Pathophysiology of Measles

I’ve been stressing the importance of vaccines and I will continue to do so throughout this blog. BUT just for the sake of education, let’s say someone was not vaccinated and exposed to the measles virus... what next? For this post I’ll go into some detail about the pathophysiology of measles- basically, what happens in the body after someone contracts virus.

As we already know, measles is transmitted by respiratory droplets. That is, it’s spread by contact with secretions from the respiratory system: nose, throat and mouth. This may mean airborne contact (a sneeze) or from contact with surfaces that have shared contact with these infected secretions. Airborne transmission is the most frequent mode.

After a person contracts the virus but before they show symptoms they are in the “incubation” period. A person is still infectious to other people during this time... Pretty dangerous since they might not even know they have the virus. The incubation period lasts around 1-2 weeks before symptoms appear. During this period the virus is infecting the cells of the immune system (more specifically, endothelial, epithelial, monocyte and macrophage cells). It first attacks cells of the respiratory tract and then moves on to the lymph nodes. It destroys lymph tissue and enters the bloodstream (called viremia). One in the bloodstream the virus can spread all over the body including the skin and organs such as the kidney, bladder and even the central nervous system (CNS). Once it enters the CNS it can cause swelling and brain damage because of the inflammatory reaction it causes in the brain. It is this condition (encephalitis) that causes most of the devastating and fatal complications of the measles virus. 

1 in 1000 measles cases will experience encephalitis and of those individuals, 25% will have neurodevelopmental problems for the rest of their life and 15% will die from the disease.

Because of the way the virus attacks immune cells in the body, there is a specific course of symptoms that occur. Think: red rash, blotchy spots, runny nose, etc. More on the symptoms next week.

References:

Barinaga, J., Skolnik, P. (2015). Clinical manifestations and diagnosis of measles. Retrieved from http://www-uptodate-com.offcampus.lib.washington.edu/contents/clinical-manifestations-and-diagnosis-of-measles?source=search_result&search=measles&selectedTitle=1~150#H21

Caserta, M. T. (2014). Measles. The Merck Manual. Retrieved from http://www.merckmanuals.com/professional/pediatrics/miscellaneous_viral_infections_in_infants_and_children/measles.html