Global Center for Health Security

ArboNet (national srveillnace system for arboviral diseases. Also has information on mosquito borne disesaes)

RNA viruses remain in the cytoplasm except for retroviruses. RNA viruses can be classified based on their genome as follows:

Single-stranded + sense:

The RNA of positive strand RNA viruses is a mRNA (except retroviruses) and their genome is replicated by viral RNA dependent RNA polymerase (transcriptase) in the cytoplasm. The naked positive strand (coding, “sense”) RNA viral genome is sufficient to initiate infection by itself. The positive strand RNA virus genomes act as mRNA, bind to ribosomes and direct protein synthesis. After an RNA-dependent RNA polymerase is produced, a negative strand RNA template is synthesized. This template can then be used to generate more mRNA and to replicate the genome. Examples of + strand RNA viruses include the following:

Coronaviridae are large, enveloped, single-stranded RNA viruses. They are the largest known RNA viruses, with genomes ranging from 25 to 32 kb and virions of 118–140 nm in diameter. The family is divided into two subfamilies, the Coronavirinae and the Torovirinae. They can be distinguished on the basis of their nucleocapsids as the toroviruses have unique doughnut-shaped nucleocapsids. See Payne

–Coronavirus (SARS-CoV-2): 

Coronavirus disease 2019 (COVID-19), the highly contagious infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had a catastrophic effect on the world’s demographics resulting in more than 2.9 million deaths worldwide, emerging as the most consequential global health crisis since the era of the influenza pandemic of 1918.  Like other RNA viruses, SARS-CoV-2, while adapting to their new human hosts, is prone to genetic evolution with the development of mutations over time, resulting in variants that may have different characteristics than its ancestral strains. Several variants of SARS-CoV-2 have been described during the course of this pandemic, among which only a few are considered variants of concern (VOCs), given their impact on public health. The B.1.1.7 lineage (or VOC 202012) variant was the first VOC described in the United Kingdom (UK) in late December 2020, and subsequently, the B.1.351 lineage (or 501Y.V2) was reported in South Africa. A third VOC, B.1.1.248/B1.1.28/P1 (or 501Y.V3), was reported in Brazil in early January 2021, and more recently, the B.1.427/B.1.429 lineage was identified in California. Despite the unprecedented speed of vaccine development against the prevention of COVID-19 and robust global mass vaccination efforts, the emergence of these new SARS-CoV-2 variants threatens to overturn the significant progress made so far in limiting the transmission of this virus. See Napoli 

Enteroviruses:

Enterovirus is a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Enteroviruses are named by their transmission-route through the intestine. Serologic studies have distinguished 71 human enterovirus serotypes on the basis of antibody neutralization tests.

Since 1997, large outbreaks of severe hand, foot and mouth disease (HFMD) casued by diverse enterovirus A71 (EV-A71) subgengroups (such as B4, B5, C4 and C5) have been reported in the Asia Pacific region, resulting in millions of hospitalizations and substantial numbers of deaths. Increased EV-A71 detection and associated neurologic disease have also been documented worldwide, include the US in more recent years. Underlying factors might cause the emergency of EV-A71 subgenogroups within a specific locality; the accumulation of a sufficient number of suspetible young children and pathogen evolution might play critical roles. The changing epidemiology of respitatory pathogens as a consequence of COVID-19 has been documented. Although eV-A7 is mainly transmitted by the oral-fecal route, the effects of COVID-19 on eV-A71 transmission might be different from those of other respiratory viruses. However, the COVID-19 pandemic could have resulted in a large cohort of children who had greater susceptibility to EV-A71 infection. Inactivated EV-A71 vaccines have been developed in China and Taiwan but have only been used in China. Data has shown that those vaccines substantially reduced EV-A71 assocaited disease transmission in China. (Volume 30, Number 2, February 204, “Emering enterovirus A71 subgenogroup B5 causing severe hand, foot and mouth disease, Vietnam, 2023” CDC)

