Recent work has been done by virologists to learn more about the interference in infection of host cells and how DI genomes could potentially work as antiviral agents. The Dimmock & Easton, 2014 article explains that pre-clinical work is being done to test their effectiveness against influenza viruses. DI-RNAs have also been found to aid in the infection of fungi via viruses of the family "Partitiviridae" for the first time, which makes room for more interdisciplinary work.

Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell and introduces viral material into the cell. The major steps involved in viral entry are shown below. Despite the variation among viruses, there are several shared generalities concerning viral entry.

Despite decades of research, no vaccines currently exist.

Recombinant technology has however been used to target the formation of vaccines for HPIV-1, -2 and -3 and has taken the form of several live-attenuated intranasal vaccines. Two vaccines in particular were found to be immunogenic and well tolerated against HPIV-3 in phase I trials. HPIV-1 and -2 vaccine candidates remain less advanced.

Vaccine techniques which have been used against HPIVs are not limited to intranasal forms, but also viruses attenuated by cold passage, host range attenuation, chimeric construct vaccines and also introducing mutations with the help of reverse genetics to achieve attenuation.

Maternal antibodies may offer some degree of protection against HPIVs during the early stages of life via the colostrum in breast milk.

Parainfluenza viruses last only a few hours in the environment and are inactivated by soap and water. Furthermore, the virus can also be easily destroyed using common hygiene techniques and detergents, disinfectants and antiseptics.

Environmental factors which are important for HPIV survival are pH, humidity, temperature and the medium the virus in found within. The optimal pH is around the physiologic pH values (7.4 to 8.0), whilst at high temperatures (above 37 °C) and low humidity, infectivity reduces.

The majority of transmission has been linked to close contact, especially in nosocomial infections. Chronic care facilities and doctors' surgeries are also known to be transmission 'hotspots' with transmission occurring via aerosols, large droplets and also fomites (contaminated surfaces).

The exact infectious dose remains unknown.

Immunosuppressive therapy has been effective in halting the disease for laboratory animals.

, no approved vaccines are available. A phase-II vaccine trial used a live, attenuated virus, to develop viral resistance in 98% of those tested after 28 days and 85% still showed resistance after one year. However, 8% of people reported transient joint pain, and attenuation was found to be due to only two mutations in the E2 glycoprotein. Alternative vaccine strategies have been developed, and show efficacy in mouse models. In August 2014 researchers at the National Institute of Allergy and Infectious Diseases in the USA were testing an experimental vaccine which uses virus-like particles (VLPs) instead of attenuated virus. All the 25 people participated in this phase 1 trial developed strong immune responses. As of 2015, a phase 2 trial was planned, using 400 adults aged 18 to 60 and to take place at 6 locations in the Caribbean. Even with a vaccine, mosquito population control and bite prevention will be necessary to control chikungunya disease.

Lymphocytic choriomeningitis is not a commonly reported infection in humans, though most infections are mild and are often never diagnosed. Serological surveys suggest that approximately 1–5% of the population in the U.S. and Europe has antibodies to LCMV. The prevalence varies with the living conditions and exposure to mice, and it has been higher in the past due to lower standards of living. The island of Vir in Croatia is one of the biggest described endemic places of origin of LCMV in the world, with IFA testing having found LCMV antibodies in 36% of the population. Individuals with the highest risk of infection are laboratory personnel who handle rodents or infected cells. Temperature and time of year is also a critical factor that contributes to the number of LCMV infections, particularly during fall and winter when mice tend to move indoors. Approximately 10–20% of the cases in immunocompetent individuals are thought to progress to neurological disease, mainly as aseptic meningitis. The overall case fatality rate is less than 1% and people with complications, including meningitis, almost always recover completely. Rare cases of meningoencephalitis have also been reported. More severe disease is likely to occur in people who are immunosuppressed.

More than 50 infants with congenital LCMV infection have been reported worldwide. The probability that a woman will become infected after being exposed to rodents, the frequency with which LCMV crosses the placenta, and the likelihood of clinical signs among these infants are still poorly understood. In one study, antibodies to LCMV were detected in 0.8% of normal infants, 2.7% of infants with neurological signs and 30% of infants with hydrocephalus. In Argentina, no congenital LCMV infections were reported among 288 healthy mothers and their infants. However, one study found that two of 95 children in a home for people with severe mental disabilities had been infected with this virus. The prognosis for severely affected infants appears to be poor. In one series, 35% of infants diagnosed with congenital infections had died by the age of 21 months.

Transplant-acquired lymphocytic choriomeningitis proves to have a very high morbidity and mortality rate. In the three clusters reported in the U.S. from 2005 to 2010, nine of the ten infected recipients died. One donor had been infected from a recently acquired pet hamster while the sources of the virus in the other cases were unknown.

