INFECTIOUS DISEASES
(ESP. COVID)
Presented by: Chukwukadibia Odunukwe
Definition
Epidemiology
Investigations/Studies
Differential diagnosis
Management
 Infectious diseases are disorders caused by organisms —
such as bacteria, viruses, fungi or parasites.
 The top 4 categories of infectious diseases—upper
respiratory tract infections, otitis media and otitis
externa, lower respiratory tract infections, and skin
infections.
 There are so many diseases caused by microbes. In this
presentation we are focusing on the Coronavirus and its
infection, COVID-19.
Incidence
Risk factors
Etiology/Pathogenesis
Transmission
Incidence
• United States cases
• worldwide cases
Risk factors
• close contact with suspected or confirmed cases of COVID-19
• residence or travel to areas with high incidence of COVID-19
Etiology
• Incubation: enters cells via the angiotensin-converting enzyme 2
receptors, especially on epithelium that line the respiratory tract.
• TMPRSS2 primes spike protein on SARS-CoV-2 for entry
• The incubation period is thought to be 2-14 days post-exposure
https://www.frontiersin.org/articles/10.3389/fimmu.2020.576745/full
 ACE2 is mainly expressed on type II alveolar epithelial
cells, but weakly expressed on the surface of epithelial cells
in the oral and nasal mucosa and nasopharynx.
 Moreover, ACE2 is highly expressed on myocardial cells,
proximal tubule cells of the kidney, and bladder
urothelial cells, and is abundantly expressed on the
enterocytes of the small intestine, especially in the ileum.
 ACE2 downregulation and local immune response to the
virus is the main process behind multiorgan failure.
Illness severity of this infection ranges from mild to critical
Mild (~81% of cases):
• no dyspnea
Severe (~14%):
• dyspnea
• respiratory rate ≥ 30/min
• hypoxia
Critical (~5%):
• respiratory failure
• shock
• multiorgan dysfunction
http://ca.china-embassy.org/eng/zgxw/202003/t20200325_4633370.htm
https://ccforum.biomedcentral.com/articles/10.1186/s13054-020-03120-0
Transmission
1. Person-to-person transmission.
• usually via respiratory droplets.
• the virus can be disseminated into the air when the infected person coughs or
sneezes.
• can also be transmitted longer distances via airborne route.
• research suggests that droplets may get aerosolized and be carried > 6 ft (2 meters)
with speaking, coughing, or sneezing.
2. Fomite transmission
• touching an infected surface and subsequently touching one's eyes, nose, or
mouth can result in infection
• therefore, disinfectant is recommended.
3. Fecal-oral transmission
• the SARS-CoV-2 RNA has been detected in stool, so fecal-oral transmission is
possible.
IMAGING
Radiographs: CXR (often normal), CT.
Chest CT findings:
• ground-glass opacification (GGO)
• consolidative abnormalities may or may not be present
• more likely to affect both lungs, particularly in the lower
lobes, and in a peripheral distribution
https://pubs.rsna.org/doi/full/10.1148/rg.2020200159
Diagnostic tests
a. Reverse-transcription PCR (RT-PCR) for SARS-CoV-2
Method:
• nasopharyngeal swab
• sputum collection in patients with a productive cough
• positive test indicates detection of viral genome regions specific to
SARS-CoV-2
b. Antigen test
Method:
• nasal swab
• positive result indicates detection of SARS-CoV-2 antigens
Serum labs
• WBC count
• variable (leukopenia, leukocytosis, and lymphopenia)
• lymphopenia is more common
• lactate dehydrogenase and ferritin level are commonly elevated
• IL-6 may be elevated
 Influenza
 Common cold
 Community-acquired pneumonia
 Other viral or bacterial respiratory infections
 Aspiration pneumonia
 Pneumocystis jirovecii pneumonia
 Middle East respiratory syndrome (MERS)
 Avian influenza A (H7N9) virus infection
 Avian influenza A (H5N1) virus infection
 Pulmonary tuberculosis
 Febrile neutropenia
 Other.GATIONS
1. Supportive care and isolation
• for mild cases, patients are isolated to their homes and
symptomatically managed.
• adults with mild-to-moderate COVID-19 infection typically remain
infectious for up to ~10 days after symptom onset.
2. Hospitalization with potential oxygen supplementation or
mechanical ventilation
• for severe disease, characterized by hypoxia, an oxygen
requirement, or ventilatory support.
• hospitalized patients with severe disease but not yet on oxygen
supplementation.
3. Pharmacologic
• Still under research
Current medications:
• lopinavir-ritonavir (a combined protease inhibitor)
• Remdesivir (a novel nucleotide analog that impairs RNA-
dependent polymerases)
• IL-6 pathway inhibitors: tocilizumab, siltuximab, sarilumab
a. Remdesivir only
• hospitalized patients with severe disease who are
receiving supplemental oxygen (including high-flow
oxygen and non-invasive ventilation).
b. Low-dose dexamethasone AND remdesivir
• hospitalized patients with severe disease who require
mechanical ventilation (critically ill).
c. Low-dose dexamethasone only.
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