This short document covers all the types of coronaviruses that exist in nature, the specific one that has caused the epidemic and the mutations that being caused in its genome.

1. Coronaviruses
Types of coronaviruses
There are mainly 7 types of coronaviruses affecting humans out of
which 4 are common i.e. 229E, NL63, OC43, and HKU1 and produce
mild symptoms akin to common cold like:
 Runny nose
 Sore throat
 Headache
 Fever
 Cough
 General feeling of being unwell
While 3 are rare, resulting in mild to severe symptoms. These are
SARS-CoV, MERS-CoV and SARS-CoV-2 (novel coronavirus).
Until 2002, they were considered only minor pathogens of humans.
However an outbreak of severe acute respiratory syndrome (SARS)
that began in China in 2002 was linked to infection with a new CoV
(SARS-CoV). Fever, dry cough, headache, muscle aches and difficulty
breathing were found as symptoms. In 2014, a distinct coronavirus
was isolated in connection with an outbreak of severe respiratory
disease in the Middle East. This virus, called Middle East respiratory
syndrome coronavirus (MERS-CoV), continues to cause sporadic
cases of severe respiratory illness with symptoms like fever, cough,
shortness of breath, nausea, vomiting and diarrhea. SARS-CoV-2
causes COVID-19. This new coronavirus appeared in Wuhan, China,
in late December 2019 after health officials noticed an increase in
pneumonia cases with no known cause. Within a few months, SARS-
CoV-2 has spread to hundreds of countries around the world after
being transmitted through person-to-person contact. Its symptoms
include:

2.  Cough
 Fever
 Shortness of breath
 Fatigue
 Sore throat
 Nasal congestion
 Muscle aches and pains
 Diarrhea
 Loss of taste or smell
 Headache
 Chills (may sometimes occur alongside repeated shaking)
COVID-19 might feel different than symptoms of a cold, the flu, or
allergies. In addition, not everyone with a SARS-CoV-2 infection has
symptoms.
Strains of SARS-CoV-2
Currently, there are 11 types of the virus of which type-O is the
ancestral type that was originally reported from China. One or a few
mutations define the signature of each of these types. Scientists at
National Institute of Biomedical Genomics found in most regions only
one type (A2a) of Covid-19 has begun to overtake other types. By
March-end, the A2a type had nearly replaced all other types and
became the dominant type of Covid-19 all over the world. Out of the
3600 samples they studied, 35 were Indians.
The 35 viral sequences belonged to 4 types: the ancestral type-O (5),
and derived types A2a (16), A3 (13) and B (1). Two types – A3 and
A2a – predominate. All persons infected with type A3 coronavirus
have travel history to Iran, while most persons with type A2a have no
known travel history to countries outside of India. Therefore, the A2a
type is also increasing in its population size within India.
Less common

3. Following is the genome of the SARS-CoV-2 as it originated in Wuhan.
Next is the genome of one of the first cases whose genome was
sequenced in January.
Outside of Wuhan, that same mutation has been found in a sample
which was collected seven weeks later and 600 miles south in
Guangzhou, China.
As the virus spread, the first case in the US also came up.

4. The genome of his virus contained three single-letter mutations also
found in viruses in China. They allowed scientists to trace the man’s
infection to its source.
Five weeks later, a high school student near Seattle tested positive.
Scientists sequenced the genome of his sample and found it shared
the same distinctive mutations found in the first case in Washington,
but also bore three additional mutations. This suggested that the
student did not acquire the coronavirus from someone who had
recently arrived from another country. Instead, the coronavirus was
probably circulating undetected in the Seattle area for about five
weeks.
Washington links then appeared in cases around the world, including
in the Diamond Princess.
Genome of a case in California with no history of travel surfaced,
indicating the virus was already in the community. It did not show
mutations of the Washinton state, rather it had gotten to California

5. through a separate introduction from China.
Two healthcare workers who cared for the patient and their sample
had additional mutations.
The first confirmed case of Covid-19 in New York was announced on
March 1, after a woman living in Manhattan was infected while
visiting Iran. Her genomic mutations indicated that it was not part of
the existing transmission chain.
Dozens of Guatemalans sent on deportation flights from the U.S. later
tested positive for the virus, and coronaviruses carrying mutations
that arose in Europe have been reintroduced to Asia.

6. At this point in the pandemic, coronavirus genomes with 10 or fewer
mutations are common, and only a small number have over 20
mutations — which is still less than a tenth of a percent of the
genome.
The following graphical representation indicates how certain
mutations could be tolerable in the RNA while others would easily
result in changes. In fact, researchers have found that the coronavirus
is mutating relatively slowly compared to some other RNA viruses, in
part because virus proteins acting as proofreaders are able to fix
some mistakes.