carried out by investigative microbiologists, dipterists, and pathologists throughout the world is just now beginning to shed light on how serious this virus is, in terms of a threat to the human race worldwide. As evidence mounts that Zika poses unusually deadly risks to developing fetal brains in not only humans but in other mammals as well, and that the risks posed by this virus extend far beyond developing fetuses to infant, adolescent, and adult mammals — in many ways not yet fully understood — medical and microbiological communities are becoming more and more alarmed. On 12 May 2016 one scientist at Harvard University, Dr. Amir Attaran, writing in the Harvard Public Health Review, cautioned that the Olympic Games — scheduled from 3-21 August 2016 in Rio de Janeiro, Brazil, could help to speed up the spread of the virus. As a result, Attaran suggested that the Games might best be hosted by another city in Brazil where the illness is less of a threat.

While Brazil’s Zika inevitably will spread globally, given enough time – viruses always do – it helps nobody,” Attaran said, “to speed that up. In particular, it cannot possibly help when an estimated 500,000 foreign tourists flock into Rio for the Games, potentially becoming infected, and returning to their homes where both local Aedes mosquitoes and sexual transmission can establish new outbreaks.


EntomoBiotics OviTrap

EntomoBiotics initial Aedes Mosquito OviTrap. This trap, which has since undergone significant improvement, is similar to a design patented by the U.S. Centers for Disease Control and Prevention (CDC), using a 5-gallon black plastic bucket, a length of unperforated drain pipe, die-cut sections of acrylic plastic sheeting, a cylinder whose interior is coated with butylene (non-drying) glue, an ovicup filled with wet hydrogel, stainless steel screening to prevent adult mosquitoes from exiting the infusion chamber, and an infusion chamber filled with water infused with decaying hay to produce attractants to Aedes mosquitoes. This station has now been replaced by the In2Care mosquito trap…

The EntomoBiotics Zika Virus Research Project: The lead investigator on this project, Jerry Cates, has been a student of mosquito biology since 1963, when he began documenting the strategies used by natives in Southeast Asia to avoid bites from Anopheline mosquitoes and reduce malaria infections. Since that time he has conducted a number of in-depth studies on mosquito anatomy, reproduction, and behavior, focusing on their preferred habitats and reduced-risk/non-toxic methods of mosquito control.

It is our privilege, today, to service a number of medically-related facilities throughout the state of Texas, all of whom are subject to mosquito infestations during certain times of the year. EntomoBiotics Inc. has never wavered in our commitment to finding bettter ways to control the mosquito populations that affect those who work at, live in, and visit such facilities.

Our current research into Aedes mosquito biology and Zika virus transmission is now, as in times past, oriented toward finding effective methods, products, and materials that may be used to reduce or eliminate noxious pest populations at such sites. This research — which is a crucial part of the EntomoBiotics War on Mosquitoes — is being funded by EntomoBiotics Inc. and the Megatherium Society, the not-for-profit biological research arm of EntomoBiotics Inc. that Jerry founded for just this kind of project. The medically-related facilities where the products of this research will be tested and documented will not be charged extra for the installation of mosquito abatement/elimination devices or the documentation involved with this project. Latest test results suggest the devices used in this project will not require the use of toxic materials of any kind, and need to be serviced no more often than once a month to ensure the devices are kept at peak operating efficiency.


Zika Transmission via Mosquito Bites

The primary route of infection for Zika virus disease (Zika) is through the bite of an infected mosquito, but the disease can also be transmitted secondarily through unprotected sex. With respect to the primary route of transmission, only mosquitoes in the genus Aedes are known to transmit the disease.

Aedes albopictus

Asian Tiger Mosquito (Aedes albopictus). Courtesy James Gathany, of the U.S. Centers of Disease Control and Prevention (CDC). Both Aedes albopictus and Aedes aegypti are characterized by the presence of alternating pale and dark sections in their legs and body, giving them a striped appearance; Ae. albopictus has a single longitudinal stripe on its dorsal thorax, while Ae. aegypti has a more complex marking in this region resembling a lyre. it is an epidemiologically important vector for the transmission of a variety of viral pathogens, including yellow fever, Zika, dengue fever, and Chikungunya fever. It is also known to transmit several filarial nematodes, including Dirofilaria immitis.

