In Hubei province China, in December 2019, a virus emerged which would change our lives. Originating from the Wet Markets or a Lab in Wuhan, this virus known as Covid-19 or Coronavirus, had a transmissibility that would come to affect every single individual on a global scale.
So almost a year to the the day of the emergence of this novel virus, what do we know from the vast array of Medical studies and literature.
Published literature can trace the beginning of symptomatic individuals back to the start of December 2019. Following evidence of delayed reporting and attempts to cover up early cases, Chinese authorities eventually announced that a new Respiratory virus was spreading thru the City of Wuhan.
On February 11, 2020, the WHO Director-General, Dr Tedros, announced that the disease caused by a new CoV was COVID-19. Subsequently, the virus was known as SARS-CoV-2 virus.
On March 11, as the number of COVID-19 cases outside China had increased 13 times and the number of countries involved tripled with more than 118,000 cases in 114 countries and over 4,000 deaths, WHO declared the COVID-19 a pandemic.
Although over time the lethality rate of COVID-19 has been significantly lower than that of the SARS and MERS epidemics, the transmission of the SARS-CoV-2 virus is much larger than that of the previous viruses, with a higher total number of deaths. It has been estimated that about one in five individuals worldwide could be at increased risk of severe COVID-19 disease if they become infected, due to underlying health conditions.
As of December the 3rd 2020, there are 65 million reported cases, with 1.5 million reported deaths.
The pathogenic mechanism that produces pneumonia seems to be particularly complex. Viral infection is capable of producing an excessive immune reaction in the host.
The effect is extensive tissue damage with dysfunctional coagulation, with the defined syndrome of MicroCLOTS (microvascular COVID-19 lung vessels obstructive thromboinflammatory syndrome)
The clinical spectrum of COVID-19 varies from asymptomatic or paucisymptomatic forms to clinical conditions characterized by respiratory failure that necessitates mechanical ventilation and support in an ICU, to multiorgan and systemic manifestations in terms of sepsis, septic shock, and multiple organ dysfunction syndromes (MODS).
Early Studies and What We Learned
The early studies shaped our understanding of coronavirus in terms of who it affected and how comorbidities affected outcomes and severity of disease.
Huang et al. illustrated that symptomatic patients (n. 41) suffered from
dry cough, and
Clinical data from the Chinese CDC regarding 72,314 cases, were shared in JAMA, providing the first important illustration of the epidemiologic curve of the Chinese outbreak.
The fatal cases were primarily elderly patients, in particular those
aged ≥ 80 years (about 15%),
and 70 to 79 years (8.0%).
Approximately half (49.0%) of the critical patients with pre-existing comorbidities such as
oncological diseases, died.
While 1% of patients were aged 9 years or younger, no fatal cases occurred in this group.
WHO guidelines define three categories for disease severity based on clinical manifestations, from the Chinese CDC study.
Mild or Non Severe [ 81%]:
non-pneumonia and mild pneumonia
respiratory rate ≥ 30/min,
blood O2 saturation (SpO2) ≤ 93%,
PaO2/FiO2 ratio and/or lung infiltrates > 50% in 24 to 48 hrs;
septic shock, and/or
multiple organ dysfunction (MOD) or failure (MOF) 
It is estimated that 80% of patients are ASx or with very mild symptoms, while in the remaining 20% there is a respiratory syndrome with high fever, cough until severe respiratory failure is reached who may require ICU admission.
Among those who develop symptoms,
80% recover from the disease without needing hospital
15% become seriously ill and require oxygen
5% become critically ill and need intensive care.
In rare situations, children can develop a severe inflammatory syndrome a few weeks after infection. [WHO]
Characteristics of Severe disease include
Systemic complications such as sepsis, and septic shock.
The clinical course of the disease seems to predict a favourable trend in the majority of patients. In a percentage of cases still to be defined , after about a week there is a sudden worsening of clinical conditions with rapidly worsening respiratory failure and MOD/MOF.
normal or decreased total WBC and lymphocyte
Increased liver enzymes, LDH, muscle enzymes, CRP
For suspected cases, rapid antigen detection, and other investigations should be adopted for evaluating common respiratory pathogens and non-infectious conditions.
The Mayo Clinic proposed a COVID-19 self-assessment tool designed for establishing a potential candidate for a COVID-19 diagnostic test (https://www.mayoclinic.org/covid-19-self-assessment-tool).
Standard CXR has a low sensitivity in identifying early lung changes and in the initial stages of the disease.
In the more advanced stages of infection, the CXR generally shows bilateral multifocal alveolar opacities, which tend to confluence up to the complete opacity of the lung. Pleural effusion can be associated.
Given the high sensitivity of the method, chest computed tomography (CT), in particular high-resolution CT (HRCT), is the method of choice in the study of COVID-19 pneumonia, even in the initial stages.
The most common findings are multifocal bilateral "ground or ground glass" (GG) areas associated with consolidation areas with patchy distribution, mainly peripheral/subpleural and with greater involvement of the posterior regions and lower lobes. The "crazy paving" pattern can be also observed.
US can allow evaluating the evolution of the disease, from a focal interstitial pattern up to "white lung", with evidence of subpleural consolidations. It should be performed within the first 24 hours in the suspect and every 24/48 hours and can be useful for patient follow-up, choice of the setting of mechanical ventilation, and for the indication of prone positioning.
The main sonographic features are:
Pleural lines often thickened, irregular;
subpleural lesions, patchy consolidation or nodules.
B lines. can flow up to the square of "White lung".
air bronchogram within the consolidation
Perilesional pleural effusion