The mosquito responsible for transmitting Japanese encephalitis, known as the ‘small red house mosquito,’ is overall dark brown, lacks distinct patterns, and features a broad white band in the middle of its proboscis. This information is provided by the Korea Disease Control and Prevention Agency.
A study has revealed that the ‘Japanese encephalitis virus type 5’, previously reported only in Korea, is more lethal than the existing type 3 virus, making it challenging to provide effective protection with currently available vaccines.
The Basic Medical Research Promotion Team of the Catholic Medical Center, led by Professor Sang-Wook Seo and Dr. A-Ra Lee, announced on the 5th that they analyzed the characteristics of the Japanese encephalitis virus type 5 prevalent in Korea, publishing their findings in the international journal ‘Emerging Microbes & Infections.’ The research team utilized an experimental animal model for their analysis, using a domestic isolate provided by the National Pathogen Resource Bank of the Korea Disease Control and Prevention Agency.
The Japanese encephalitis virus type 5 is a newly identified virus that has been reported only in Korea since 2010. While no cases have been reported in other countries, neighboring regions where Japanese encephalitis is common are monitoring the spread of the type 5 virus, especially after it was found to be similar to viruses previously isolated in Malaysia and China. Japanese encephalitis is an infectious disease that has primarily affected Asia and Australia since it was first documented in Japan in 1924 and is mainly transmitted by mosquitoes. Although over 99% of infections are asymptomatic, encephalitis symptoms can develop in some patients, leading to a mortality rate as high as 30%. Furthermore, 30-50% of those who recover may experience lasting effects, such as mental and physical disabilities, including neurological disorders. In Korea, vaccination against the previously prevalent type 3 virus is ongoing, but there is an increasing need for measures to prevent the spread of types 5 and 1, which have been rising recently.
The research team analyzed the ‘NCCP 43279 virus’, a type 5 virus isolated from a patient with Japanese encephalitis in 2015, and reported that it has a higher mortality rate and pathogenicity than the type 3 virus. Furthermore, while the current Japanese encephalitis vaccine is effective in blocking viruses like type 3 due to differences in virus surface proteins, it is less effective against the type 5 virus. This discrepancy likely explains the continued detection of the type 5 virus since 2010, despite the inclusion of the Japanese encephalitis vaccine in Korea’s national immunization program. Professor Seo Sang-wook stated, “As the number of domestic Japanese encephalitis cases has increased since 2010, ongoing isolation and research on various virus types, including type 5 Japanese encephalitis virus, are essential,” adding, “Based on the results of this study, the urgent development of a new vaccine targeting type 5 Japanese encephalitis virus is needed.”
Understanding Japanese Encephalitis Virus Type 5: Risks and Research Findings
The mosquito species responsible for transmitting Japanese encephalitis is commonly known as the ‘small red house mosquito’. This insect is characterized by its dark brown body and distinct wide white band in the center of its proboscis, making it a notable vector of the virus.
The Emergence of Japanese Encephalitis Virus Type 5
According to a groundbreaking study, the Japanese encephalitis virus type 5 (JEV-5), which has only been identified in Korea, poses a significant risk; it is found to be more lethal than the previously predominant strain, type 3. This alarming conclusion was reached by researchers at the Catholic Medical Center’s Basic Medical Research Promotion Team, led by Professor Sang-Wook Seo and Dr. A-Ra Lee. Their findings were published in the international academic journal Emerging Microbes & Infections.
The research involved a thorough analysis utilizing an experimental animal model and a domestic isolate provided by the National Pathogen Resource Bank of the Korea Disease Control and Prevention Agency.
Key Findings about JEV-5
The emergence of JEV-5 is noteworthy, as it has only been reported since 2010, and no cases have been documented in other countries thus far. However, the neighboring regions, where Japanese encephalitis is prevalent, are on high alert regarding the spread of JEV-5 due to its similarity to viruses found in Malaysia and China.
- Asymptomatic Infection: More than 99% of individuals infected with the Japanese encephalitis virus remain asymptomatic.
- Severe Cases: If symptoms progress to encephalitis, the mortality rate can escalate to as high as 30%.
- Long-term Aftereffects: 30-50% of patients who recover may suffer from serious aftereffects, including neurological disorders.
Vaccination Efforts and New Challenges
In Korea, vaccination efforts have primarily targeted the JEV type 3 virus. However, with the emergence of type 5, there is an urgent need for enhanced preventive measures to combat the increasing incidences of JEV-5 and type 1. The research team analyzed the NCCP 43279 virus, a type 5 virus isolated from a Japanese encephalitis patient in 2015, discovering it to be more lethal and pathogenic in comparison to type 3.
Crucially, the current vaccination provides effective protection against type 3 but appears less effective against the JEV-5 due to differences in the virus’s surface proteins. This may explain the persistent detection of JEV-5 since its emergence, despite established vaccination programs in Korea.
Expert Insights on JEV-5
Professor Seo Sang-wook emphasized the increasing number of cases of domestically acquired Japanese encephalitis since 2010. He urged the necessity for ongoing isolation and investigation of various virus types, especially JEV-5. He stated, “Based on the results of this study, it is urgent to develop a new vaccine targeting type 5 Japanese encephalitis virus.”
Practical Tips for Prevention
While the development of a vaccine specifically for JEV-5 is underway, there are several practical measures individuals can take to reduce exposure to mosquito bites and thereby decrease the risk of infection:
- Use Insect Repellent: Apply mosquito repellent containing DEET, picaridin, or oil of lemon eucalyptus.
- Wear Protective Clothing: Opt for long sleeves, long pants, and socks to minimize skin exposure.
- Install Screens: Ensure that windows and doors have functional screens to keep mosquitoes out.
- Avoid Peak Mosquito Hours: Limit outdoor activities during dawn and dusk when mosquitoes are most active.
- Eliminate Standing Water: Regularly check your property for standing water and eliminate any potential mosquito breeding sites.
Global Perspective on Japanese Encephalitis
Geographical Distribution
| Region | Notable Facts |
|---|---|
| Asia | Primary region where Japanese encephalitis cases have been reported. |
| Australia | Outbreaks, though less common, have been noted. |
| Europe & Americas | Rarely reported, primarily examined in returning travelers. |
Comparison of Virus Types
| Virus Type | Year Identified | Mortal Cases |
|---|---|---|
| Type 3 | Up to 2010 | 30% |
| Type 5 | 2010 | More than Type 3 |
Future Directions in Research
As research progresses, identifying the genetic and epidemiological characteristics of JEV-5 will be critical for developing effective vaccines and therapeutic options. Continuous monitoring, public education on prevention practices, and regional health policies are fundamental components in addressing this emerging health threat.
The emergence of Japanese encephalitis virus type 5 underscores the need for vigilance in mosquito control and vaccination efforts to safeguard public health. Ongoing research, combined with proactive preventive measures, is essential to mitigate the risks associated with this serious viral infection.
