Stroke is a common cause of morbidity and mortality all over the world. According to the American Stroke Association, stroke is a disease that affects the arteries leading to and within the brain. It occurs when an artery carrying oxygen and nutrients to the brain is either blocked by a clot or ruptures. Because of this blockage or rupture, the brain does not get sufficient oxygen and this causes brain cells to die. Strokes that are extremely severe can lead to death.
Stroke and viral infections
As per a study published in the Journal of Stroke in 2013, stroke is one of the leading causes of death and disability in India with a high prevalence in both rural and urban areas. Another study in Infectious Disorders - Drug Targets in 2010 says that while established risk factors such as diabetes, hypertension, high cholesterol and obesity have been identified and are targets for stroke prevention, viral infections are also emerging as risk factors for stroke.
This study indicates that the varicella-zoster virus (VZV) which causes chickenpox and shingles, the human immunodeficiency virus (HIV) and cytomegalovirus (CMV) can cause stroke because they can directly invade cerebral arteries and cause clots, embolisms and blood vessel ruptures.
A study published in JAMA Neurology in July 2020 linked patients with COVID-19 infection to a high risk of ischemic strokes. This shows that the link between viral infections and stroke risk is one that needs further exploration and the development of possible preventive measures and therapies is called for.
A new study published in The Lancet Neurology throws further light by indicating that mosquito-borne viruses such as Zika and chikungunya can also trigger strokes, thereby widening the area of study much further.
Zika, chikungunya and the risk of strokes
The study begins by stating that arthropod-borne viruses, also known as arboviruses, are very common in the tropical areas of the world. Countries like Brazil and India witness the emergence of almost simultaneous outbreaks of malaria, dengue, chikungunya and Zika, indicating that many of these viruses can infect the susceptible at once. In Latin America, Zika and chikungunya outbreaks have also been accompanied by an increase in immune-mediated and neurological diseases.
The researchers conducted an observational study by recruiting 1,410 adults aged 18 years or above referred to the Hospital da Restauracao, Brazil, between 2014 and 2016. These patients were suspected to have an acute neurological disease and a history of suspected arboviral infection and the researchers looked for evidence of Zika, chikungunya or dengue infection by examining viral RNA or specific immunoglobulin M antibodies in their serum. About 201 of these patients had symptoms consistent with an arbovirus infection and were selected for further study.
About 148 of these 201 patients had lab-confirmed evidence of arboviral infection, with 98 patients showing signs of a single infection. Of these 148 patients, 41 had Zika, 55 had chikungunya, two had dengue and 50 had evidence of a dual infection: a deadly combination of Zika and chikungunya. All arboviral patients had a broad range of central nervous system (CNS) and peripheral nervous system (PNS) diseases.
Chikungunya was more often associated with CNS disease like myelitis (inflammation of the spinal cord that can disrupt the connection between the brain and the rest of the body). Zika infection was more associated with PNS disease, especially Guillain-Barre syndrome (an autoimmune disorder where the immune system attacks healthy nerve cells and can eventually lead to paralysis).
Patients with Zika-chikungunya dual infection and Guillain-Barre syndrome had more aggressive disease and required intensive care as well as longer hospital stays, compared to those with mono-infections.
Eight of the total Zika-chikungunya dual infection patients suffered strokes compared to five mono-infection patients with either Zika or chikungunya. This study, therefore, clearly shows that while Zika and chikungunya are individually dangerous diseases that may increase the risk of strokes, this risk is much more severe in the case of patients with dual infection of these arboviruses.
The researchers highlighted that even though the world's attention is focused on COVID-19 and its neurological implications, the risks posed by the co-occurrence pf other viral infections such as Zika and chikungunya should not be ignored.
For more information, read our article on Stroke.
Health articles in Firstpost are written by myUpchar.com, India's first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.