Persons infected by the Zika virus most commonly experience fever, rash, painful joints, and conjunctivitis (reddening of the conjunctiva surrounding the eyes). Most of the time these symptoms are mild, last for several days to a week, and are not severe enough to lead infected individuals to seek medical care. It is believed that once a person is infected, the disease remains viable in the infected individual’s blood stream for as long as three weeks. During that interval, if the infected individual is bitten by a mosquito, that mosquito may become infected with the Zika virus and may, subsequently, transmit the disease to other individuals through its bites.

Complications from Zika Virus Infections

Deaths caused by Zika virus disease are rare, though in April 2016 a 70-year-old man in Puerto Rico was reported to have died as a result of a Zika infection. Because death is so rare and symptoms are often absent or extremely mild, the rate of infection is likely underreported. Despite these facts — that the infected individual may experience no symptoms, or only mild discomfort — Zika virus infection carries high risks with some individuals. Infections during pregnancy, for example, can pass from the mother to the baby in the womb, where it may cause a serious birth defect called microcephaly, as well as other severe fetal brain defects.

In adults, Zika has been associated with a number of important complications, including Guillain-Barré syndrome (GBS), an uncommon sickness of the nervous system in which the infected person’s immune system damages nerve cells, leading to muscle weakness and in some cases paralysis. GBS symptoms include weakness of the arms and legs, usually of the the same degree on both sides of the body. Sometimes muscles of the face that control eye movement or swallowing may also become involved. In serious cases this muscle weakness may affect breathing to the point that a breathing tube is required to assist in respiration. GBS symptoms last a few weeks to several months. Most victims recover fully, but some incur permanent damage, and 5% (1 in 20) suffer fatal complications. Thus, GBS is not a trivial complication of Zika.

Sexual Transmission of Zika

Infected human males are now known to be able to transmit the disease to sexual partners through their semen, whether the infected male has Zika symptoms or not. In some cases, transmission of the disease occurred after an infected, symptomatic male’s symptoms had ceased. This confirms suspicions that the virus is able to survive in semen for longer periods than it can survive in the blood stream.

It is not believed that human females can transmit Zika to another person via bodily fluids. By contrast, tests performed on semen collected from a male infected as long as 62 days previously remained positive for at least traces of the Zika virus. It was not determined if the virus traces detected in the test were live and viable. However, erring on the side of caution, it is possible that anyone who has unprotected sex with a male who may have become exposed to Zika in the past 120 days may become infected with Zika as a result. Additional testing is expected to soon shed light on just how long Zika remains viable in various human body fluids following infection.

Zika virus structure

Like other flaviviruses, Zika virus is enveloped in a capsid, is icosahedral (i.e., is a convex polyhedron with 20 faces, 30 edges and 12 vertices) in form, and has a nonsegmented, single-stranded, positive-sense RNA genome. Most closely related to the Spondweni virus, Zika is one of two viruses assigned to the Spondweni virus clade.

Unlike negative-sense RNA genomes — that are unable to be translated into viral proteins directly — positive-sense RNA genomes can undergo direct translation into viral proteins without requiring intermediaries. As with the similarly sized West Nile virus, Zika’s RNA genome encodes seven nonstructural proteins and three structural proteins. The structural proteins form the capsid that encapsulates the virus. The replicated RNA strand is held within a nucleocapsid, and the capsid itself is contained within a membrane derived from the host.

African and Asian Lineages

Two lineages of Zika have been identified. The first, an African lineage, is typified by the Zika genome that was discovered in 1947; the second is an Asian lineage, which circulated in French Polynesia during an outbreak there in 2013-14, and that differs in important ways from the earlier African lineage.

The genome of the virus now circulating in the Americas is only 89% identical to the African genotype, but has a greater similarity to the Asian lineage genotype collected in French Polynesia during the 2013-14 outbreak.

How Zika Evolved

The original vertebrate hosts of the Zika virus are believed to be monkeys, which in their natural settings became part of an enzootic (i.e., a disease that regularly affects animals in a particular district or at a particular season) cycle that, in this case, is best described as mosquito-to-monkey-to-mosquito. Only rarely, at first, would the virus be transmitted to humans, even in locales where the mosquito-monkey-mosquito enzootic cycle was robust.

Mosquito Vectors of the Zika Virus

Two species of mosquitoes, both in the Culicinae family and the genus Aedes, are known to transmit the Zika virus. Both species — Aedes aegypti and Aedes albopictus — are presently found in the United States, though their distribution is concentrated in the southeastern U.S. states of the eastern seaboard and the gulf coast (including all of Texas).

