Question

Diseases of brain are hard to treat. When a virus or bacteria infects the brain, it is very difficult to treat and is usually deadly. Why is it so? In the module it is given that parts of central nervous system have high security, then how does the brain get infected?

Answer 1

Our brain, the spinal cord, and its surrounding structures can become infected by a large spectrum of germs. Bacteria and viruses are the most common offenders. Parasites, fungi, and other organisms can infect the central nervous system (CNS).And it is also difficult to detect the brain diseases. So,it is very difficult to treat and is usually deadly. Virus infections usually begin in peripheral tissues and can invade the mammalian nervous system (NS), spreading into the peripheral (PNS) and more rarely the central nervous systems (CNS). The CNS is protected from most virus infections by effective immune responses and multi-layer barriers. However, some viruses enter the NS with high efficiency via the bloodstream or by directly infecting nerves that innervate peripheral tissues, resulting in debilitating direct and immune-mediated pathology. Most viruses in the NS are opportunistic or accidental pathogens, but a few, most notably the alpha herpesviruses and rabies virus, have evolved to enter the NS efficiently and exploit neuronal cell biology. Remarkably, the alpha herpesviruses can establish quiescent infections in the PNS, with rare but often fatal CNS pathology. Here we review how viruses gain access to and spread in the well-protected CNS, with particular emphasis on alpha herpesviruses, which establish and maintain persistent NS infections.