Human coronaviruses are everywhere and were identified decades ago. Human coronavirus was cultured in the 1960s from nasal cavities of people with the common cold, reports a recent study. They are the 2nd leading cause of the common cold, after rhinoviruses.
People around the world commonly get infected with human coronaviruses 229E, NL63, OC43, and HKU1 say the CDC.
There are four main sub-groupings of coronaviruses, known as alpha, beta, gamma, and delta. Both the Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), are betacoronavirus and have their origins in bats. Both MERS (ongoing) and SARS (2004) have been known to cause severe illness in humans.
Betacoronaviruses are microscopic balls covered in spikes that encapsulate a central core of genetic material. The virus must infect cells in order to replicate, and to do this it must first attach to the cells.
On January 9, 2020, China's CDC reported a novel coronavirus as the causative agent of the new coronavirus outbreak, which is phylogenetically in the SARS-CoV clade. This novel coronavirus has been named ‘severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), while the human disease has been classified by the WHO as COVID-19 disease.
Airborne transmission via droplets and aerosols enables some of these coronaviruses to spread efficiently among humans, causing outbreaks that are difficult to control. Because viruses spread by small particle aerosol do not require close contact, the source of infection may not be evident. These small particles can be inhaled by susceptible persons in the same room or are capable of more distant spread as they are carried in air currents, says the U.S. CDC.
The current outbreak of novel coronavirus SARS-CoV-2 originated in China during 2019 but has now spread internationally, impacting an increasing number of countries. Reported illnesses have ranged from mild to severe cases, some resulting in fatalities, according to previous studies. The SARS-CoV-2 virus causes COVID-19 disease in humans.
Early information from China, South Korea, and Italy, shows that some people are at higher risk of getting very sick from this illness. This includes older adults and people who have serious chronic medical conditions like Heart disease, Diabetes, Lung disease.
About 35% of the first group of adults admitted to New York City hospitals with COVID-19 disease were diagnosed as obese, according to a research letter published in NEJM on April 17, 2020. The median age was 62.2 years, 60.6% were men.
On February 5, 2020, JAMA published a new study from genetic sequencing data, showing this coronavirus shares 79.5% of the genetic sequence with SARS-CoV and has 96.2% homology to a bat coronavirus.
A study published on July 7, 2020, concluded saying 'it is now established that SARS-CoV-2 pre-existing immune reactivity exists to some degree in the general population. It is hypothesized, but not yet proven, that this might be due to immunity to common cold coronaviruses. This might have implications for COVID-19 disease severity, herd immunity, and vaccine development, which still awaits to be addressed with actual data.'
SARS-CoV was the first major novel infectious disease to hit the international community in the 21st century, says the U.S. CDC.
SARS was first reported in Asia in February 2003 and became a notifiable disease in China in mid-April. As of July 2003, the WHO reported 325 cases, and the illness spread to about 24 countries in South America, Europe, and Asia during 2003.
The incubation period for SARS was typically 2 to 7 days, although in some cases, it may be as long as 10 days. In a very small proportion of cases, incubation periods of up to 14 days have been reported.
The WHO estimated that the case fatality ratio of SARS ranges from 0% to 50% depending on the age group affected.
During 2005, a pre-clinical study found chloroquine is effective in inhibiting the infection and spread of SARS CoV in cell culture. Similar studies (2007) describe the role of these proteins in SARS-CoV replication and potential therapeutic strategies aimed at preventing the entry of SARS-CoV into human cells.
The emergence of the betacoronavirus Middle East Respiratory Syndrome (MERS) was first reported in the Kingdom of Saudi Arabia in 2012.
Humans are infected with MERS-CoV from direct or indirect contact with dromedaries. MERS-CoV has demonstrated the ability to transmit between humans. So far, the observed non-sustained human-to-human transmission has occurred mainly in healthcare settings, says the WHO.
Since 2012 through June 1, 2020, the total number of laboratory-confirmed MERS-CoV infection cases confirmed by the WHO is 2,562. with 881 associated fatalities. Countries in or near the Arabian Peninsula that have reported MERS cases, including, but not limited to Bahrain, Iran, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, United Arab Emirates, and Yemen.
Only 2 patients have ever tested positive for MERS-CoV infection in the USA, both during May 2014.
On July 2, 2020, the WHO stated it does not advise special screening at points of entry with regard to this event nor does it currently recommend the application of any travel or trade restrictions.
Relevant Coronavirus Links
Note: This content is sourced from the US CDC, the WHO, research studies, and is reviewed by health professionals, such as Dr. Robert Carlson.