The EntomoBiotics Zika Research Project: Non-toxic Solutions for Mosquito Control.

Due to the imminent threat to humans from the Zika virus, amid reports that the virus is now present in Texas and other parts of the U.S., we are re-prioritizing all our research projects, placing Zika research at the top of the lit. For the next few months we will concentrate on collecting specimens of Aedes mosquitoes, studying their biology, and testing various control measures — particularly those that do not involve the use of toxicant-based control methods. Our object is to deploy mosquito abatement devices, formulate  additional programs to eradicate Aedes mosquitoes, and develop cleansers capable of mitigating the risks they and the Zika virus pose to persons within our service area (all of Texas).

Over the past 36 years we’ve studied a number of methods used to control spiders, mosquitoes, and lake midges. Those methods and the products they use have been all over the board. In sum, we’ve not been pleased with any of the programs that concentrate on toxicant-pesticide-based solutions. All require the continuous use of indiscriminate, broad-band pesticides that kill as many beneficial insects as the genuine pests they target. That’s not at all good, because the beneficial organisms in our midst tend to do a better job of keeping pests under control than anything we — as pest management providers — can ever do. When regular use of indiscriminate broad-band pesticides decimate beneficial organisms, larger amounts of even more toxic pesticides must be used, in a never-ending spiral that goes from bad to worse. This is because toxicant-based pest control invariably selects for, and encourages the development of resistant strains. Naturally, over time those resistant strains become dominant. When that happens — and it invariably does — stronger, more toxic pesticides have to be applied to bring them under control.

Thats seemingly never-ending spiral must be brought to a halt. The last thing we want or need for mosquito control in a medically-based environment — where people are already suffering from illnesses, and are recuperating from medical procedures such as surgery and chemo-therapy — is a toxic pesticide that might make their conditions worse. Consequently, our research into ways to combat mosquitoes and the arboviruses they carry has concentrated on non-toxic methods of control. Fortunately, a raft of research projects, focused precisely on those kinds of solutions, have been carried out by a number of researchers all over the world. Some of them have produced extremely promising results.

Recent Developments in Non-Toxic Mosquito Control Devices

The U.S. Centers for Disease Control and Prevention (CDC) has financed a number of research projects targeting mosquito control. The object, from the start, was to find a solution that works as well or better than DDT, the “miracle” mosquito control toxicant that — during WW-II and in the next two decades that followed — promised to eradicate malaria from the earth. However, that promised eradication didn’t happen.

Many believe DDT only failed because it was banned for agricultural use in the U.S. in 1972, and banned almost everywhere for most other uses during the 1980’s. On the other hand, it is indisputable that, as early as the late 1940’s, mosquitoes worldwide had begun to develop resistant strains that thrived where DDT was being used. By the 1970’s there were no species of mosquitoes that were not at least somewhat resistant to DDT. The result? More and more DDT had to be applied to achieve mosquito control, and as DDT usage increased, so did the development of mosquito resistance. Had its use been continued, it is almost certain that the utility of DDT to combat mosquitoes would have diminished to near zero by the late 1990’s.

For many years, the quest for a non-toxic solution to mosquito control focused on the use of synthetic pheromones and similar kinds of lures that had to be manufactured by chemists using proprietary processes and specialized equipment. In more recent times, however, it has been discovered that natural processes, such as those that accompany the fermentation of weed clumps in swampy environs, produce volatiles that lure mosquitoes to their locations. Those processes can be duplicated in relatively small devices placed around homes and businesses. When combined with other elements, such devices have proven capable of inducing mosquitoes to lay their eggs in places where they cannot hatch (or, if some do hatch, where they cannot then develop into mature mosquitoes), and — for those that further contain sticky surfaces — that entrap the mosquitoes and prevent them from exiting the device.

Throughout 2026-2017, we at EntomoBiotics Inc. studied all the devices described in the literature, and tested versions of the most promising ones on that list. None are on the market, so we had to make each of them from scratch using available materials obtainable locally. We put enough of them together to enable us to place several at each of the medically-related facilities we serviced (after obtaining express permission from the administrators of each facility), beginning in May, 2016. We then solicited the staff at those facilities to keep us informed on how effective those devices were at keeping mosquito populations at their locations in check.

