What is the primary causative agent of measles?

The primary causative agent of measles is the rubeola virus, which is a member of the Paramyxoviridae family. This virus is highly contagious and is primarily spread through respiratory droplets when an infected person coughs or sneezes. Understanding the nature of the rubeola virus is crucial for recognizing how measles spreads and why vaccination against it is so important for public health.

Measles is characterized by high fever, cough, runny nose, and a distinctive rash that typically spreads across the body. The rubeola virus can stay in the air and on surfaces for several hours, making it easy for outbreaks to occur, especially in unvaccinated populations. The significance of the rubeola virus in the context of infectious diseases cannot be overstated, as it has led to severe complications such as pneumonia and encephalitis in some cases.

The other options represent different viruses that cause other diseases. Bacillus is a genus of bacteria rather than a virus and is not related to measles. Poliovirus is the causative agent of poliomyelitis, a disease affecting the nervous system. Varicella-zoster virus is responsible for chickenpox and shingles. Therefore, the association of the rubeola virus specifically with