Zika Virus

Introduction

Zika virus (ZIKV) is a member of the Flaviviridae family and was initially identified in the Zika Forest of Uganda, hence its name. It is a mosquito-borne flavivirus and has emerged as a significant public health threat in recent years due to its rapid spread and association with severe neurological complications, particularly in newborns.This blog reviews the epidemiology, transmission dynamics, clinical manifestations and control strategies of Zika virus, highlighting the importance of an integrated approach to combat this disease.

‍

‍Epidemiology

Zika virus was first isolated in 1947 from the serum of a sentinel Rhesus monkey from the Zika Forest (Uganda) during a study on the transmission of yellow fever. It causes sporadic human infections in Africa and Asia. Serological and entomological studies have suggested that ZIKV is widespread throughout these continents. The virus gained international attention during the 2015-2016 epidemic in the Americas, which was linked to increased cases of microcephaly and Guillain-Barré syndrome. On 1st February 2016, the World Health Organization (WHO) declared a global public health emergency due to the ZIKV threat .
‍

India reported an outbreak of ZIKV disease in Kerala State that occurred in July 2021, marking the first outbreak activity in the South-East Asia Region since the cluster in Jaipur, India, in 2018.

Transmission

Zika virus is primarily transmitted through the bite of an infected Aedes mosquito, the same mosquito responsible for spreading dengue, chikungunya, and yellow fever. These day-biting mosquitoes are prevalent in tropical and subtropical regions.

Other modes of transmission include:

• Maternal-fetal transmission: Zika can be transmitted from a pregnant woman to her fetus, leading to congenital Zika syndrome.
• Sexual transmission: The virus can be transmitted through sexual contact, with cases reported of transmission from both symptomatic and asymptomatic individuals.
• Blood transfusion: There have been reports of Zika virus transmission through blood transfusions.
• Laboratory exposure: Occupational exposure in laboratory settings has been documented.

Clinical Manifestations:

Approximately 80% of Zika virus infections are asymptomatic. When symptoms do occur, they are generally mild and include:

• Fever
• Rash
• Conjunctivitis
• Muscle and joint pain
• Headache

Severe complications of the Zika virus include Congenital Zika Syndrome, which can cause microcephaly and brain abnormalities in newborns, and Guillain-Barré Syndrome (GBS), an autoimmune disorder that leads to muscle weakness and paralysis.

Diagnosis

The diagnosis of infection by Zika virus is based on clinical, epidemiological and laboratorial criteria. Because the symptoms of ZIKA disease are nonspecific and can easily be confused with those of other arbovirus-induced diseases, such as dengue and chikungunya, in regions where those viruses cocirculate.

Zika virus infection can be confirmed through:

• RT-PCR (Reverse Transcription Polymerase Chain Reaction): Detects viral RNA in blood, urine, or other body fluids.
• Serological tests: Detect antibodies against Zika virus
• IgG Testing
• Challenges: Cross-reactivity with other flaviviruses, such as dengue, can complicate interpretation. Confirmatory testing (PRNT - Plaque Reduction Neutralization Test) may be required.
• IgM Testing: Useful to assess population-level immunity and to differentiate between recent and past infections.

Control and Prevention

Efforts to control and prevent Zika virus transmission focus on reducing mosquito populations and minimizing human exposure to mosquito bites. Key strategies include:

• Vector control: Vector control involves getting rid of standing water where mosquitoes breed, using insecticides, and employing biological methods like fungi (Metarhizium anisopliae and Beauveria bassiana) to control mosquito populations.
• Personal protection: Using insect repellent, wearing long sleeves and pants, and using mosquito nets.
• Public health campaigns: Educating communities about Zika virus and promoting practices to reduce mosquito exposure.
• Sexual transmission prevention: Advising couples in affected areas to practice safe sex or abstain from sexual activity during pregnancy.

In addition to above mentioned points, research is also in progress to develop vaccines and antiviral treatments for Zika virus. Several vaccines are in various stages of clinical trials, showing promise for future prevention efforts.

Conclusion

Zika virus remains a global health threat due to its potential for rapid spread and severe neurological complications. Comprehensive strategies for vector control, public education, and medical research are essential for mitigating the impact of Zika virus.