Prophylactic vaccination is available against poliomyelitis, measles, Japanese encephalitis, and rabies. Hyper immune immunoglobulin has been used for prophylaxis of measles, herpes zoster virus, HSV-2, vaccine, rabies, and some other infections in high-risk groups.

Development of new therapies has been hindered by the lack of appropriate animal model systems for some important viruses and also because of the difficulty in conducting human clinical trials for diseases that are rare. Nonetheless, numerous innovative approaches to antiviral therapy are available including candidate thiazolide and purazinecarboxamide derivatives with potential broad-spectrum antiviral efficacy. New herpes virus drugs include viral helicase-primase and terminase inhibitors. A promising new area of research involves therapies based on enhanced understanding of host antiviral immune responses.

Vaccines are available (ATCvet codes: for the inactivated vaccine, for the live vaccine, plus various combinations).

Given that avian reovirus infections are widespread, the viruses are relatively resistant outside the host, and that vertical and horizontal transmission occurs, eradicating avian reovirus infection in commercial chicken flocks is very unlikely. In addition, absence of detectable seroconversion and failure to detect virus in cloacal swabs are unreliable indicators of resisting infection, or transmission via the egg. Thus, the most proactive and successful approach to controlling this disease is through vaccination. Since chicks are more prone to being detrimentally affected by the disease right after hatching, vaccine protocols that use live and killed vaccines are designed to provide protection during the very early stages of life. This approach has been accomplished through active immunity after early vaccination and a live vaccine or passive immunity from maternal antibodies followed with vaccination of the breeder hens. Currently, efforts toward administering inactivated or live vaccines to breeding stock to allow passive immunity to the offspring via the yolk are being taken.

Avian reoviruses belong to the genus "Orthoreovirus", and "Reoviridae" family. They are non-enveloped viruses that undergo replication in the cytoplasm of infected cells. It has icosahedral symmetry and contains a double-shelled arrangement of surface protein. Virus particles can range between 70–80 nm. Morphologically, the virus is a double stranded RNA virus that is composed of ten segments. The genome and proteins that are encoded by the genome can be separated into three different sizes ranging from small, medium, or large. Of the eleven proteins that are encoded for by the genome, two are nonstructural, while the remaining nine are structural.

Avian reoviruses can withstand a pH range of 3.0–9.0. Ambient temperatures are suitable for the survival of these viruses, which become inactive at 56 °C in less than an hour. Common areas where this virus can survive include galvanized metal, glass, rubber, feathers, and wood shavings. Avian reovirus can survive for up to ten days on these common areas in addition to up to ten weeks in water.

Cultivation and observation of the effects of avian reovirus is most often performed in chicken embryos. If infected into the yolk sac, the embryo will succumb to death accompanied by hemorrhaging of the embryos and cause the foci on the liver to appear yellowish-green. There are several primary chicken cell cultures/areas that are susceptible to avian reoviruses, which include the lungs, liver, kidney, and fibroblasts of the chick embryo. Of the following susceptible areas, liver cells from the chick embryo have been found to be the most sensitive for primary isolation from clinical material.

Typically, the CPE effect of avian reoviruses is the production of syncytia. CPE, or cytopathic effects are the visible changes in a host cell that takes place because of viral infection. Syncytia is a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.

Currently, no specific treatment for chikungunya is available. Supportive care is recommended, and symptomatic treatment of fever and joint swelling includes the use of nonsteroidal anti-inflammatory drugs such as naproxen, non-aspirin analgesics such as paracetamol (acetaminophen) and fluids. Aspirin is not recommended due to the increased risk of bleeding. Despite anti-inflammatory effects, corticosteroids are not recommended during the acute phase of disease, as they may cause immunosuppression and worsen infection.

Passive immunotherapy has potential benefit in treatment of chikungunya. Studies in animals using passive immunotherapy have been effective, and clinical studies using passive immunotherapy in those particularly vulnerable to severe infection are currently in progress. Passive immunotherapy involves administration of anti-CHIKV hyperimmune human intravenous antibodies (immunoglobulins) to those exposed to a high risk of chikungunya infection. No antiviral treatment for chikungunya virus is currently available, though testing has shown several medications to be effective "in vitro".

In virology, defective interfering particles (DIPs), also known as defective interfering viruses, are spontaneously generated virus mutants in which a critical portion of the particle's genome has been lost due to defective replication. DIPs are derived from and associated with their parent virus, and particles are classed as DIPs if they are rendered non-infectious due to at least one essential gene of the virus being lost or severely damaged as a result of the defection. A DIP can usually still penetrate host cells, but requires another fully functional virus particle (the 'helper' virus) to co-infect a cell with it, in order to provide the lost factors. The existence of DIPs has been known about for decades, and they can occur within nearly every class of both DNA and RNA viruses.