Coxsackieviruses are single-stranded RNA viruses. They belong to the Picornaviridae family and have a single-stranded, positive-sense RNA genome. Enterovirus infections in neonates can result in high morbidity and mortality. In 2023, a cluster of neonatal enterovirus cases associated with Coxsackie B4 and B5 occurred in San Diego, California. See CDC article

Poliovirus: Poliovirus is a member of the family of picornavirus. Picornaviruses are small, about 300 angstroms in diameter, and are comprised of an icosahedral protein coat and a single-stranded positive sense RNA genome.  Poliovirus infection occurs by the fecal-oral route. The host ingests the virus, which replicates in the alimentary tract. The virus is then shed in the feces. Most polio infections are asymptomatic. In about 5 percent of cases, the virus replicates in other tissues. Paralytic poliomyelitis occurs in less than 1 percent of cases. Poliovirus infection begins with the virus binds to the receptor CD155 on the host cell surface. CD155 is an immunoglobulin-like receptor also known as poliovirus receptor (PVR). The PVR polypeptide has an N-terminal sequence of three extracellular immunoglobulin-like domains, a transmembrane domain, and a cytoplasmic tail. The cellular function of PVR is unknown, but it is thought to play a role in cell adhesion and recognition.  See Medical Life Science

Paralysis is the most severe symptom associated with polio, because it can lead to permanent disability and death. Between 2 and 10 out of 100 people who have paralysis from poliovirus infection die, because the virus affects the muscles that help them breathe. See CDC.  Few diseases frightened parents more in the early part of the 20th century than polio did. Polio struck in the warm summer months, sweeping through towns in epidemics every few years. Though most people recovered quickly from polio, some suffered temporary or permanent paralysis and even death. Many polio survivors were disabled for life. They were a visible, painful reminder to society of the enormous toll this disease took on young lives. Polio is the common name for poliomyelitis,which comes from the Greek words for greyand marrow, referring to the spinal cord, and the suffix –itis, meaning inflammation. Poliomyelitis, shortened, became polio. For a time, polio was called infantile paralysis, though it did not affect only the young. See History of Vaccines. 

Poliomyelitis is caused by poliovirus, a typical picornavirus with a small non-lipid-containing virion approximately 27 nm in diameter. The icosahedral particle consists of sixty copies of each of the capsid proteins VP1, VP2, VP3 and VP4, encasing a single strand of messenger sense RNA. Polioviruses occur as serotypes 1, 2 and 3, and immunity to one type is believed not to protect against the other two. Humans are the only natural host, although primates and old world monkeys can be infected experimentally. See Cell.com

The single-stranded positive sense (+) RNA acts as messenger RNA (mRNA). The 5′ end of RNA has a long sequence that can fold into several stem-loops. The VPg protein and the stem-loops mimic the cap-binding complex, and these permit binding of the poliovirus mRNA to the host cell ribosome. The virus RNA codes for all the proteins of the virus into one large protein molecule called poly-protein.  This protein is cleaved into the individual proteins including the structural coat proteins and the RNA replicase that bring about replication of the poliovirus RNA. The assembly of intact poliovirus from coat protein molecules and RNA then follows. 

CDC recommends that children get polio vaccine to protect against polio, or poliomyelitis. Inactivated polio vaccine (IPV) is the only polio vaccine that has been given in the United States since 2000. IPV is given by shot in the leg or arm, depending on the patient’s age. Oral polio vaccine (OPV) is used in other countries. CDC recommends that children get four doses of polio vaccine. They should get one dose at each of the following ages: 2 months old, 4 months old, 6 through 18 months old, and 4 through 6 years old. Inactivated poliovirus vaccine (IPV), which is the only polio vaccine that has been given in the United States since 2000, protects almost all children (99 out of 100) who get all the recommended doses. For best protection, children should get four doses of polio vaccine. See CDC

Circulating vaccine-derived polioviruses (cVDPVs) can emerge and cause paralysis in areas with low population poliovirus immunity. Since 2017, large cVDPV type 2 (cVDPV2) outbreaks have occurred, primarily in Africa. Live, attenuated oral poliovirus vaccine (OPV) induces long-term protection against paralytic disease, and limits virus shedding in vaccinated persons with infection. Circulating vaccine-derived poliovirus (cVDPVs) outbreaks occur when OPV-related strains undergo prolonged circulation in communities with very low immunity against polioviruses, and the genetically reverted virus has regained neurovirulence (vaccine-derived poliovirus [VDPV] emergence). See CDC

