I hope that you are all doing the best you can in the current circumstances. Not sure how many of you are still able to go to work but in my case we were asked to avoid going to the lab for at least 14 days (since the 16th of March) so this has been my first week working from home. I have to admit that staying home hasn’t been that easy for me especially with these circumstances and the urge to check the news way more frequently than I would normally do to see if something has happened in the last half an hour. So I decided to take a little break from looking at the quite depressing statistics and look into the virus itself, its mechanism of action and the available options we have to fight against it. I know that probably most of you are already getting tired of the topic but I hope that you will be able to find some new information in this blog.
Coronaviruses are a large family of single-stranded RNA viruses (+ssRNA) that can be isolated in different animal species. For reasons yet to be explained, these viruses can cross species barriers and can cause, in humans, illness ranging from the common cold to more severe diseases such as MERS (Middle East respiratory syndrome) and SARS (Severe Acute Respiratory Syndrome). We need to clarify that coronaviruses that circulate among humans are typically benign, and they cause about a quarter of all common cold illnesses. The problem began when the coronaviruses circulating among bats (natural animal reservoir) have mutated just enough to start infecting an intermediate host – the pangolin, an animal that looks like a cross between an anteater and an armadillo. At the end of 2019 the coronavirus mutated again and started causing diseases in humans.
As my fellow ESR Chi has already mentioned in her blog (https://foodsmartphone.blog/2020/02/22/what-happened-during-the-outbreak/), the outbreak of the virus started at the end of 2019 in Wuhan, a city in the Hubei Province of China. It rapidly spread, resulting in an epidemic throughout China, followed by an increasing number of cases in other countries throughout the world. In February 2020, the World Health Organization designated the disease COVID-19, which stands for coronavirus disease 2019. COVID-19 is caused by SARS CoV-2, or severe acute respiratory syndrome coronavirus 2, because it’s genetically similar to the SARS coronavirus which was responsible for the SARS outbreak in 2002.
After performing a full-genome sequencing and phylogenic analysis, scientists have concluded that the coronavirus that causes COVID-19 is a betacoronavirus belonging to the same subgenus as the SARS virus (as well as several bat coronaviruses), but to a different clade. The structure of the receptor-binding gene region is very similar to that of the SARS coronavirus, and the virus has been shown to use the same receptor, the angiotensin-converting enzyme 2 (ACE2), for cell entry. The lungs are the most affected organs by COVID-19 because the enzyme ACE2 is most abundant in the type II alveolar cells of the lungs. In order to connect to the ACE2, the virus uses a special surface glycoprotein called “spike” (hence their crown-like appearance under an electron microscope). The density of ACE2 in each tissue correlates with the severity of the disease in that tissue.
The incubation period for COVID-19 is thought to be within 14 days following exposure, with most cases occurring approximately four to five days after exposure. Pneumonia appears to be the most frequent serious manifestation of infection, characterized primarily by fever, cough, dyspnea, and bilateral infiltrates on chest imaging. There are no specific clinical features that can yet reliably distinguish COVID-19 from other viral respiratory infections. The infection can range from mild to critical depending on the immune response of the individual. Patients with the above mentioned symptoms should undergo testing for SARS-CoV-2 (the virus that causes COVID-19), in addition to testing for other respiratory pathogens (eg, influenza, respiratory syncytial virus).
A collection of a nasopharyngeal swab specimen is performed to test for SARS-CoV-2. Sputum should only be collected from patients with productive cough. After the collection of the sample SARS-CoV-2 RNA is detected by reverse-transcription polymerase chain reaction (RT-PCR). The results of these test are generally available within a few hours to two days depending on the capacities of the laboratories. Scientists are currently making a great effort to develop rapid, on-site (FoodSmartphone-like) diagnostic tools that could significantly decrease the time and costs of the analysis. Due to the fact that the development of a vaccine against the virus will take at least 1 year (vaccines have already been designed and brought into the first phase of testing, which is the safety phase), a number of investigational agents are being explored for antiviral treatment of COVID-19 at the moment and there are several clinical trials for patients to be enrolled in.
Researchers are working on figuring out how the virus is infecting cells and why it causes relatively mild respiratory diseases compared to the related coronavirus, SARS . These mild cases, could be the key to understanding how to prevent more severe COVID-19 infections. Scientists are using a cell culture system that mimics the upper respiratory tract of humans, which helps them to study how the virus replicates in that environment. By understanding some of the processes the virus uses to infect cells in the upper respiratory tract, they might get some hints as to weak points in the life cycle that could be the targets for interventions.
Another interesting approach to vaccine development could be the use of antibodies of people who have survived the infection and there are some studies coming from China that suggest there is some utility to this treatment but it is still unclear for example whether those who have recovered from COVID-19 can become re-infected.
At the moment our main objective is to flatten the epidemic curve (by staying home, avoiding travel and public activities, washing hands etc.) to help decrease the risk of health services being overwhelmed, to allow for better treatment of current cases and to provide more time for a vaccine and a treatment to be developed.
Take care of yourselves and those around you and together we will be able to get through this difficult time!
Wishing you all the best,