Infection with Japanese encephalitis confers lifelong immunity. There are currently three vaccines available: SA14-14-2, IC51 (marketed in Australia and New Zealand as JESPECT and elsewhere as IXIARO) and ChimeriVax-JE (marketed as IMOJEV). All current vaccines are based on the genotype III virus.

A formalin-inactivated mouse-brain derived vaccine was first produced in Japan in the 1930s and was validated for use in Taiwan in the 1960s and in Thailand in the 1980s. The widespread use of vaccine and urbanization has led to control of the disease in Japan, Korea, Taiwan, and Singapore. The high cost of this vaccine, which is grown in live mice, means that poorer countries have not been able to afford to give it as part of a routine immunization program.

The most common adverse effects are redness and pain at the injection site. Uncommonly, an urticarial reaction can develop about four days after injection. Vaccines produced from mouse brain have a risk of autoimmune neurological complications of around 1 per million vaccinations. However where the vaccine is not produced in mouse brains but in vitro using cell culture there is little adverse effects compared to placebo, the main side effects are headache and myalgia.

The neutralizing antibody persists in the circulation for at least two to three years, and perhaps longer. The total duration of protection is unknown, but because there is no firm evidence for protection beyond three years, boosters are recommended every three years for people who remain at risk. Furthermore, there is also no data available regarding the interchangeability of other JE vaccines and IXIARO.

In September 2012 the Indian firm Biological E. Limited has launched an inactivated cell culture derived vaccine based on SA 14-14-2 strain which was developed in a technology transfer agreement with Intercell and is a thiomersal-free vaccine.

The theory that cancer could be caused by a virus began with the experiments of Oluf Bang and Vilhelm Ellerman in 1908 who first show that avian erythroblastosis (a form of chicken leukemia) could be transmitted by cell-free extracts. This was subsequently confirmed for solid tumors in chickens in 1910-1911 by Peyton Rous.

By the early 1950s it was known that viruses could remove and incorporate genes and genetic material in cells. It was suggested that these new genes inserted into cells could make the cell cancerous. Many of these viral oncogenes have been discovered and identified to cause cancer.

The main viruses associated with human cancers are human papillomavirus, hepatitis B and hepatitis C virus, Epstein-Barr virus, human T-lymphotropic virus, Kaposi's sarcoma-associated herpesvirus (KSHV) and Merkel cell polyomavirus. Experimental and epidemiological data imply a causative role for viruses and they appear to be the second most important risk factor for cancer development in humans, exceeded only by tobacco usage. The mode of virally induced tumors can be divided into two, "acutely transforming" or "slowly transforming". In acutely transforming viruses, the viral particles carry a gene that encodes for an overactive oncogene called viral-oncogene (v-onc), and the infected cell is transformed as soon as v-onc is expressed. In contrast, in slowly transforming viruses, the virus genome is inserted, especially as viral genome insertion is an obligatory part of retroviruses, near a proto-oncogene in the host genome. The viral promoter or other transcription regulation elements in turn cause overexpression of that proto-oncogene, which in turn induces uncontrolled cellular proliferation. Because viral genome insertion is not specific to proto-oncogenes and the chance of insertion near that proto-oncogene is low, slowly transforming viruses have very long tumor latency compared to acutely transforming viruses, which already carry the viral oncogene.

Hepatitis viruses, including hepatitis B and hepatitis C, can induce a chronic viral infection that leads to liver cancer in 0.47% of hepatitis B patients per year (especially in Asia, less so in North America), and in 1.4% of hepatitis C carriers per year. Liver cirrhosis, whether from chronic viral hepatitis infection or alcoholism, is associated with the development of liver cancer, and the combination of cirrhosis and viral hepatitis presents the highest risk of liver cancer development. Worldwide, liver cancer is one of the most common, and most deadly, cancers due to a huge burden of viral hepatitis transmission and disease.

Through advances in cancer research, vaccines designed to prevent cancer have been created. The hepatitis B vaccine is the first vaccine that has been established to prevent cancer (hepatocellular carcinoma) by preventing infection with the causative virus. In 2006, the U.S. Food and Drug Administration approved a human papilloma virus vaccine, called Gardasil. The vaccine protects against four HPV types, which together cause 70% of cervical cancers and 90% of genital warts. In March 2007, the US Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) officially recommended that females aged 11–12 receive the vaccine, and indicated that females as young as age 9 and as old as age 26 are also candidates for immunization.

Marburgviruses are World Health Organization Risk Group 4 Pathogens, requiring Biosafety Level 4-equivalent containment, laboratory researchers have to be properly trained in BSL-4 practices and wear proper personal protective equipment.