Rubella virus (German Measles):

Measles, also known as rubeola or morbilli, is a contagious infection caused by measles virus (MeV), an RNA virus of the genus Morbillivirus within the family Paramyxoviridae. Rubella virus is the sole member of the genus Rubivirus in the family Togaviridae. Only one serotype has been identified. It contains three major structural polypeptides. Species of this genus also include the canine distemper virus in canines, rinderpest virus in cattle, and morbilliviruses which infect other animals. Humans are the natural hosts of MeV, and no animal reservoirs are known to exist.  

Measles is a spherical, 40- to 80-nm, positive-sense, single-stranded RNA virus with spike-like, hemagglutinin-containing surface projections. Postnatal rubella (German measles) is a generally mild, self-limited illness characterized by rash, lymphadenopathy, and low-grade fever. However, congenital rubella may cause a number of anomalies, depending on the organ system involved and gestational age. The disease is transmitted via direct or droplet contact with respiratory secretions. Rubella virus multiplies in cells of the respiratory system; this is followed by viremic spread to target organs. Congenital infection is transmitted transplacentally. Rubella occurs worldwide with a seasonal distribution. The peak incidence of infection is in late winter or early spring. There have been no major epidemics in the United States since vaccine licensure in 1969, and the incidence has decreased by 99 percent. Continued cases of congenital rubella are due to infection in unvaccinated, susceptible young women. See NCBI

MeV shares the gene order and transcription strategy that are fundamental characteristics of all other paramyxoviruses. Following cell entry, the genomic RNPs are released into the cytosol and the encapsidated viral RNA serves as a template of the RdRP complex for both transcription and replication. Transcription begins at the 3′ end of the genome and viral genes are transcribed in the 3′ to 5′direction with a sequential “stop–start” mechanism. MeV shares the gene order and transcription strategy that are fundamental characteristics of all other paramyxoviruses. Newly synthesized viral mRNAs are translated to viral proteins by using the host translation machinery. The negative-strand genome is also used to synthesize a positive-strand anti-genome, which is a complementary copy of the entire genome that produces more genomes via the same viral RNA polymerase. During replication, the newly synthesized genomic RNA is tightly wrapped with the N protein to provide a helical template for viral transcription and replication. See MDPI

Rubella can be prevented with MMR vaccine. This protects against three diseases: measles, mumps, and rubella. CDC recommends children get two doses of MMR vaccine, starting with the first dose at 12 through 15 months of age, and the second dose at 4 through 6 years of age. Teens and adults should also be up to date on their MMR vaccination. See CDC

Single-stranded (-) sense:

Ebola: is a single-stranded, negative RNA virus that belongs to the virus family Filoviridae. Marburg viruses are also included in the Filoviridae family. This virus family is characterized by their rod-shape, thread-like structure, varied length, and their membrane enclosed capsid. A capsid is a protein coat that encloses the viral genetic material. In Filoviridae viruses, the capsid is also enclosed in a lipid membrane that contains both host cell and viral components. This membrane assists the virus in infecting its host. Ebola viruses can be relatively large measuring up to 14,000 nm in length and 80 nm in diameter. They often take on a U shape. Ebola outbreaks have garnered serious attention as there was no known treatment, vaccine, or cure for the disease. In 2018 however, there was an outbreak of Ebola in the eastern Democratic Republic of the Congo. Scientists used four trial treatments to treat patients who had confirmed Ebola. Two of the treatments, one called, regeneron (REGN-EB3) and the other called, mAb114, were more successful than the other two treatments. Survival rates were much higher with these two methods. Both drugs are antiviral drugs and are currently being used on patients with confirmed Ebola. These drugs work by stopping the Ebola virus from being able to copy itself. Research continues to attempt to develop effective treatments and a cure for Ebola virus disease. See ThoughtCo

