New Viruses
Function Analysis
A virus can be defined as (defining) an infectious agent which can multiply in plants and animals. Viruses are similar to bacteria in that (comparing) they are tiny but the difference is that (contrasting) bacteria are living organisms whereas (contrasting) viruses are not. It's estimated that approximately (approximating) 30 new viruses have appeared in the past 20 years. Some are extremely dangerous such as HIV and Ebola virus. Both HIV and Ebola (comparing) come from Africa. On the other hand, (contrasting) they are very different in the speed with which they attack human beings: HIV may take 4 to 10 years to kill but Ebola does the job in a few days or weeks. Fortunately, (evaluating) these viruses are not transmitted through the air like influenza. But an airborne virus like Ebola could appear at any time. That's why (reasoning) research into these viruses must be carried out to prevent millions of deaths.