Emerging and Re-emerging Infectious Diseases

Emerging Infectious Diseases

Diseases caused by newly discovered infectious agents that have appeared in the human population in the last two decades and are projected to increase

COVID-19

Give an example of the Emerging Infectious Diseases

Re-emerging Infectious Diseases

Previously controlled diseases that are once again significant public health threats, often spreading to new areas

Monkeypox

Give an example of Re-emerging Infectious Diseases?

Evolution of pathogens (e.g., drug resistance)
Improper antibiotic use (prescribing, patient adherence, counterfeit drugs)
Use of antimicrobials in animals and agriculture
Vector resistance to pesticides

What are the agent-related factors that contribute to emergence?

Immunosuppression
Unsafe sexual practices
Increased travel and migration
Changes in food production and behavior
Socioeconomic inequalities

What are the host-related factors?

Deforestation, urbanization, climate change
El Niño and natural disasters
Global warming (↑ Malaria, Dengue)
Weak surveillance systems
Cross-species transmission (zoonoses)

What are the environment-related factors?

Mycobacterium tuberculosis, an acid-fast, obligate aerobe with a lipid-rich (mycolic acid) cell wall.

What is the causative agent of TB?

Airborne transmission (e.g., coughing

What is the primary mode of TB transmission?

10-15

How many people can an active TB patient infect?

Pulmonary (86%): chronic cough >2 weeks, chest pain, hemoptysis
Systemic (14–20%): fever, night sweats, fatigue, weight loss

What are the pulmonary and systemic symptoms of TB?

Uses Ziehl-Neelsen (heating step) or Kinyoun stain (cold)
Less sensitive
Cannot differentiate MTB vs. NTMB
LED fluorescence microscopy is more sensitive than light microscopy

What are the key features of AFB smear microscopy?

Can differentiate MTB from NTMB
Can identify slow vs. fast growers

Why is culture the gold standard for TB?

Molecular test
Detects MTB and rifampicin resistance
Results in <2 hours
Sensitivity: 89%; Specificity: 99%

What is the role of GeneXpert MTB/RIF Assay?

For latent TB diagnosis
When smear/culture/GeneXpert is negative but suspicion remains
Costly and complex (e.g., Quantiferon, EliSpot)

When is IGRA (Interferon-Gamma Release Assay) used?

A positive-sense RNA virus from the Coronaviridae family; largest known RNA virus.

What type of virus is SARS-CoV-2?

Direct: respiratory droplets
Indirect: contaminated surfaces or hands (fomite transmission)

What are the transmission routes of SARS-CoV-2?

RT-PCR (detects viral RNA). Requires BSL-2 facility

What is the gold standard for COVID-19 diagnosis?

Cannot distinguish between active and past infection
Poor test of cure
False negatives from poor sampling

What are the limitations of RT-PCR?

Detect past infection (IgM, IgG)
Useful for serosurveys, clearance from quarantine, and plasma donation
Not reliable for early diagnosis

What is the role of antibody tests in COVID-19?

increased Transmissibility
Alters disease presentation
Reduces effectiveness of diagnostics/vaccines

What defines a variant of concern?

Causes community transmission or multiple COVID-19 cases/ clusters or has been detected in multiple countries

What defines a variant of interest?

Yes, due to broad immune response targeting multiple spike protein sites.

Will vaccines still work against variants?

Hand hygiene
Cough etiquette
Ventilation
Masking

What are basic COVID-19 protective measures?

Ebola

hemorrhagic fever; sporadic African outbreaks since 1976

Zika

associated with birth defects (microcephaly); outbreaks in Americas since 2015

PCR

how is zika diagnosed

Multidrug resistance (fluconazole: 93%; amphotericin B: 35%)
Difficult to identify with standard lab tests
Spreads in hospitals; high mortality (~60%)

What makes Candida auris an emerging threat?

MALDI-TOF MS (VITEK MS, Bruker Biotyper)
PCR
CHROMagar with color differentiation
LAMP and T2 MR (research)

How is C. auris diagnosed?

Contact precautions
Single room isolation
Daily disinfection with EPA-approved agents
Report to CDC and health departments

What infection control measures are recommended for C. auris?

Prevents selection pressure
Helps reduce overgrowth of drug-resistant fungi
Ensures appropriate use of antifungals

What is the importance of antimicrobial stewardship in C. auris?

Candida medium supplemented with Pal’s agar can be used

What is chromagar composed of?

White to cream colonies with a smooth edge

C. auris appearance on SDA

N-acetyl glucosamine, succinate, and gluconate

C. auris grows well at 38°C or 42°C and is assimilated with —