The Ebola virus (Zaire ebolavirus) vaccine is a replication-competent, live, attenuated recombinant vesicular stomatitis virus (rVSV) vaccine. It is known as rVSVΔG-ZEBOV-GP Ebola vaccine (brand name Ervebo®) and manufactured by Merck. The vaccine was approved by the U.S. Food and Drug Administration (FDA) on December 19, 2019, for the prevention of EVD caused by EBOV in people 18 years of age and older, based on the data from 12 clinical trials that included a total of 15,399 adults. See CDC

Hantaviruses

Hantaviruses are a large group of rodentborne single-stranded RNA viruses that cause clinical illness of varying severity in humans. Austria, and especially its southernmost federal states (Styria, Carinthia, and Burgenland) are endemic regions for the hantavirus puumala virus (PUUV) as well as for Dobrava/Belgrade virus (DOBV) in rare cases. Both hantavirus entities cause heorrhagic fecer with renal sndrome (HFRS); case-fatality rates of up to 1% in PUUV and up to 12% in DOBV. HFRS is characterized by strong inflammation affecitng vascular endothelia cells, leading to thrombocytopenia and potentially to disseminated intravascular coagulopathy. HFRS leads to renal failure of varying severity; half of patients develop respiratory symptoms. Hypoxia might lead to ICU admission for patients who need oxygen supply or organ support. (Krause, “Invasive Pulmonary Asperillosis in Critically Ill Patients with Hantavirus Infection, Austria” Emerging Infectious Diseases, 39)6), June 2024). 

Influenza virus: The World Health Organisation estimates that approximately one billion people are infected and up to 500 000 people die from influenza each year. The greatest burden of illness usually occurs among children, while the highest burden of severe disease (in terms of hospitalisation and death) occurs in those with underlying medical conditions, infants and young children, and elderly people. Influenza is usually self limiting in healthy individuals. Treatment of uncomplicated disease in healthy individuals is supportive and includes antipyretics, adequate fluid intake, rest, and staying off work or school until 24 hours after resolution of fever to limit spread to others. Individuals with complicated influenza may be helped by antiviral treatment. Treatment is most effective if started within 48 hours of symptom onset, and it should not be delayed while awaiting results of investigations.See MacPherson

Influenza antiviral drugs can be used to treat influenza infections, including human infections with influenza viruses that normally circulate in swine (swine influenza). There are four different antiviral drugs that are recommended for use in the United States for the treatment of influenza: oseltamivir, peramivir, zanamivir, and baloxavir. See CDC

Influenza is a viral infection that attacks one’s respiratory system; nose, throat and lungs. Influenza is commonly called the flu, but it’s not the same as stomach “flu” viruses that cause diarrhea and vomiting. At first, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a bother, you usually feel much worse with the flu. Influenza viruses travel through the air in droplets when someone with the infection coughs, sneezes or talks. You can inhale the droplets directly, or you can pick up the germs from an object — such as a telephone or computer keyboard — and then transfer them to your eyes, nose or mouth. See Mayo Clinic 

The influenza viruses are characterized by segmented, negative-strand RNA genomes requiring an RNA-dependent RNA polymerase of viral origin for replication. The particular structure of the influenza virus genome and function of its viral proteins enable antigenic drift and antigenic shift. These processes result in viruses able to evade the long-term adaptive immune responses in many hosts. The influenza A, B, and C viruses, representing three of the five genera of the family Orthomyxoviridae, are characterized by segmented, negative-strand RNA genomes. Sequencing has confirmed that these viruses share a common genetic ancestry; however, they have genetically diverged, such that reassortment – the exchange of viral RNA segments between viruses – has been reported to occur within each genus, or type, but not across types. Influenza A viruses are further characterized by the subtype of their surface glycoproteins, the hemagglutinin (HA) and the neuraminidase (NA). Influenza viruses have a standard nomenclature that includes virus type; species from which it was isolated (if non-human); location at which it was isolated; isolate number; isolate year; and, for influenza A viruses only, HA and NA subtype. Thus, A/Panama/2007/1999(H3N2) was isolate number 2007 of a human influenza A virus taken in the country of Panama in 1999, and it has an HA subtype 3 and an NA subtype 2. While many genetically distinct subtypes – 16 for HA and 9 for NA – have been found in circulating influenza A viruses, only three HA (H1, H2, and H3) and two NA (N1 and N2) subtypes have caused human epidemics, as defined by sustained, widespread, person-to-person transmission.  The influenza A and B virus genomes each comprise eight negative-sense, single-stranded viral RNA (vRNA) segments, while influenza C virus has a seven-segment genome. Influenza viruses recognize N-acetylneuraminic (sialic) acid on the host cell surface. Sialic acids are nine-carbon acidic monosaccharides commonly found at the termini of many glycoconjugates. Thus, they are ubiquitous on many cell types and in many animal species.