In the Coming Days, Weeks, Months, and Years…

Many of these devices were deployed throughout Texas by the end of May, 2016, and additional numbers were deployed in each of the months of June, July, and August. We built them to last, and each one continued to work well for several years. They were also built so that they could be modified as improvements in design are called for. In the months and years that followed, the results of this testing program were tabulated.

Residential Deployments of the EntomoBiotics Mosquito Ovitrap

Beginning in May, 2016, many of our residential clients requested that we install the mosquito ovitraps at their homes. We did so, after first testing them at a number of residential sites to determine if they would perform adequately enough to provide effective mosquito control at individual residences. We proved from those test sites that the ovitraps would significantly reduce the mosquito populations at the residences where they were deployed. Mosquitoes would, however, continue to drift into those yards from surrounding areas. If nothing was done to mitigate the threat posed by those drifters, the ovitraps alone would not suffice.

We addressed this by making available to our residential clients the aqueous, oil-based, dust-based, and granular cleansers we make. These non-toxic, herb & spice based cleansers create an environment, wherever they are applied, that is habitat neutral. That is, the environment cleansed by them is devoid of attractant contaminants, and thus ceases to lure or entice animals or insects that are foraging for food. With respect to mosquitoes, within such an environment they are unable to find anything worthy of biting, so they go elsewhere. Spraying oneself lightly — on skin and clothing — with our aqueous HabitatBiotics™ V512 herbal cleanser, then spraying the same product on foliage, chairs, pergola columns, etc., typically causes the mosquitoes that had been foraging in the area to depart. A single spraying usually lasts four hours or more, after which time a fresh cleansing spray renews the effect. When this is combined with the use of our mineral oil HabitatBiotics™ M92 cleansing spray — which can be used on inanimate objects, but not on live foliage — the cleansing effect lasts even longer. Clients who regularly use our non-toxic, herb and spice based granular cleanser, HabitatBiotics™ G1440, to cleanse the perimeters of their homes and yards, experience even more dramatic results.

Our On-Going Quest for Improvement and Innovation…

This project continued through 2017, when the CDC designed ovitraps were replaced by the In2Care mosquito traps. The In2Care mosquito trap was deployed in selected locations throughout 2018.

What we learned from this entire project was that both the CDC designed ovitraps and the In2Care mosquito traps significantly reduced mosquito populations wherever they were deployed. However, neither was able to eliminate mosquitoes except in captive atriums and courtyards not subject to significant influxes of wind-blown mosquitoes from surrounding, untreated areas. To those clients with swimming pools in back yards surrounded by neighboring yards teeming with mosquitoes, the positive effect was minimal. Reducing the back yard mosquito population by 99% is not acceptable, if the 1% remaining still result in multiple mosquito bites every time family members take a swim or relax on the back patio with a refreshing soft drink or cocktail.

By comparison, though, using these devices in captive atriums and courtyards typically results in 100% control of mosquitoes.



Aedes Mosquitoes: 

