You probably wonder where the Corona Virus or COVID-19 came from and how the world was infected. Let me tell you. COVID-19 has spread to almost every country in the world since it first appeared in China in late 2019. The disease has struck Europe, the United States and Southeast Asia and has wreaked havoc in Africa and South America. It's terrible, isn't it? Now, this is the chronology. 1)___,the spread of the corona virus around the world is believed to have started from a market in Wuhan, China. This market sold live and dead animals, including fish and birds. 2)___, such markets pose a higher risk of the virus passing from animals to humans due to poor hygiene standards. Although bats are not sold in the Wuhan market, but it may have infected live chickens or other animals sold there. Bats have many zoonotic viruses including Ebola, SARS, and MERS. Corona has a relationship with these viruses. 3)________________, COVID-19 differs from SARS and MERS due to a broad spectrum of the disease. About 80 percent of cases lead to mild infections. In many cases, many people who carry the disease have no symptoms. This makes COVID-19 more difficult to control. 4)______,many people travel to another country and they are very likely to carry the virus and transmit it to others even though they do not feel sick.​