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Covid-19, MERS, SARS, Flu, And Pneumonia: What Are The Differences?

The coronavirus (Covid-19), which reportedly originated from a wet market in Hubei Province, China, has claimed more than 7,100 lives globally and spread to more than 140 countries since the outbreak started at the end of 2019. The new strain of the coronavirus has triggered global panic and forced several countries like France, Italy, and Malaysia to impose their own lockdowns to prevent the infection from spreading further. Here are the facts people need to know about Covid-19, the flu, common cold, Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS), and pneumonia.

COVID-19, SARS, And MERS Are Also Types of Coronaviruses

The new coronavirus reportedly started in the Huanan Seafood Wholesale Market. There are contradicting statements from Chinese authorities and experts related to the origin of the disease.

According to Chinese authorities, the outbreak began on December 31, 2019, and many of the first cases of the respiratory-related illness were from the seafood market that also sells wild animals in Wuhan. However, Chinese experts claimed that the first new Corona-infected patient which was reported in early December 2019  had no contact with that market, as research published in Lancet indicated.

“No epidemiological link was found between the first patient and later cases,” the study stated. Their data also revealed that, in total, 13 of the 41 cases had not been associated with the market.

Covid-19, SARS, and MERS Started From Animals

Like Covid-19, SARS, and MERS also emerged from animals. SARS was believed to have come from bats. Eighty-seven percent of SARS cases were in Hong Kong and China during the 2002-2003 period. The SARS outbreak claimed 774 lives and infected around 8,000 people globally.

The first MERS cases were reported in Saudi Arabia in 2012. Scientists assume that MERS originated from dromedary camels, either from close exposure to them or consuming camels’ milk.

Bats are sources of coronaviruses. However, further studies are necessary to confirm this hypothesis. Speaking of COVID-19, bats are to blame for the outbreak. However, other research shows snakes and pangolins are the main culprits of the pandemic.

MERS Has The Highest Mortality Rate

MERS has the highest mortality rate of all three illnesses (34 percent). Experts at the Center Of Disease Control and Prevention (CDC) said 3 or 4 out of 10 MERS-infected patients cannot live longer. Eighty percent of MERS cases were in Saudi Arabia.

As of March 15, Covid-19 had infected 159,623 people globally and killed 5,960 others. However, 75,956 people have recovered, meaning that the recovery rate had reached 47.6 percent compared to the mortality rate (3.7 percent).

“So the mortality rate of Covid-19 at this time is around 3% overall. It’s much higher among older patients. In terms of its spread, we are talking about the number of people that one infected person will infect themselves. At this time, it appears to be about 2.5 people per infected person for Covid-19. This is much less than diseases that are highly communicable like measles but similar to other coronaviruses like SARS,” Dr. Jennifer Horney, Ph.D., MPH, an epidemiologist at University of Delaware, told InsideOver during the panel.

Symptoms and Incubation Periods

The most common signs of Covid-19 are having a high body temperature (38 degrees Celsius), cough, sore throat, and shortness of breath, almost similar to other respiratory illnesses. However, according to the World Health Organization (WHO), in some infected cases, more severe Covid-19 diseases can cause kidney failure and acute respiratory syndrome.

A study published in Science showed that 86 percent of Covid-19 infections before January 23 were undetected as they showed no symptoms, leading to a rapid spread in Wuhan.

Dr. W. Graham Carlos MD, a practicing pulmonary and critical care physician in the Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine Indiana University School of Medicine, said in an expert panel on Covid-19 hosted by Newswise that people tested positive for Covid-19 do not always have a fever in the early stages, making it difficult to judge based on that symptom alone. An Indonesian working for the Diamond Princess cruise ship was tested positive for Covid-19 without showing any symptoms at all.

The MERS incubation period is 2-14 days (the median incubation period is five days). In comparison, the SARS incubation period is 1-14 days (the median incubation is 4-5 days), and the Covid-19 incubation period is 1-14 days.

Human-to-human transmission in SARS and Covid-19 is more rapid than that of MERS. COVID-19 can spread through droplets in people’s coughs and sneezes.

Covid-19 vs. Flu vs. Cold

People may get confused with these three sicknesses. One of the most obvious symptoms of the flu is the runny nose (besides fever, muscle pain, sore throat, and cough). The flu usually comes suddenly while the cold strikes in stages. However, the flu is now always followed by fever.

Covid-19’s human-to-human transmission occurs through droplets from sneezing and coughing. The droplets are still on the surface even though the person is not near.

“It’s important for us to distinguish between Covid-19 and influenza,” said William Curry, M.D., associate dean of UAB’s (University of Alabama Birmingham) primary care and rural medicine, adding that: “This will become apparent with shortness of breath.”


Pneumonia has similar symptoms to the flu, such as fever, chilling cough, and loss of appetite. However, pneumonia does not worsen rapidly, as Paras Lakhani, a radiologist at Thomas Jefferson University, told Business Insider. Also, it is tricky to diagnose pneumonia, given the symptoms may vary.

“Pneumonia usually doesn’t rapidly progress. Typically, most hospitals will treat with antibiotics, and patients will stabilize and then start to get better,” Lakhani said.

Pneumonia is an infection on a lung’s air sacs (alveoli). The pouches may be filled with fluid that can halt breathing and cause a deep cough.