  • Kingdom Animalia (ahn-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
  • Phylum Arthropoda (ahr-THROPP-uh-duh) — first described in 1829 by the French zoologist Pierre André Latreille [November 20, 1762 – February 6, 1833], using the two Greek roots αρθρον (AR-thrawn) = jointed + ποδ (pawd) = foot, in an obvious reference to animals with jointed feet, but in the more narrow context of the invertebrates, which have segmented bodies as well as jointed appendages;
  • Class Insecta (ehn-SEK-tuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Latin word insectum, a calque of the Greek word ἔντομον ( EN-toh-mawn) = “(that which is) cut into sections”; comprised of arthropods with chitinous external (exo-) skeletons, a three part body composed of a distinct head, thorax, and abdomen, the midmost part having three pairs of jointed legs, and the foremost part having a pair of compound eyes and antennae;
  • Subclass Pterygota (tare-ee-GOH-tah) — first described in 1888 by Lang, using the Greek roots πτερυξ (TARE-oos) = wing, to refer to insects with wings, or that had wings but in the process of evolution have since lost them;
  • Infraclass Neoptera (nee-OPP-tur-uh) — first described in 1890 by the Dutch entomologist Frederick Maurits van der Wulp (1818-1899) using the Greek roots νεος (NEE-ose) = youthful, new + πτερυ (TARE-ohn) = wing, to refer to winged insects that are capable of folding their wings over their abdomens, in contrast to more primitive winged insects that are unable to flex their wings in this manner (e.g., the dragonflies, in the infraclass Paleoptera);
  • Superorder Endopterygota (ehn-doh-tare-ee-GOH-tah) — first described by the English physician and entomologist David Sharp (1840-1922) using the Greek root ενδον (ENN-dohn) = within + the established expression pterygota (see above) to refer to insects within the latter subclass that undergo complete metamorphosis, i.e., larval, pupal, and adult stages
  • Order Diptera (DIPP-tur-ah) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Greek prefix δι- (dye) = two- + the Greek root πτερυ (TARE-ohn) = wing, to refer to insects having two flight wings on the mesothorax and reduced non-flight structures known as halteres — derived from the hind wings and used as flight stabilizers — on the metathorax, in contrast to typical winged insects that possess four flight wings, two on the mesothorax and two on the metathorax; flies in the order Strepsiptera also have but two flight wings and reduced non-flight halteres, but the halteres are on the mesothorax — derived from the forewings — and the flight wings are on the metathorax;
  • Suborder Nematocera (nee-matt-oh-SERR-uh) — a paraphyletic suborder, having one of its families, the Anisopodidae, a sister taxon to the suborder Brachysera; members of this suborder are elongated flies having thin, segmented antennae (plumose in some males) and mostly aquatic larvae; comprised of the mosquitoes (Culicidae), crane flies (Tipulidae), gnats (Mycetophilidae, Anisopodidae, and Sciaridae), black flies Simuliidae), and midges (Chironomidae, Cecidomyiidae, and Ceratopogonidae); the mostly aquatic larvae have distinct heads with mouthparts often modified for filter feeding; pupae are orthorrhaphous (i.e., adults emerge from the pupa through a straight seam in the pupal cuticle); bodies and legs of adults are usually elongate; many species form mating swarms of males, wherein competition for females is extreme;
  • Infraorder Culicomorpha (kew-lee-koh-MOR-fuh) — the mosquitoes (Superfamily Culicoidea) and black flies, buffalo gnats, and midges (Superfamily Chironomoidea);
  • Superfamily Culicoidea (kew-lee-KOY-dee-uh) — the menicus midges (Dixidae), frog-biting midges (Corethrellidae), phantom midges (Chjaoboridae), and mosquitoes (Cuilicidae)
  • Family Culicidae (kew-LISS-uh-dee) — the mosquitoes (from the Spanish word mosca = fly + the Spanish diminutive ito = small, thus little fly), small, midge-like flies whose females of most genera are ectoparasites with tube-like mouthparts (the proboscis) that pierce a hosts’ skin and enable the mosquito to draw in the host’s blood; the genus Toxorhynchites, whose members are called elephant mosquitoes and whose larvae are known as mosquito eaters, is one of many exceptions to the general rule that mosquitoes suck blood from their hosts, as its adults — which are among the largest known species of mosquitoes — are examples of the many kinds of mosquito whose adults of both sexes do not consume blood but subsist on carbohydrate-rich materials, such as honeydew, or saps and juices from damaged plants, refuse, fruit, and nectar instead, and their larvae prey on the larvae of other mosquitoes and similar nektonic prey in contrast with blood-sucking species of mosquitoes; the blood-sucking mosquitoes are members of two subfamilies, the Anophelinae and the Culicinae;
  • Subfamily Culicinae (kew-luh-SEE–nee) — the largest subfamily of Culicidae, comprised of 3,046 species of Culicinae mosquitoes in 108 genera and 11 tribes; they are small flies with fore wings for flight and hind wings reduced to halteres for balance, with long, slender, legs and proboscis-style mouth parts for feeding on vertebrate blood or plant fluids; females, which alone are blood feeders, require a high quality protein meal as a prerequisite to oviposition; bek g well adapted to host-finding, females move adroitly from one blood meal to another; on injecting saliva to prevent clotting of the host’s blood, pathogens picked up from other hosts are often injected as well, making the females efficient vectors of disease;
  • Tribe Aedini (EE-dinn-eye)— the largest tribe in the Culicinae, with 81 recognized genera;
  • Genus Aedes (EE-deez)— a genus of 12 species of mosquitoes, native to tropical and subtropical zones and now found on all continents except Antarctica; some species have been spread by human activity; Aedes albopictus, a particularly invasive species,recently spread to the New World, including the United States, via the used-tire trade.
  • Species Aedes aegypti (EE-deez ee-JIPP-tye) — First described by Linnaeus, Aedes aegypti (commonly known as the yellow fever mosquito) originated in Africa, was brought to the new world on ships, and has been a nuisance species in the United States for centuries. Ae. aegypti is the primary vector of yellow fever, a disease that is prevalent in tropical South America and Africa, and that often emerges in temperate regions during summer months; it is a container-inhabiting mosquito that often breeds in unused flowerpots, spare tires, untreated swimming pools, and drainage ditches. It thrives in urbanized areas, in close contact with people, and is exceptionally successful as a vector for a wide range of mosquito-borne diseases, including besides yellow fever, the Zika virus. Aedes aegypti males and female adults are day-active and feed on plant nectar; females bloodfeed on humans as a necessary prerequisite to the production of eggs. Eggs have the ability to survive desiccation for long periods of time, allowing eggs to be easily spread to new locations.
  • Species Aedes albopictus (EE-deez owl-boh-PIK-tiz) —

