The news is full of stories on the recent outbreak in Wuhan, China. The problem with this kind of hot news story, is that the science is often lost to eye-catching headlines that are meant to thrill and frighten the reader. It's difficult to distill out the cold hard facts , and that's what I hope to do here.
So first things first, what is this virus.
First off, terminology is important. The virus thought to be responsible for this particular outbreak is a member of a family of viruses called Coronaviridae, or coronaviruses. This particular virus is not "THE" Coronavirus, and it has been named 2019-nCoV by the researchers that just published its sequence (not the catchiest of names, but what can you do). (*note 03/11/20: COVID-19 is now the agreed upon name of this virus *) Actually, most of us are intimately acquainted with coronaviruses, as they are the cause of many seasonal viral infections. Thankfully, most of us are less acquainted with the more virulent members of this family, SARS and MERS.
Coronaviruses are single strand, positive sense RNA viruses.
Okay, that's a lot of virology terminology even for me!
So let me break it down. Viruses are micro-organisms which consist little more than their genetic information surrounded by a protective membrane. When viewed under an electron microscope, the membrane of the coronavirus looks like the halo of light around the sun, or solar corona.
Understandably, being that simple and small, viruses are dependent on a host cell to survive. Whereas our genetic information is stored in two strands of DNA, the coronavirus has a single strand RNA genome. The "positive sense" part refers to the information on that RNA. It is immediately available to be decoded into proteins, unlike the other type of RNA virus, "negative sense", which needs to be converted into positive sense RNA before it can make viral proteins.
Okay, stick with me. I wanted to cover all my terminology bases first, so let's jump out of the molecular jargon and get to transmission.
Coronavirus generally spread from person to person through close contact and respiratory droplets. This is why it is so important during cold and flu season to wash your hands and avoid touching your face. It's still the early days of understanding this virus, but if it is like the coronaviruses responsible for seasonal colds or even SARS/MERS, it is spread through this route.
As this is an new virus, it is interesting to determine where it originated. Researchers in Wuhan have just published results from 9 patients infected with this new virus. The researchers obtained bronchoalveolar fluid (BAL) from these patients. BAL is obtained by flushing the lungs with warm fluid and collecting this fluid, which will now contain cells and pathogens that reside in the patient's lungs. The BAL of 2019-nCoV patients contained a virus, that when sequenced, resembled known sequences for 2 bat specific viruses. It was slightly less similar to SARS and MERS.
The similarity to bat viruses has caused an interesting hysteria unique to the internet age. Last week, my feeds were full of images of bats resting in soup.
While direct transmission from bats isn't unimaginable, it is highly unlikely in this case. The initial outbreak of the virus is associated with an open air market in Wuhan, which reportedly does not sell bats. Therefore, it is more likely that there was transmission of the bat virus into another species, which was then transmitted to humans. This was the case with SARS, which was thought to originate with bats which was then transferred to humans through civet cats; and MERS which went through a similar route but through camels. When the virus moves from one species to another, it changes a bit, keeping certain parts of its genetic information, and adapting others. In this way we get "new" viruses.
Coronaviruses primarily infect the upper respiratory tract. The seasonal cold varieties stay in the upper respiratory tract and cause general cold symptoms: stuffy nose, fever, cough, sore throat,etc. Where this current coronavirus, as well as SARS and MERS, differ is the severity of symptoms they cause and the tendency for these symptoms to result in pneumonia. While normal healthy adults are able to fight off the infection; it is the elderly, very young, and immuno-compromised that are at high risk for progressing to these severe symptoms. The common feature of these 3 groups is they all have immune systems which are not equipt to fight the infection, but this is not unique to 2019-nCoV. These three groups are at higher risk for developing severe reactions to most infectious diseases, including influenza, making it important for people to get the seasonal flu vaccine even if they aren't at high risk (it's called herd immunity, and I'll make a post about it later).
In the past coronaviruses have not been successfully targeted by vaccines, therefore the best measure to prevent the spread has been control. While this story has been rapidly developing, it is also clear that measures are being taken to control the spread of the virus. It is not unexpected that cases of infected individuals outside of China are now being reported. As with seasonal cold viruses, transmission of the virus usually occurs before the patient displays symptoms. But, with growing awareness of the virus, preventative measures to contain individuals who have potentially been exposed, is happening now. The SARS outbreak of 2003 lasted approximately 6 months, and we can hope that the current preventative measures will end this outbreak even sooner.
Sources:
Huang, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020 Jan 24. pii: S0140-6736(20)30183-5 ( https://www.ncbi.nlm.nih.gov/pubmed/31986264 )
Fehr, Anthony R, and Stanley Perlman.
“Coronaviruses: an overview of their replication and pathogenesis.” Methods in molecular biology
(Clifton, N.J.) vol. 1282 (2015): 1-23. doi:10.1007/978-1-4939-2438-7_1
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