Inside the nucleus, the heterotrimeric viral RNA-dependent RNA polymerase carries out the transcription and replication of the vRNAs.  The replication of the influenza genome involves two steps: transcription of complimentary RNA (cRNA), followed by transcription of new vRNA copies using the cRNAs as templates. The cRNAs are produced by an unprimed process that relies on the correct complementation of free rNTPs (generally GTP and ATP) with the 3′ end of the vRNA template. Frontiers in Immunology 

Following attachment of the influenza virus HA protein (or the HEF protein of influenza C virus) to sialic acid, the virus is endocytosed. The acidity of the endosomal compartment is crucial to influenza virus uncoating in two ways. First, low pH triggers a conformational change in the HA, exposing a fusion peptide that mediates the merging of the viral envelope with the endosomal membrane, thus opening a pore through which the viral RNP’s are released into the host cell cytoplasm. Once liberated from the virion, RNPs are trafficked to the host cell nucleus by means of viral proteins’ nuclear localization signals (NLSs), which direct cellular proteins to import the RNPs and other viral proteins into the host cell nucleus. The nucleus is the location of all influenza virus RNA synthesis – both of the capped, polyadenylated messenger RNA (mRNA) that acts as the template for host-cell translation of viral proteins, and of the vRNA segments that form the genomes of progeny virus. The viral RNA-dependent RNA polymerase – a component of the RNPs imported into the nucleus – uses the negative-sense vRNA as a template to synthesize two positive-sense RNA species: mRNA templates for viral protein synthesis, and complementary RNA (cRNA) intermediates from which the RNA polymerase subsequently transcribes more copies of negative-sense, genomic vRNA. Unlike host cell mRNA, which is polyadenylated by a specific poly(A) polymerase, the poly(A) tail of influenza virus mRNA is encoded in negative-sense vRNA as a stretch of five to seven uracil residues, which the viral polymerase transcribes into the positive sense as a string of adenosines that form the poly(A) tail. See Palese

Marburg virus and the closely related Ravn virus: are the causative agents of Marburg virus disease, which has a case-fatality ratio of up to 88%. Marburg virus disease was initially detected in 1967 after simultaneous outbreaks in Marburg and Frankfurt in Germany, and in Belgrade, Serbia. Rousettus aegyptiacus fruit bats are considered natural hosts for Marburg virus, from which the virus is then transmitted to people. Marburg spreads between people via direct contact through broken skin or mucous membranes with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials such as bedding, clothing contaminated with these fluids. Healthcare workers have previously been infected while treating patients with suspected or confirmed MVD. Burial ceremonies that involve direct contact with the body of the deceased can also contribute to the transmission of Marburg. The incubation period varies from two to 21 days. Illness caused by Marburg virus begins abruptly, with high fever, severe headache, and severe malaise. Severe watery diarrhoea, abdominal pain and cramping, nausea, and vomiting can begin on the third day. Severe haemorrhagic manifestations may appear between five and seven days from symptom onset, and fatal cases usually have some form of bleeding, often from multiple areas. In fatal cases, death occurs most often between eight and nine days after symptom onset, usually preceded by severe blood loss and shock. In the early course of the disease, the clinical diagnosis of MVD is difficult to distinguish from many other tropical febrile illnesses due to the similarities in the clinical symptoms. Other viral haemorrhagic fevers need to be excluded, including Ebola virus disease, as well as malaria, typhoid fever, leptospirosis, rickettsial infections, and plague. Laboratory confirmation is primarily made by RT-PCR. Other tests can be used such as antibody-capture enzyme-linked immunosorbent assay (ELISA), antigen-capture detection tests, serum neutralization test, electron microscopy, and virus isolation by cell culture. Although no vaccines or antiviral treatments are approved to treat the virus, supportive care – rehydration with oral or intravenous fluids – and treatment of specific symptoms improve survival. A range of potential treatments are being evaluated, including blood products, immune therapies, and drug therapies. See Global Center for Health Security