There are currently no Food and Drug Administration-approved vaccines for the prevention of MVD. Many candidate vaccines have been developed and tested in various animal models. Of those, the most promising ones are DNA vaccines or based on Venezuelan equine encephalitis virus replicons, vesicular stomatitis Indiana virus (VSIV) or filovirus-like particles (VLPs) as all of these candidates could protect nonhuman primates from marburgvirus-induced disease. DNA vaccines have entered clinical trials. Marburgviruses are highly infectious, but not very contagious. Importantly, and contrary to popular belief, marburgviruses do not get transmitted by aerosol during natural MVD outbreaks. Due to the absence of an approved vaccine, prevention of MVD therefore relies predominantly on behavior modification, proper personal protective equipment, and sterilization/disinfection.

Lesions of paravaccinia virus will clear up with little to no scaring after 4 to 8 weeks. An antibiotic may be prescribed by a physician to help prevent bacterial infection of the lesion area. In rare cases, surgical removal of the lesions can be done to help increase rate of healing, and help minimize risk of bacterial or fungal infection. Upon healing, no long term side effects have been reported.

The virus is most often spread by person to person contact with the stool or saliva of the infected person. Two types of vaccines have been developed to prevent the occurrence and spread of the poliomyelitis virus. The first is an inactivated, or killed, form of the virus and the second is an attenuated, or weakened, form of the virus. The development of vaccines has successfully eliminated the disease from the United States. There are continued vaccination efforts in the U.S. to maintain this success rate as this disease still occurs in some areas of the world.

Paravaccinia virus originates from livestock infected with bovine papular stomatitis. When a human makes physical contact with the livestock's muzzle, udders, or an infected area, the area of contact will become infected. Livestock may not show symptoms of bovine papular stomatitis and still be infected and contagious. Paravaccinia can enter the body though all pathways including: skin contact by mechanical means, through the respiratory tract, or orally. Oral or respiratory contraction may be more likely to cause systemic symptoms such as lesions across the whole body

A person who has not previously been infected with paravaccinia virus should avoid contact with infected livestock to prevent contraction of disease. There is no commercially available vaccination for cattle or humans against paravaccinia. However, following infection, immunization has been noted in humans, making re-infection difficult. Unlike other pox viruses, there is no record of contracting paravaccinia virus from another human. Further, cattle only show a short immunization after initial infection, providing opportunity to continue to infect more livestock and new human hosts.

One study has focused on identifying OROV through the use of RNA extraction from reverse transcription-polymerase chain reaction. This study revealed that OROV caused central nervous system infections in three patients. The three patients all had meningoencephalitis and also showed signs of clear lympho-monocytic cellular pattern in CSF, high protein, and normal to slightly decreased glucose levels indicating they had viral infections. Two of the patients already had underlying infections that can effect the CNS and immune system and in particular one of these patients has HIV/AIDS and the third patient has neurocysticercosis. Two patients were infected with OROV developed meningitis and it was theorized that this is due to them being immunocompromised. Through this it was revealed that it's possible that the invasion of the central nervous system by the oropouche virus can be performed by a pervious blood-brain barrier damage.

Estimated percent of new cancers attributable to the virus worldwide in 2002. NA indicates not available.

The association of other viruses with human cancer is continually under research.

Oropouche Fever has no cure or specific therapy so treatment is done by relieving the pain of the symptoms through symptomatic treatment. Certain oral analgesic and anti-inflammatory agents can help treat headaches and body pains. In extreme cases of oropouche fever the drug, Ribavirin is recommended to help against the virus. This is called antiviral therapy. Treatments also consist of drinking lots of fluids to prevent dehydration.

Asprin is not a recommended choice of drug because it can reduce blood clotting and may aggravate the hemorrhagic effects and prolong recovery time.

The infection is usually self-limiting and complications are rare. This illness usually lasts for about a week but in extreme cases can be prolonged. Patients usually recover fully with no long term ill effects. There have been no recorded fatalities resulting from oropouche fever.

There is no cure for polioencephalitis so prevention is essential. Many people that become infected will not develop symptoms and their prognosis is excellent. However, the prognosis is dependent on the amount of cellular damage done by the virus and the area of the brain affected. Many people that develop more severe symptoms can have lifelong disabilities or it can lead to death. Supportive treatments include bed rest, pain relievers, and a nutritious diet. Many drugs have been used to treat psychiatric symptoms such as Clonazepam for insomnia and Desvenlafaxine or Citalopram for depressed mood.

There is no specific treatment for Japanese encephalitis and treatment is supportive, with assistance given for feeding, breathing or seizure control as required. Raised intracranial pressure may be managed with mannitol. There is no transmission from person to person and therefore patients do not need to be isolated.

A breakthrough in the field of Japanese encephalitis therapeutics is the identification of macrophage receptor involvement in the disease severity. A recent report of an Indian group demonstrates the involvement of monocyte and macrophage receptor CLEC5A in severe inflammatory response in Japanese Encephalitis infection of the brain. This transcriptomic study provides a hypothesis of neuroinflammation and a new lead in development of appropriate therapeutic against Japanese encephalitis.