**9. Conclusion and perspective**

biological material from the host cell to form an infectious vesicle.These particles may fuse with other biologically functional identities, potentially leading to the initiation of new in‐ fections, which can result in the formation of completed and perfect virions. Interference with the processes and network signaling involving classical virion formation has been a common target for drug development. However, in reality, the perfect virion *in vivo* has not been visualized, suggesting an alternate form of virion may exist *in vivo*. Consequently, the real structures needed to design the intervention remains elusive. Furthermore, diseases in‐ duced by arboviruses are acute illnesses where timing is critical. Infected individuals nor‐ mally delay in seeking professional help, resulting in the subjects arriving at the hospital in a far worsen condition. Thus, the availability of intervention drugs, the timing of the admin‐

istration and the effect of the drugs on the arboviral infections remain critical issues.

**8. Vaccine prevention for arboviral infections**

has been used in Russia, Germany, Austria, and China [93].

Prognosis depends on the particular type of arbovirus causing disease, and on the age and prior health status of the patient. The prognosis is worse in very young patients, elderly pa‐ tients, and patients with compromised immune systems. LAC encephalitis most often oc‐ curs in children, while WNV and SLV encephalitis usually occur in persons older than 50 years of age [20]. Encephalitis caused by EEV and JEV carries a high risk for serious neuro‐ logical damage and death. Death rates range all the way up to 20% for arboviral encephali‐ tis, and the rates of lifelong effects due to brain damage can reach 60% for some types of

Infection with an arbovirus provides immunity to that specific virus, but not to other arbovi‐ ruses, suggesting that arboviral infection is a vaccine preventable disease. Thus, the devel‐ opment of new, more effective vaccines and the appropriate animal models in which to test them are paramount. Although for many important arboviruses, there are currently no ap‐ proved vaccines available for human use, while for some, safe and effective vaccines have been used for decades. For instance, a clinical approved inactivated vaccine against TBEV

JEV is one of the few arboviruses for which a vaccine is available. The JEV vaccine made from infected mouse brain can achieve efficacies of at least 80% [94]. But because of the cost and safety concerns, development of a better JEV vaccine has been an ongoing project. For example, the development of a live-attenuated virus vaccine (SA14-14-2, for use in China and a part of Asia) and more recently, in March 2009, the FDA approved a new, inactivated cell-culture-derived JEV vaccine (IXIARO) for use in adult travelers over the age of 17 [95-98]. In addition, a live-attenuated yellow fever–Japanese encephalitis chimeric vaccine

(IMOJEV™) was recently licensed in Australia and is under review in Thailand [98].

**7. Prognosis**

84 Encephalitis

arboviruses.

Arboviral encephalitis is a very significant human disease and is caused by a large group of viruses distributed across multiple virus families. The virus is introduced to human beings by hematophagous arthropods, mainly mosquitoes and ticks. With a wide spectrum of clini‐ cal manifestations, the diseases are very difficult to diagnose and treat. Although arboviral infections are vaccine preventable and treatable diseases, only a couple of anti-viral thera‐ peutic drugs and vaccines are available. However, several new drugs are undergoing clini‐ cal trials and some will likely become available within 5 years. Animal models that can capture the cardinal features of disease seen in their human counterparts will be a very criti‐ cal technological advance. Using adequate animal models can pave the way for understand‐ ing and uncovering the paramount host and viral factors responsible for breaking down the BBB and leading to the penetration of the virus into the CNS, as well as serving as a good platform to test for effective and preventive modalities.

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