Orthomyxoviruses:

Measles is caused by a virus in the paramyxovirus family, and is normally passed through direct contact and the air. The virus infects the respiratory tract, then spreads throughout the body, causing severe disease, complications and even death. Measles is caused by a single-stranded, negative sense, enveloped RNA virus with 1 serotype. It is classified as a member of the genus Morbillivirus in the Paramyxoviridae family. Humans are the only natural hosts of measles virus. See WHO. See CDC

–Mumps virus is a nonsegmented negative-strand RNA virus belonging to the family Paramyxoviridae.  Mumps virus was the main cause of aseptic meningitis before the introduction of live-attenuated mumps vaccine in the trivalent MMR vaccine.  In recent years, new outbreaks of mumps have occurred in college-age populations.  Mumps usually involves pain, tenderness, and swelling in one or both parotid salivary glands (cheek and jaw area). Swelling usually peaks in 1 to 3 days and then subsides during the next week. The swollen tissue pushes the angle of the ear up and out. As swelling worsens, the angle of the jawbone below the ear is no longer visible. Often, the jawbone cannot be felt because of swelling of the parotid. Mumps can occur in a person who is fully vaccinated, but vaccinated patients are less likely to present severe symptoms or complications than under- or unvaccinated cases. Mumps should be suspected in all patients with parotitis or mumps complications, regardless of age, vaccination status, and travel history. The mumps virus replicates in the upper respiratory tract and is transmitted person to person through direct contact with saliva or respiratory droplets of a person infected with mumps. The risk of spreading the virus increases the longer and the closer the contact a person has with someone who has mumps.  Mumps complications include orchitis, oophoritis, mastitis, meningitis, encephalitis, pancreatitis, and hearing loss. Complications can occur in the absence of parotitis and occur less frequently in vaccinated patients. Some complications of mumps are known to occur more frequently among adults than children. Vaccination is the best way to prevent mumps and mumps complications. This vaccine is included in the combination measles-mumps-rubella (MMR) and measles-mumps-rubella-varicella (MMRV) vaccines. Two doses of mumps vaccine are 88% (range 32% to 95%) effective at preventing the disease; one dose is 78% (range 49% to 91%) effective. See CDC

Rabies virus: is a rod- or bullet-shaped, single-stranded, negative-sense, unsegmented, enveloped RNA virus. The virus genome encodes five proteins.  The viral RNA uncoats in the cytoplasm of infected cells. The genome is transcribed by a virion-associated RNA-dependent RNA polymerase. Viral RNA is then translated into individual viral proteins. Replication occurs with synthesis of positive-stranded RNA templates for the production of progeny negative-stranded RNA. See Ruprochette

Rabies is transmitted only when the virus is introduced into open cuts or wounds in skin or mucous membranes. If there has been no exposure (as described in this section), postexposure treatment is not necessary. The likelihood of rabies infection varies with the nature and extent of exposure. Two categories of exposure (bite and nonbite) should be considered. Any penetration of the skin by teeth constitutes a bite exposure. Bites to the face and hands carry the highest risk, but the site of the bite should not influence the decision to begin treatment. Scratches, abrasions, open wounds, or mucous membranes contaminated with saliva or other potentially infectious material (such as brain tissue) from a rabid animal constitute nonbite exposures. If the material containing the virus is dry, the virus can be considered noninfectious. Immediate and thorough washing of all bite wounds and scratches with soap and water is an important measure for preventing rabies. In studies of animals, simple local wound cleansing has been shown to reduce markedly the likelihood of rabies See CDC 

