The emerging human coronaviruses: an overview

Coronaviruses belong to family Nidovirus, that are typically capable of affecting the respiratory system of animals, as well as humans. These viruses are common around the globe and are associated with the common colds, upper throat infection, Severe Acute Respiratory Syndrome (SARS), and pneumonia with effect on G.I.T as well.

The emerging human  coronaviruses

Coronaviruses are known to cause significant percentage of common colds (15 to 30 percentage) and studies have revealed that these virsuses primarily infect rats, mice, cats, dogs, turkeys, horses, cattle and pigs as well as humans.

In 1937, for the very first time, the Coronavirus was isolated from poultry stock that was infected with an infectious bronchitis virus. This article will cover different human coronaviruses, their symptoms, transmission, possible treatments, prevention strategies and particularly two dangerous diseases SARS and MERS, caused by coronaviruses.

Facts about Coronoviruses:

Some fast facts about coronaviruses are,

  • Common cold has no cure.
  • Coronaviruses infect many different animal species.
  • Human coronaviruses are six in number.
  • A coronavirus causes both SARS and MERS.
  • SARS from China caused infection in 37 countries and killed 774 people.
  • In Korea, MERS-CoV caused the largest outbreak so far that killed 36 people.

What are coronaviruses?

Coronaviruses are single stranded enveloped viruses with a nucleocapsid of helical symmetry, having the largest RNA genome of any virus with length varies between 26 to 32 kb. They get their name because their surfaces contain the crown-like projections. “Corona” is Latin word that means “crown.” or “halo.”

Many coronaviruses infect many different animal species including camels and bats but rarely the humans. In the 1960s, Human coronaviruses (HCoV) were identified first time in the nasal cavities of patients infecting with common cold. Most often, they attack the humans during cold season of the year especially in winter and early months of spring.

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It is very common for an individual to get cold caused by this contagious coronavirus and then it attacks again after about four months. This happens due to short life span of coronavirus antibodies and because these antibodies are not useful against other strains of coronaviruses.

Types:

Currently, six recognized kinds of strains of coronavirus are known that can infect humans and make them sick. They are categorized differently on the basis of severity of illness and other respiratory signs they cause in humans. They are found in 2 genera:

  • Alpha coronaviruses (HCoV-229E and HCoV-NL63)
  • Beta coronaviruses (HCoV-OC43 and HCoV-HKU1)

And more dangerously the SARS-CoV strain that causes  respiratory illness known as Severe Acute Respiratory Syndrome (SARS) and an additional novel betacoronavirus, MERS-CoV that is identified in 2012 and is responsible for Middle East Respiratory Syndrome (MERS). HCoV-229E and HCoV-OC43 strains are responsible for a significant share of common colds.

  • SARS:

Severe Acute Respiratory Syndrome (SARS) is a dreadful contagious disease that is caused by a novel strain of coronavirus named as SARS-CoV coronavirus that was identified in 2003. It can lead to life-threatening form of pneumonia therefore it has great economic and medical concern. The first epidemic started in the Guangdong province of South China in November 2002, from where it reached to Hong Kong and eventually spread to 37 countries.

SARS-CoV is unique in nature because it can cause infection both in the upper and lower respiratory portion and can lead to gastroenteritis. SARS symptoms develop for a week in the patients and start with a fever. During initial phase, flu-like symptoms appear such as dry coughing, breathlessness, chills, diarrhea, aches and pneumonia may develop afterward.

During the advance stage of the disease, SARS may become responsible for the failure of heart, liver or lungs. According to epidemiological data, there were 8,098 SARS cases with death of 774 people, thus having 9.6 percent mortality rate.

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Older adult people were more susceptible to these complications and among diseased people, half of the infected people having age over 65 years did not survive. Then in July 2003, eventually this disease was brought under control.

  • MERS:

Potentially MERS-CoV is a fatal novel strain that was first identified in humans in 2012 and causes a dreadful respiratory disease named as Middle East Respiratory Syndrome (MERS). MERS was first reported in Saudi Arabia in 2012 and since the it has spread and caused infection in the people of more than 25 countries including U.S.

MERS outbreak occurred in Korea in May 2015, which was considered as the largest outbreak till now outside of the Arabian Peninsula. This illness includes common symptoms like fever, coughing, breathlessness and associated symptoms such as chest pain, chills, sore throat, headache, malaise, nausea, diarrhea or vomiting. This emerging respiratory disease transfers via close contact with infected people.

However, mostly the reported MERS cases were belonged to those individuals who had tour of Arabian Peninsula. MERS is considered as fatal disease and causing mortality in 30 to 40 percent of individuals, who contract it. Due to these outbreaks, more than 475 infected people have died from Middle East Respiratory Syndrome (MERS).

Symptoms:

Coronavirus usually involves in cold or flu-like symptoms and other respiratory tract infections. After coronavirus infection, these symptoms appear and are typically mild.

Symptoms include:

  • runny nose
  • sneezing
  • cough
  • fatigue
  • sore throat
  • fever (in rare cases)
  • exacerbated asthma

Like coronavirus, rhinovirus is also responsible for the common cold but unlike rhinoviruses, it is very difficult to cultivate the human coronaviruses in the laboratory. That is why the coronavirus has more impact on national economies and public health.

Transmission:

It is believed that this coronavirus transmission occurs through fluid particles secreted from the respiratory tract. There are following ways that are adopted by coronavirus to spread:

  • Sneezing and coughing from uncovered mouth and nose can sprinkle the fluid droplets into air, thus disseminating the infection.
  • Hand shaking and coming in touch with a person infected with coronavirus can transfer the virus among persons.
  • Having physical contact with object such as doorknobs containing the virus and after that touching your eyes, mouth, or nose.
  • Rarely, a coronavirus transmission may occur through contact with faeces.
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On the basis of mutating abilities of the coronavirus, it is considered as so contagious. The disease occurs mostly during cold months but is still present during the rest months of the year.

Most people get coronavirus infection at least once in their lives. Young individuals are most likely to come in contact with coronavirus, and people can be attacked with this infection more than one time over the lifetime course.

Treatment:

Unfortunately, there is no cure of coronavirus infection and there is no recommended antiviral medicine. So, treatment of coronavirus includes taking care of yourself, supportive medication and over-the-counter (OTC) medication:

  • Take bed rest and avoid overexertion.
  • Take plenty of water.
  • Keep yourself away from smoky areas and do not smoke.
  • Take medicines like naproxen, ibuprofen, acetaminophen to reduce pain and fever.
  • Use a cool mist vaporizer or a clean humidifier.

Prevention Strategies:

To prevent coronavirus infection, keep stay in bedroom and take rest during appearance of symptoms. Don’t make close contact with affected persons.

During sneezing and coughing, the covering of nose and mouth with a handkerchief or tissue can stop the spread of infection. Discard any used handkerchief or tissue, keep yourself clean and maintain hygiene around the living area.

Authors: Qaisar Tanveer1, Muhammad Naeem Faisal1 and Muhammad Jawad Aslam1

1Institute of Pharmacy, Physiology and Pharmacology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, Pakistan.

Corresponding Author E-mail: saaimtanveerrandhawa@yahoo.com

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