Coronavirus: from the cold to respiratory syndromes

The new epidemic in the city of Wuhan in China draws attention again to the coronavirus. A new variant of the virus (Covid-19) appeared in December 2019, associated with 27 cases of very severe pneumonia. The first information, it is likely that all cases were linked to a market for food and live animals. Today, there are more than 70 thousand confirmed cases .

However, it is not the first time that the coronavirus has been linked to major epidemics of severe respiratory infections.

WHAT IS THE CORONAVIRUS?

Coronaviruses are a large group of viruses that are common among animals. Therefore, most strains of coronavirus circulate among animals and do not even infect humans. In rare cases, when animals are transmitted to humans, scientists call them zoonotic. As a result, these cases can cause respiratory illnesses, from a simple cold to severe pneumonia.

Namely, only seven strains of coronavirus out of the existing thousands are transmitted to people

  • Alpha coronavirus 229E and NL63.
  • Beta coronavirus OC43 and HKU1
  • SARS-CoV (causing Severe Acute Respiratory Syndrome or SARS).
  • MERS-CoV (causing Middle East Respiratory Syndrome or MERS).
  • Covid-19

The most common coronaviruses that infect humans are the alpha and beta coronaviruses. They are often associated with common colds and are responsible for mild respiratory diseases that are naturally combated by the immune system itself. These types of viruses are transmitted from person to person and lead to the appearance of typical symptoms of a common cold: runny nose, cough, sore throat, possibly headache and perhaps fever, which can last for a few days.

In contrast, for those with a weakened immune system, such as the elderly, children, pregnant women, transplant patients or HIV carriers, there is a chance that the virus will cause infection in the lower respiratory tract, with much more serious complications, such as pneumonia, bronchitis, syndrome severe acute respiratory failure, kidney failure and even death.

Severe Acute Respiratory Syndrome (SARS)

The first reported case of SARS-CoV infection, which causes Severe Acute Respiratory Syndrome, was in 2002 in Asia. Bats were the most likely source of the virus, which spread to kittens, which were sold in food-making markets . In this way, people who ate the meat of these animals, probably raw or undercooked, were infected. The virus then spread by human-to-human transmission through direct contact.

It was first identified in Guangdong province in southern China. According to the WHO , the main complications are respiratory, but it can also cause diarrhea, fatigue, shortness of breath, difficulty breathing and in addition, kidney failure. Depending on the patient’s age, the SARS mortality rate ranged from 0 to 50% of cases, with the elderly being the most vulnerable.

In conclusion, the virus has spread to 30 other countries, including Hong Kong, Taiwan, Vietnam, Canada and Singapore. Thus, WHO coordinated an international campaign to diagnose, track and contain the disease. It was successfully contained a few months later, after 8,400 cases and about 900 deaths. Since then, no other cases have been reported.

Middle East Respiratory Syndrome (MERS)

The first case of MERS-CoV infection, which caused the Middle East Respiratory Syndrome, was in Saudi Arabia in 2012. In the case of MERS, the virus probably also originated from bats, which passed on to dromedaries and then to humans. The exact way it spread from dromedaries to people is not well known. However, it is known that animal viruses can mutate or combine with other viruses to create new strains that can be transmitted to people.

So far, all reported cases have been linked to countries within or near the Arabian Peninsula. However, the largest known outbreak of MERS outside the Arabian Peninsula occurred in the Republic of Korea in 2015. The outbreak was associated with a traveler who had returned from the Arabian Peninsula.

Namely, the main symptoms are severe respiratory diseases. They usually include fever, cough, shortness of breath and pneumonia. In addition, other symptoms may be: muscle pain, diarrhea, vomiting and nausea. Transmission is through direct contact.

From September 2012 to the end of November 2019, WHO has been notified of 2,494 laboratory-confirmed infections with MERS-CoV and 858 associated deaths.

The New Coronavirus (Covid-19)

The exact origin of Covid-19 has not yet been confirmed, but researchers who analyzed the genetic material identified strong similarities with bat coronaviruses. According to the GISAID platform , the genome of the new coronavirus is 80% identical to the SARS virus, but further away from the MERS virus.

The transmission of Covid-19 to humans has also not been confirmed, it is not clear whether it was transmitted from bats to humans or whether it passed through an intermediate species. According to some scientists, the new coronavirus is the result of viral recombination – a process in which more than one virus infects the same cell at the same time and creates a “recombinant” virus strain.

Not much is known about how Covid-19 spreads. Therefore, current knowledge is largely based on what is known about similar coronaviruses. At first, spread from person to person happens between close and direct contacts. And, like most respiratory viruses, people are considered most contagious when they are most symptomatic.

According to the WHO bulletin of February 11, 2020, there were 43,103 cases reported to date, with 1,017 deaths in China alone. Outside China there are 395 confirmed cases in 24 countries with only 1 death.

 

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