Emerging and Re-emerging Infections

Emerging Infections - Defining the Foe

• Emerging Infection: Incidence ↑ in new host/area or existing one.
• Re-emerging Infection: Previously ↓, now ↑ in incidence/range.

  ⭐ A disease re-emerging due to factors like waning vaccine immunity or antimicrobial resistance.

• Deliberately Emerging: Bioterrorism agents (e.g., Anthrax).
• Factors Driving Emergence:
  • Ecological changes (e.g., deforestation)
  • Demographics & human behavior (e.g., urbanization, sexual practices)
  • Microbial adaptation (e.g., antigenic drift/shift)
  • International travel & commerce
  • Breakdown in public health measures
• Key Indian Surveillance: Integrated Disease Surveillance Programme (IDSP).

Viral Villains - Airborne & Zoonotic

• Nipah Virus (NiV)
  • Reservoir: Pteropus fruit bats.

    ⭐ The natural reservoir of Nipah virus is the Pteropus fruit bat.

  • Transmission: Contaminated fruits/date palm sap; direct contact with infected bats, pigs; human-to-human.
  • Clinical: Encephalitis, respiratory distress; high mortality.
  • Diagnosis: RT-PCR (throat swab, CSF), ELISA (IgM, IgG).
  • Treatment: Supportive care; Ribavirin efficacy debated.
  • 📌 NIPAH: Neurological, In Pteropus bats, Affects Humans/Pigs.
• Influenza (H1N1, H5N1)
  • Orthomyxovirus; segmented RNA genome.
  • Antigenic Drift (minor changes, epidemics) vs. Shift (major changes, pandemics).
  • Clinical: Fever, cough, myalgia; severe respiratory illness (especially H5N1).
  • Diagnosis: RT-PCR (nasopharyngeal swab).
  • Treatment: Neuraminidase inhibitors (Oseltamivir 75mg BD for 5 days; Zanamivir).
• COVID-19 (SARS-CoV-2)
  • Key Variants of Concern (VoCs): e.g., Omicron. Monitor current dominant strains.
  • Long COVID: Persistent multi-system symptoms (neurocognitive, cardiac, pulmonary).
  • Prevention & Management: Vaccination (updated boosters), antivirals, masks, hygiene.

Vector Vanguard - Mosquitoes & Mites

• Dengue (Flavivirus, Aedes)
  • DENV1-4 serotypes
  • Warning signs: Abd. pain, persistent vomiting, fluid accumulation, mucosal bleed, lethargy, liver enlargement; Platelets < 100,000/mm³
  • DHF/DSS criteria; Tourniquet test (+)
• Chikungunya (Togavirus, Aedes)
  • High fever, severe debilitating arthralgia, rash
• Kyasanur Forest Disease (KFD) (Flavivirus, Haemaphysalis ticks)
  • 'Monkey Fever'; Monkeys amplify
  • Biphasic: Fever, HA, myalgia → hemorrhagic/neuro
  • 📌 KFD: Karnataka Forest Disease, Monkeys Die
• Scrub Typhus (Orientia tsutsugamushi, Trombiculid mites/chiggers)
  • Eschar at bite site (key!)
  • Fever, rash, lymphadenopathy
  • Weil-Felix: OX-K (+)

⭐ The presence of an eschar is highly suggestive of Scrub Typhus.

AMR Alert - Superbugs Strike Back

• Definitions:
  • AMR: Microorganism's resistance to a drug previously effective for treatment.
  • MDR (Multidrug-Resistant): Non-susceptibility to ≥1 agent in ≥3 antimicrobial categories.
  • XDR (Extensively Drug-Resistant): Non-susceptibility to ≥1 agent in all but ≤2 categories.
  • PDR (Pandrug-Resistant): Non-susceptibility to all agents in all antimicrobial categories.
• MDR-TB: Resistance to at least Isoniazid & Rifampicin. Diagnosis: CBNAAT, Line Probe Assay. Management: Programmatic Management of Drug-resistant TB (PMDT) principles.
• MRSA (Methicillin-Resistant Staphylococcus aureus): Hospital-acquired (HA-MRSA) vs. Community-acquired (CA-MRSA). Treatment: Vancomycin, Linezolid, Daptomycin.
• CRE (Carbapenem-Resistant Enterobacteriaceae): Key enzymes (e.g., NDM-1, KPC, OXA-48). Limited treatment: Colistin, Tigecycline.
• India's National Action Plan on AMR (NAP-AMR): Addresses AMR through key strategic priorities.

⭐ NDM-1 (New Delhi metallo-beta-lactamase-1) confers resistance to a broad range of beta-lactam antibiotics, including carbapenems, posing a significant treatment challenge globally and in India.

High‑Yield Points - ⚡ Biggest Takeaways

• Nipah virus: Fruit bat reservoir; causes encephalitis; human-to-human spread confirmed.
• Zika virus: Aedes vector; linked to congenital microcephaly and Guillain-Barré syndrome.
• KFD (Kyasanur Forest Disease): Tick-borne flavivirus in India (Karnataka); causes hemorrhagic fever.
• Scrub Typhus: O. tsutsugamushi via mite (chigger) bites; look for fever, rash, eschar.
• Avian Influenza (H5N1, H7N9): From infected poultry; severe respiratory illness, high mortality.
• Monkeypox (Mpox): Orthopoxvirus; close contact spread; characteristic vesicular rash and lymphadenopathy.