Zika virus: a Group IV positive-sense single stranded RNA virus, i.e., Group IV ((+)ssRNA), in an unassigned order, in the family Flaviviridae, and the genus Flavivirus.

  • Virus [from late Middle English (denoting snake venom): earlier, from the Latin word, virus, meaning literally a ‘slimy liquid or poison;’ the earliest medical sense of the term was that of a substance produced in the body as a result of disease, especially an infectious one capable of being transmitted to another person; that sense has been superseded by the current use of the term, due to an improved scientific understanding, now defines a virus as a small infectious agent that replicates only inside the living cells of other organisms; viruses are able to infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea (single celled microorganisms); scientific knowledge of viruses dates to 1892 when Dmitri Ivanovsky published an article that described a non-bacterial pathogen that infected tobacco plants, though Ivanovsky did not proceed further to identify the exact nature of the non-bacterial pathogen involved; six years later, Martinus Beijerinck published an identification of the tobacco mosaic virus; since that time some 5,000 virus species have been described in considerable detail; millions of types of viruses are, however, known to exist, to the point that viruses are found in nearly all of earth’s ecosystems on Earth, and are believed to comprise the most abundant type of biological entity in existence. While viruses are outside of an infected cell, and are not in the process of infecting a cell, they exist as virions, and consist of two or three parts. First is the genetic material, which is contained by all viruses and is made of either DNA or RNA; second is a protein coat, or capsid, surrounding and protecting the genetic material; and third, some — but not all — virions possess an envelope of lipids that surround the capsid. Virion shapes range in form from simple helixes and icosahedrals to more complex forms for others; most virions are one one-hundredth the size of the average bacterium, and thus are too small to be observed with an ordinary light microscope. How viruses evolved is subject to conjecture, but it seems most likely that a number of evolutionary processes have played a role, as it appears that some evolved from pieces of DNA — capable of moving between cells — known as plasmids, while others are believed to have evolved from bacteria. In evolution, viruses facilitate horizontal gene transfer, increasing genetic diversity. Some scientists consider viruses  to to constitute a legitimate life form, inasmuch as they contain genetic material, are capable of reproduction, and are subject to evolution through natural selection. Others point out that, because viruses lack cell structures and other key characters traditionally believed necessary to qualify as a legitimate life form, they are best considered as non-life forms existing on the very edge of life.]
  • RNA virus [RNA, or Ribonucleic acid, is a polymeric molecule implicated in various biological roles in coding, decoding, regulation, and expression of genes; both RNA and DNA are both nucleic acids, and, along with proteins and carbohydrates, constitute the three major macromolecules essential for all known forms of life; the nucleic acid in a RNA virus is usually single-stranded (ssRNA), but may be double-stranded (dsRNA); examples of human diseases caused by RNA viruses include Ebola hemorrhoragic fever, SARS, influenza, hepatitis C, West Nile fever, polio, and measles; the International Committee on Taxonomy of Viruses (ICTV) classifies RNA viruses as those that belong to Group III, Group IV or Group V of the Baltimore classification system of classifying viruses and does not consider viruses with DNA intermediates in their life cycle as RNA viruses; viruses with RNA as their genetic material that also include DNA intermediates in their replication cycle are termed retroviruses, and comprise Group VI of the Baltimore classification. Notable human retroviruses include HIV-1 and HIV-2; RNA viruses that explicitly exclude retroviruses are known as riboviruses;