Newcastle disease virus (NDV): blongs to the Paramyxoviridae family. NDV is a single stranded negative sense, enveloped RNA virus of avian origin that is highly attenuated in human and other primates because of strong host-range restriction. However, it is extemely infectious for domesticated pultry and other avian species cuasing high morbidity and mortality rates among infected birds. It thus have large ecnomic importance. Attenuated NDV has been evaluated as a vector for vaccines against SARS-Cov-2, Ebola, H5N1 influenze, West Nile and simian immunodificiency viruses. 

Double-stranded RNA:

Rotavirus: causes Gastroenteritis. Rotavirus is a double-stranded RNA virus, named for its classic “wheel-shaped” appearance on electron microscopy. Rotaviruses are found throughout the world, and most children are infected by 5 years of age. The frequency of infection is similar throughout the world; however, fatal infection is more likely in low-income regions throughout the globe. This is likely secondary to the lack of adequate healthcare facilities, increased rates of malnutrition, and lack of access to clean, sanitary hydration therapies. Rotaviruses replicate in mature enterocytes throughout the small intestinal lumen. This alteration in the epithelial cells of the small intestine leads to an osmotically active food bolus being moved into the large intestine, which subsequently leads to impaired water reabsorption in the large intestine. Impaired water reabsorption, in turn, causes the typical watery diarrhea seen in rotavirus infections. Another possible cause of rotavirus induced diarrhea includes increased intestinal motility, although the cause of this is unclear. Rotavirus has an incubation period varying from 1 to 3 days, after which symptoms appear abruptly with varying presentations. Symptoms congruent with infection are almost identical to other gastrointestinal infections; however, rotavirus infections tend to be more severe. Fever, diarrhea, and vomiting are the most common presenting symptoms. There is variability seen amongst infected patients ranging from short term, mild diarrhea to severe diarrhea with fever and vomiting. Treatment of rotavirus infection is directed at the relief of symptoms and the treatment and prevention of associated dehydration. Approximately 500,000 children under 5 years of age die annually secondary to diarrhea with rotavirus as the leading cause. It is estimated that 200,000 people die annually secondary to rotavirus infection. Severe dehydration is responsible for death in rotavirus infections.  See Budh 

Good hygiene like handwashing and cleanliness are important, but are not enough to control the spread of the disease. Rotavirus vaccine is the best way to protect your child against rotavirus disease. Most children (about 9 out of 10) who get the vaccine will be protected from severe rotavirus disease. About 7 out of 10 children will be protected from rotavirus disease of any severity. Two rotavirus vaccines are currently licensed for infants in the United States: RotaTeq® (RV5) is given in 3 doses at ages 2 months, 4 months, and 6 months. Rotarix® (RV1) is given in 2 doses at ages 2 months and 4 months. See FDA The first dose of either vaccine should be given before a child is 15 weeks of age. Children should receive all doses of rotavirus vaccine before they turn 8 months old. See CDC

RV particles possess their own transcription complexes (TCs), consisting of VP1, the viral RNA-dependent RNA polymerase (RdRp), and VP3, the viral capping enzyme (with phosphodiesterase, guanylyltransferase and methylase activities).  The RVA genome is approximately 18,500 bp in size and consists of 11 segments of dsRNA which encode 6 structural and 6 non-structural proteins. The genes are monocistronic, except for genome segment 11, which encodes two proteins. See Desselberger

Reoviruses

Single-stranded RNA + Reverse transcriptase:

Retroviruses convert their RNA to a hydrid RNA/DNA by virion reverse transcriptase (RT). RT then removes the RNA strand while synthesizing a new DNA strand to produce dsDNA which then integrates into the host nuclear DNA followed by production of mRNA by the host RNA polymerase.

HIV

nonenveloped or having an envelope surrounding a capsid which surrounds the genome.

segmented where the virion contains multiple RNA genomic fragments (influenza) or non-segmented where the virion contains a single genome (HIV)