The disease can be prevented in horses with the use of vaccinations. These vaccinations are usually given together with vaccinations for other diseases, most commonly WEE, VEE, and tetanus. Most vaccinations for EEE consist of the killed virus. For humans there is no vaccine for EEE so prevention involves reducing the risk of exposure. Using repellent, wearing protective clothing, and reducing the amount of standing water is the best means for prevention

Risk factors independently associated with developing a clinical infection with WNV include a suppressed immune system and a patient history of organ transplantation. For neuroinvasive disease the additional risk factors include older age (>50+), male sex, hypertension, and diabetes mellitus.

A genetic factor also appears to increase susceptibility to West Nile disease. A mutation of the gene "CCR5" gives some protection against HIV but leads to more serious complications of WNV infection. Carriers of two mutated copies of "CCR5" made up 4.0 to 4.5% of a sample of West Nile disease sufferers, while the incidence of the gene in the general population is only 1.0%.

The virus’s transmission cycle in the wild is similar to the continuous sylvatic cycle of yellow fever and is believed to involve wild primates (monkeys) as the reservoir and the tree-canopy-dwelling "Haemagogus" species mosquito as the vector. Human infections are strongly associated with exposure to humid tropical forest environments. Chikungunya virus is closely related, producing a nearly indistinguishable, highly debilitating arthralgic disease. On February 19, 2011, a Portuguese-language news source reported on a recent survey which revealed Mayaro virus activity in Manaus, Amazonas State, Brazil. The survey studied blood samples from 600 residents of Manaus who had experienced a high fever; Mayaro virus was identified in 33 cases. Four of the cases experienced mild hemorrhagic (bleeding) symptoms, which had not previously been described in Mayaro virus disease. The report stated that this outbreak is the first detected in a metropolitan setting, and expressed concern that the disease might be adapting to urban species of mosquito vectors, which would make it a risk for spreading within the country. A study published in 1991 demonstrated that a colonized strain of Brazilian "Aedes albopictus" was capable of acquiring MAYV from infected hamsters and subsequently transmitting it and a study published in October 2011 demonstrated that "Aedes aegypti" can transmit MAYV, supporting the possibility of wider transmission of Mayaro virus disease in urban settings.

The mortality rate of chikungunya is slightly less than 1 in 1000. Those over the age of 65, neonates, and those with underlying chronic medical problems are most likely to have severe complications. Neonates are vulnerable as it is possible to vertically transmit chikungunya from mother to infant during delivery, which results in high rates of morbidity, as infants lack fully developed immune systems. The likelihood of prolonged symptoms or chronic joint pain is increased with increased age and prior rheumatological disease.

Contact with farm animals can lead to disease in farmers or others that come into contact with infected animals. Glanders primarily affects those who work closely with horses and donkeys. Close contact with cattle can lead to cutaneous anthrax infection, whereas inhalation anthrax infection is more common for workers in slaughterhouses, tanneries and wool mills. Close contact with sheep who have recently given birth can lead to clamydiosis, or enzootic abortion, in pregnant women, as well as an increased risk of Q fever, toxoplasmosis, and listeriosis in pregnant or the otherwise immunocompromised. Echinococcosis is caused by a tapeworm which can be spread from infected sheep by food or water contaminated with feces or wool. Bird flu is common in chickens. While rare in humans, the main public health worry is that a strain of bird flu will recombine with a human flu virus and cause a pandemic like the 1918 Spanish flu. In 2017, free range chickens in the UK were temporarily ordered to remain inside due to the threat of bird flu. Cattle are an important reservoir of cryptosporidiosis and mainly affects the immunocompromised.

Vertical transmission, the transmission of a viral or bacterial disease from the female of the species to her offspring, has been observed in various West Nile virus studies, amongst different species of mosquitoes in both the laboratory and in nature. Mosquito progeny infected vertically in autumn, may potentially serve as a mechanism for WNV to overwinter and initiate enzootic horizontal transmission the following spring, although it likely plays little role in transmission in the summer and fall.

Outbreaks of zoonoses have been traced to human interaction with and exposure to animals at fairs, petting zoos, and other settings. In 2005, the Centers for Disease Control and Prevention (CDC) issued an updated list of recommendations for preventing zoonosis transmission in public settings. The recommendations, developed in conjunction with the National Association of State Public Health Veterinarians, include educational responsibilities of venue operators, limiting public and animal contact, and animal care and management.

The study of RRF has been recently facilitated by the development of a mouse model. Mice infected with RRV develop hind-limb arthritis/arthralgia which is similar to human disease. The disease in mice is characterized by an inflammatory infiltrate including macrophages which are immunopathogenic and exacerbate disease. Furthermore, mice deficient in the C3 protein do not suffer from severe disease following infection. This indicates that an aberrant innate immune response is responsible for severe disease following RRV infection.

Prevention strategies include reducing the breeding of midges through source reduction (removal and modification of breeding sites) and reducing contact between midges and people. This can be accomplished by reducing the number of natural and artificial water-filled habitats and encourage the midge larvae to grow.

Oropouche fever is present in epidemics so the chances of one contracting it after being exposed to areas of midgets or mosquitoes is rare.

, 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.

There is no cure for EEE. Treatment consists of corticosteroids, anticonvulsants, and supportive measures (treating symptoms) such as intravenous fluids, tracheal intubation, and antipyretics. About four percent of humans known to be infected develop symptoms, with a total of about six cases per year in the US. A third of these cases die, and many survivors suffer permanent brain damage.