  • Single stranded, positive-sense RNA viruses [RNA viruses can be further classified according to the sense or polarity of their RNA into negative-sense and positive-sense, or ambisense RNA viruses. Positive-sense viral RNA is similar to mRNA (a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression) and thus can be immediately translated by the host cell; negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation; as such, purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle; purified RNA of a negative-sense virus is not infectious by itself as it needs to be transcribed into positive-sense RNA; each virion can be transcribed to several positive-sense RNAs; ambisense RNA viruses resemble negative-sense RNA viruses; however, they also translate genes from the positive strand.]
  • Group IV single stranded, positive-sense RNA viruses [The genomes of Group IV, positive-sense single stranded RNA viruses are directly utilized as though it were mRNA; host ribosomes translate the virus genome into a single protein that is then modified by host and viral proteins, forming the various proteins that are needed for replication; one of these proteins includes RNA-dependent RNA polymerase (RNA replicase), which copies the viral RNA to form a double-stranded replicative form; it then directs the formation of new virions; within Group IV, three orders and 33 families are currently recognized, along with a long list of unclassified, i.e, unassigned families, species and genera.].
  • Order: Unassigned.
  • Family: Flaviviridae [from the Latin word flavus, meaning yellow, a reference to the Yellow Fever virus, so called because it typically causes jaundice in its victims; this family of viruses uses humans and other mammals as its natural hosts,and is primarily vectored through such arthropods as ticks and mosquitoes); it is comprised of several hundred species in four recognized genera, that are known as hepaciviruses that cause hepatitis, pestiviruses that produce hemorrhagic syndromes, abortion, and fatal mucosal disease, and finally the flavivirus that causes hemorrhagic fever, encephalitis, and the birth defect microcephaly.]
  • Genus: Flavivirus [a genus of well over 100 species that cause such diseases as West Nile, dengue, tick-borne encephalitis, yellow fever, and Zika; flaviviruses share a common size (40–65 nm), a common symmetry (enveloped, icosahedral nucleocapsid), a common nucleic acid (positive-sense, single-stranded RNA around 10,000–11,000 bases), and a common appearance when viewed via a scanning electron microscope; most flaviviruses are transmitted by infected arthropods (mosquitoes or ticks) and thus are classified as arboviruses; as a rule, most human infections with these viruses are incidental, with humans as a dead-end-host, as the human body is typically unable to replicate the virus in sufficiently high titers to reinfect the arthropod vectors needed to continue the virus lifecycle; exceptions to this rule include yellow fever, dengue, and Zika, which — while still requiring mosquito vectors — are so well adapted to humans that they do not require non-human animal hosts to reinfect their mosquito vectors, though the roles such non-human animal hosts play in facilitating transmission remain significant; other routes of arbovirus transmission include unsanitary handling of infected animal carcasses, blood transfusions, childbirth, and the consumption of unpasteurized milk products; flaviviruses are distinguished by the kind of vector (tick or mosquito) and by the virus group involved.]
  • Mosquito-borne grouping of flaviviruses;
  • Spondweni virus group of mosquito-borne flaviviruses;
  • Species: Flavivirus Zika [Named for the place where the virus was first isolated, in 1947 — the Zika Forest of Uganda — and spread by daytime-active mosquitoes in the genus Aedes, particularly A. aegypti and A. albopictus;  the infection it causes is known as Zika fever and often causes either no symptoms, or mild symptoms similar to a mild form of dengue fever. It has no cure and is treated by rest; since its discovery until recent times it has been known to occur only within a narrow equatorial belt from Africa to Asia, but managed to spread eastward across the Pacific Ocean, causing Zika virus outbreaks in 2013–2014 from Oceania to French Polynesia, New Caledonia, the Cook Islands, and Easter Island, and, later, in 2015, in Mexico, Central America, the Caribbean, and South America; there the Zika outbreak has now reached pandemic levels; as of 2016, the illness cannot be prevented by medications or vaccines, and often spreads from pregnant women to their babies, often resulting in microcephaly and other severe brain problems; Zika infections in adults often result in Guillain-Barré syndrome.]




Questions? Comments? Corrections? e-mail jerry.cates@entomobiotics.com. You may also leave a comment in the space provided below.

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