Hello everyone and welcome to this week's blog post, where I will be discussing the Zika virus and how close we are to its eradication. I will begin by exploring what the Zika virus is and how it spreads, before moving onto its recent epidemic and the recent breakthrough in manufacturing a vaccine for the disease.
According to the World Health Organisation, the Zika virus is now present in 70 countries and territories around the world. Zika virus disease, named after the Zika Forest in Uganda where it was first isolated from a monkey in 1947, is a disease mainly spread by Aedes aegypti mosquitoes. While about 80% of people who contract Zika virus disease do not have any symptoms, some people have mild symptoms such as a rash, itching, back pain, and fever-like symptoms such as a high temperature and headache. As such, the disease is not harmful for most people. However, as I will explain, the Zika virus can potentially have catastrophic consequences for pregnant women.
The scientific community have collected enough evidence to prove that the Zika virus causes birth defects in unborn children. The most common birth defect caused by the Zika virus is microcephaly. Babies born with microcephaly can sadly have a whole range of problems, the most common of which being that the baby will have an abnormally small head, resulting in the brain not developing properly. Microcephaly can also lead to seizures, vision loss and hearing damage.
While the symptoms of Zika virus disease have been known for some time, the reasons behind them have only been fully understood since 2017, due to research by the University of Texas. Normally, the brain develops from neural stem cells. Neural stem cells are simple cells which are able to differentiate ('change form') into various types of neural cell, including neurons and glial cells (the cells that surround neurons and provide support and insulation for them). Due to the fact that these stem cells are essential to the growth of the brain, the team at the University of Texas correctly deduced that the Zika virus interfered with the stem cells in the brain during development.
To gather evidence for this hypothesis, the team delved further into the Zika virus and discovered that, while the Zika virus has both an Asian and African lineage, only the Asian lineage has been linked to microcephaly, and as such, the team focused on this group of the virus. They discovered that this group of Zika virus prevented neural stem cells spreading through the brain and differentiating into neural cells, thus preventing the brain from developing. Nevertheless, the researchers did conclude that the effect that the Zika virus had on interfering with neural stem cell proliferation in the brain differed depending on the particular strain of Zika virus studied, due to the slightly different proteins that are synthesised by each strain.
Unfortunately, there are no current treatments for Zika virus disease, however, according to the National Health Service, drinking lots of water and taking paracetamol may help reduce the symptoms. Moreover, they also suggest that, if you think that you have been infected with the Zika virus and are in a Zika-prone area, that you get tested for malaria as they have similar symptoms.
Due to the recent Zika virus epidemics, including in Oceania between 2013-2014 and the current epidemic in the Americas, which first originated in 2015, there has been lots of pressure on scientists to develop a vaccination for the disease. After years of research, on 11 December 2019, researchers at the University of Adelaide in Australia published their research into producing vaccination for the disease, which many lay the ground stones for the global eradication of the disease.
In their study, the researchers discovered that a T cell-based vaccine was incredibly effective in protection against infection from the Zika virus. T cells are one of the major components of the active immune system. Indeed, they are critical in mounting a defence against pathogens. As such, T-cell vaccines help induce cellular immunity (an immune response that doesn't utilise antibodies) by promoting the production of these protective T cells, thus ensuring that the Zika virus is destroyed.
This new approach at producing a vaccine for the Zika virus is very significant as it suggests that, in the future, we should focus on developing T-cell based vaccines, instead of antibody-based vaccines, for related diseases such as dengue virus and yellow fever. Nonetheless, this vaccine has only just entered phase 1 of clinical trials (the vaccine is tested on humans for the first time), and as such is still very far away from being approved for use by the FDA.
In conclusion, I would contend that we still have a long way to go before the Zika virus can be eradicated. This is because it was only in March 2017 that the first Zika virus vaccine entered phase 2 trials (out of 4 phases). As such, we are still many years away from any Zika vaccine being licensed for medical use. Furthermore, while the Zika virus is extremely dangerous for unborn babies, as it does not result in serious symptoms in most people, it is unlikely that the disease will be eradicated. This is because to eradicate a disease, you need to vaccinate enough people against it to create herd immunity and without serious symptoms, it is unlikely that many people will choose to have the vaccine. Nevertheless, the knowledge gathered in the latest vaccine trials could be utilised for the production of dengue fever and yellow fever vaccines, which could save many humans lives in the future.
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