Coronaviruses are large, enveloped and positive-stranded RNA viruses possessing the largest genome (ranging from 27 to 32 kb) among all other RNA viruses infecting birds and mammals. These viruses belong to the family Coronaviridae. The virus derives its name "corona" which in Latin means crown as the spike forms large protrusions from the virus surface giving coronaviruses a crown-like appearance. Different studies conducted on coronaviruses suggest that they are capable of adapting to new environments through mutation and recombination by altering host range and tissue tropism efficiently.

According to the World Health Organization, the first Severe Acute Respiratory Syndrome Corona Virus (SARS-CoV) outbreak occurred in China's Guangdong province, in November 2002 which affect 26 countries and more than 8000 cases with 774 death were seen. SARS-CoV identified as an animal virus in 2003 and animal reservoir is yet uncertain perhaps bats that spread to civet cats and supposed to be jumped in humans by close contact with civet cats and animals. SARS-CoV is transmitted from person to person by close personal contact. It is thought to be transmitted most readily by respiratory droplets which were produced by an infected person while coughing or sneezing. Since 2004 no new cases have been reported but it should not be thought of as eradicated because there is the chance of reemergence as the virus has an animal reservoir.

In 2012 MERS-CoV was identified to be the causative agent of the Middle East respiratory syndrome (MERS). worldwide, nearly 2500 cases of MERS-CoV infection have been reported from 27 countries till 2019 with 850 death. The reservoir of MERS-CoV is believed to be dromedary camels, but the mechanism of transmission from camels to humans is unknown until now. The common mode of transmission includes person to person via direct contact, respiratory droplets (particles > 5 micrometers), or aerosols (particles < 5 micrometers).

CoronaVirus Disease - 19 (COVID-19) is caused by SARS-CoV-2 which stands for Severe Acute Respiratory Syndrome – Corona Virus -2. Initially, this virus was named as 2019-nCoV and further named as SARS-CoV-2 by the International Committee on Taxonomy of Viruses. SARS-CoV-2 was first originated in Wuhan city of China in December 2019 and spread worldwide. COVID-19 disease outbreak was declared a pandemic on 11th March 2020 by the World Health Organization (WHO).

According to the Center for Disease Control (CDC), COVID-19 disease is a type of respiratory disease-causing flu-like symptoms with fever, cough, and shortness of breath. It is a kind of zoonotic viral disease transmitted originally from bats (Primary host) and pangolins or snakes assumed to be of intermediate host whereas humans as a final host.  This disease is transmitted to a human by consumption of meats of those infected animals or through close contact with these animals or their products. Human to human transmission occurs through air droplets and aerosols released by an infected person during sneezing, speaking, coughing, or touching of an infected object. This disease is looming more than 188 countries in the world. According to WHO, on 26 August 2020, more than 23.9 million cases of COVID‑19, 819,000 deaths, more than 15.5 million recovered.

The first COVID-19 positive case was reported in Nepal on 23 January 2020 who had returned to Kathmandu from Wuhan on 9 January. The first case of local transmission was confirmed on 4 April in Kailali District. According to the Ministry of Health and Population (MoHP)  total confirmed cases 33,533 cases, 19,119 recoveries, and 164 deaths in the country. In the meantime, 621,901 PCR tests have been performed in 40 laboratories across the country.

A wide range of symptoms had been reported in COVID-19 patients – ranging from mild symptoms to severe illness. Older adults and diabetes, heart and lungs diseased patients seem to be at higher risk for developing more serious complications from COVID-19 illness. Symptoms may appear 2-14 days after being exposed to the virus. Symptoms may include fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, congestion or runny nose, nausea or vomiting, diarrhea.

The ongoing corona pandemic is causing great loss of life and affecting day to day life also different sectors including health, economic, employment, education, tourism, agriculture, environment have been affected