The majority of MVEV infections are sub-clinical, i.e. do not produce disease symptoms, although some people may experience a mild form of the disease with symptoms such as fever, headaches, nausea and vomiting and only a very small number of these cases go on to develop MVE. In fact, serological surveys which measure the level of anti-MVEV antibodies within the population estimate that only 1 in 800-1000 of all infections result in clinical disease.

The incubation period following exposure to the virus is around 1 to 4 weeks. Following infection, a person will have lifelong immunity to the virus. When a patient appears to show MVE symptoms and has been in an MVE-endemic area during the wet season, when outbreaks usually occur, MVE infection must be confirmed by laboratory diagnosis, usually by detection of a significant rise of MVE-specific antibodies in the patient's serum.

Of those who contract MVE, one-quarter die from the disease.

Mayaro virus disease is a mosquitoborne zoonotic pathogen endemic to certain humid forests of tropical South America. Infection with Mayaro virus causes an acute, self-limited dengue-like illness of 3–5 days' duration. The causative virus, abbreviated MAYV, is in the family Togaviridae, and genus Alphavirus. It is closely related to other alphaviruses that produce a dengue-like illness accompanied by long-lasting arthralgia. It is only known to circulate in tropical South America.

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.

Prophylaxis by vaccination, as well as preventive measures like protective clothing, tick control, and mosquito control are advised. The vaccine for KFDV consists of formalin-inactivated KFDV. The vaccine has a 62.4% effectiveness rate for individuals who receive two doses. For individuals who receive an additional dose, the effectiveness increases to 82.9%. Specific treatments are not available.

There is currently no vaccine available. The primary method of disease prevention is minimizing mosquito bites, as the disease is only transmitted by mosquitoes. Typical advice includes use of mosquito repellent and mosquito screens, wearing light coloured clothing, and minimising standing water around homes (e.g. removing Bromeliads, plant pots, garden ponds). Staying indoors during dusk/dawn hours when mosquitos are most active may also be effective. Bush camping is a common precipitant of infection so particular care is required.

There are a variety of animals thought to be reservoir hosts for the disease, including porcupines, rats, squirrels, mice and shrews. The vector for disease transmission is "Haemaphysalis spinigera", a forest tick. Humans contract infection from the bite of nymphs of the tick.

MVEV is a mosquito-borne virus that is maintained in a bird-mosquito-bird cycle. Water birds from the order Ciconiiformes, including herons and cormorants, provide the natural reservoir for MVEV. The major mosquito vector is "Culex annulirostris". Human infection occurs only through bites from infected mosquitoes; the virus cannot be transmitted from person to person.

Rocio viral encephalitis is an epidemic flaviviral disease of humans first observed in São Paulo State, Brazil, in 1975. Low-level enzootic transmission is likely continuing in the epidemic zone, and with increased deforestation and population expansion, additional epidemics caused by Rocio virus are highly probable. If migratory species of birds are, or become involved in, the virus transmission cycle, the competency of a wide variety of mosquito species for transmitting Rocio virus experimentally suggest that the virus may become more widely distributed. The encephalitis outbreak in the western hemisphere caused by West Nile virus, a related flavivirus, highlights the potential for arboviruses to cause severe problems far from their source enzootic foci.

The causative Rocio virus belongs to the genus "Flavivirus" (the same genus as the Zika virus) in family Flaviviridae and is closely related serologically to Ilhéus, St. Louis encephalitis, Japanese encephalitis and Murray Valley encephalitis viruses.

West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family Flaviviridae, specifically from the genus Flavivirus which also contain the Zika virus, dengue virus, and the yellow fever virus. The West Nile virus is primarily transmitted through mosquitoes, mostly by the Culex species. However, ticks have been found to carry the virus. The primary hosts of WNV are birds, so that the virus remains within a "bird-mosquito-bird" transmission cycle.

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.

During 1975 and 1976, Rocio virus was responsible for several epidemics of meningoencephalitis in coastal communities in southern São Paulo, Brazil. The outbreaks affected over 1,000 people and killed about 10% of those infected, but apparently responded well to treatment for viral encephalitides. The disease progresses rapidly after onset, with patients dying within 5 days of symptoms first appearing. The disease first presents with fever, headache, vomiting, and conjunctivitis, then progresses to neurological symptoms (confusion, disorientation, etc.) and muscle weakness; about one-third of cases enter a coma, and a third of those patients die, although supportive care such as intensive nursing and symptomatic treatment might reduce the case fatality rate to 4%. Survivors show neurological and psychological after-effects (sequelae) in about 20% of cases.

Mosquitoes, primarily from the genus "Culex", become infected by feeding on birds infected with the Saint Louis encephalitis virus. Infected mosquitoes then transmit the Saint Louis encephalitis virus to humans and animals during the feeding process. The Saint Louis encephalitis virus grows both in the infected mosquito and the infected bird, but does not make either one sick. Only infected mosquitoes can transmit Saint Louis encephalitis virus. Once a human has been infected with the virus it is not transmissible from that individual to other humans.

It is transmitted by the bite of several species of infected ticks, including "Ixodes scapularis", "I. ricinus" and "I. persulcatus", or (rarely) through the non-pasteurized milk of infected cows.

There are no vaccines or any other treatments specifically for Saint Louis encephalitis virus, although one study showed that early use of interferon-alpha2b may decrease the severity of complications.