COVID-19 stands for CoronaVirus Disease 2019 which is an illness caused by a novel coronavirus which was first identified amid an outbreak of respiratory illness cases in Wuhan City, Hubei Province, China in December, 2019. The belief that COVID-19 is a disease of people at the extremes of age (very young and very old) may be related to the existence of more than one strain of circulating Coronavirus (CV) causing COVID-19 or that the status of human immune system is crucial. Though with few recent occurrences, the issue of age disparity is almost debunked. As a Professor of Immunology, I will lean more towards the second suggestion though there are many un-answered questions about COVID-19. However, the major attributes of CV is ability to rapidly spread and multiply before effective immunity is mounted by the host, thus the pandemicity of COVID-19.
It is known that ageing is associated with causative factors of secondary immunodeficiency condition such as reduced exercise, increased stress, past and con-current infections, non-communicable diseases (diabetes, hypertension, auto-immune disorders), malnutrition, and hormonal imbalance and social life-style (cigarette smoking, alcohol consumption and moderate exercise). All these factors may be linked with severe COVID-19 in elders.
In the young hosts, immune immaturity is the likelihood. Also, genetic make-up must not be ruled out n determining the severity of CV infection.
CV is spread through infectious aerosols containing the virus by breathing, or when someone with the virus sneezes or coughs into their hands which contaminates objects other people touch or when un-infected person(s) breath in air close to an infected patient who sneezes or coughs. CV from these sources attaches to exposed surfaces especially epithelial lining of respiratory system. A good question is “why wont CV penetrate through intact human skin, eye or mouth?” The likely answer is the innate immune factors of these organs which requires further investigation. However in the case of eyes, one may think of feeling the taste of an eye-drop in the mouth after dropping in the eye or the intimate link between the eye,nose and throat!!! After CV attachment and entry into cells, the next step is replication, transcription of the sub-genomic RNAs, translation and assembly of the viral replicase complexes. Thus, blocking attachment or any of these stagesof CV cycle will be effective in the treatment or prevention of COVID-19.
According to literatures, the initial phase of CV replication is accompanied by production of higher levels of pro-inflammatory proteins (especially type 1 interferon and TNF-alpha), antiviral proteins (for the protection of uninfected cells, limit virus spread and enhance macrophage phagocytosis), fever and cough which subsides within few days. The second phase is associated with high fever, hypoxemia and progression to pneumonia-like symptoms despite progressive decline in virus number. During the third phase, there is further decline in virus number and approximately 20 per cent of patients progress to acute respiratory disoders which often result in death. Because of high level of replicating CV at very early stage of infection, production of multiple proteins that inhibit the antiviral protein IFN and programmed death of immune cell call T-lymphocytes, thehost’s anti-viral immune function is made in-effective.
To date, there is no anti-viral therapeutics that specifically target human CV, so treatments are only supportive. In vitro, interferons (IFNs) are only partially effective against coronaviruses. There are significant therapeutic attempts to inhibit viral replication, remove or reduce inflammatory responses and produce antibodies (neutralising type). However, there is hope for vaccine against CV based on the report that the T-lymphocyte response to S protein and other structural proteins (including the M and N proteins), which interacts first with host cells is long-lasting and persistent.
Due to the lack of effective therapeutics or vaccines for now, few measures to control human CV are continous public health education, surveillance system coupled with rapid diagnostic testing, stringent restrictions and quarantine when necessary. Lifestyles which are hygienic and boost immunity should be practised. The composites of anti-corona task force should include concerted efforts and multi-disciplinary approach of health and medical personnel, Non-Governmental Organizations (NGOs), Philantropists, communication experts, behavioural scientists as well as life and social scientists.
Since inflammation is the hallmark of COVID-19 pathogenesis, reducing or stoppage of this process should be included as part of control measures.
The Nigeria Centre for Disease Control (NCDC) is currently coordinating a multisectoral technical group that is assessing and managing COVID-19 in Nigeria. NCDC is in close communication with the World Health Organization (WHO) who is closely monitoring the situation globally. Currently, specialised isolation units with full personal protective equipment (PPEs) are increasing. PPEs are being distributed to all the general hospitals and major primary healthcare facilities. Ambulances and dedicated phone numbers are provided for prompt action but biosafety level-three diagnostic laboratory for CV is limited. Alert is raised to heightened screening measures at all points of entry and institutions not on compulsory duties are closed for now.
The Federal Competition & Consumer Protection Commission (FCCPC) warned suppliers and retailers not to take undue advantage of citizens by hiking the prices of basic safety and protective apparel such as face masks, goggles, latex gloves, sanitizers and anti-bacterial wipes in the wake of the CV outbreak.
For successful management of COVID-19 patients, the task force should be multidisciplinary. The success of the task force and “reward” to patients may encourage “hidden patients” to self-report to health authorities.
Arinola is a professor of Immunology, Department of Immunology, University of Ibadan, Ibadan. He wrote through [email protected]