Introduction
The resurgence of diseases once thought to be eliminated, alongside the appearance of new pathogens, has emerged as a critical concern in global health. The reappearance of measles in 2025, despite its near-eradication, underscores the vulnerabilities in public health systems and the dynamic nature of infectious diseases. Emerging and reemerging infectious diseases (EIDs and RIDs) have underscored the need for constant vigilance, advanced surveillance, and integrated global health responses.
Factors Driving Emergence and Reemergence
Several interconnected factors contribute to the emergence or reemergence of infectious diseases:
- Urbanization and Overcrowding: Rapid population growth and under-planned urban expansion increase human contact with pathogens and strain public health resources.
- Environmental Degradation and Poor Sanitation: These create ideal conditions for vectors and facilitate the spread of diseases.
- Antibiotic Resistance: Unregulated use of antimicrobials has led to resistance, allowing previously controlled diseases to reappear in more virulent and harder-to-treat forms.
- Human Encroachment on Wildlife Habitats: Increased human-wildlife interaction elevates the risk of zoonotic spillovers, exemplified by viruses like Nipah and Hendra.
- International Travel and Globalization: These factors accelerate the transcontinental spread of infections, as seen with SARS, COVID-19, and Monkeypox.
- Microbial Mutation: Natural evolution and recombination in pathogens can create new strains with pandemic potential.
Emerging Infectious Diseases (EIDs)
EIDs are those that have increased in incidence or geographic spread in recent decades or pose a significant threat to do so. Over 30 new diseases have emerged in the past three decades, often with limited treatment and vaccination options. Key examples include:
- COVID-19: The most impactful pandemic in a century, revealing systemic weaknesses in health infrastructure.
- Human Monkeypox (2022): Spread across several countries, showcasing the global interconnectedness of infectious threats.
- Tomato Flu (2022): Emerged in Kerala and Tamil Nadu, India, representing localized but potentially expanding threats.
- Others: AIDS, Ebola, Hanta virus, novel E. coli strains, and SARS—all of which demonstrate the diverse origins and rapid emergence of novel pathogens.
Reemerging Infectious Diseases (RIDs)
Reemerging diseases are those once under control but now resurface due to factors like resistance and lapses in immunization. Notable examples include:
- Tuberculosis: Multi-drug resistant TB is a growing threat, complicating control measures.
- Malaria: Increasing drug resistance has led to resurgence in several regions.
- Nosocomial Infections: Particularly those caused by vancomycin-resistant Enterococci.
- Respiratory and Gastrointestinal Infections: Caused by resistant strains of Pneumococci, Hemophilus influenzae, and Shigella dysenteriae.
- Sexually Transmitted Diseases: Particularly those caused by Neisseria gonorrhoeae, now resistant to many antibiotics.
Distinguishing RIDs from Cyclical Trends
While some diseases like influenza and chickenpox follow predictable seasonal patterns, RIDs such as TB and dengue resurface after periods of apparent control, often unpredictably. This difference is crucial in designing surveillance and response strategies.
Surveillance and Early Detection
The identification of emerging diseases relies on multiple methodologies:
- Syndromic Surveillance
- Laboratory Diagnostics (PCR, ELISA, culture)
- Community-Based Reports
- Outbreak Investigations
- International Alerts from bodies like WHO and ICMR
- Genomic Surveillance to monitor mutations and evolution of pathogens
India’s Surveillance Framework
India has developed several robust mechanisms to detect and manage outbreaks:
- IDSP: Integrated Disease Surveillance Programme
- NCDC: National Centre for Disease Control
- ICMR-NIV: National Institute of Virology
- NHM: National Health Mission
- EIS Officers: Trained epidemiologists for field response
- Media Scanning and Verification Cell: Monitors for potential health alerts in real-time
Bioterrorism as an Emerging Risk
The threat of bioterrorism further complicates the landscape of infectious disease. The anthrax attacks of the early 2000s revealed how pathogens could be weaponized, highlighting the urgent need for dual-purpose preparedness—covering both natural outbreaks and deliberate releases.
Global Health Preparedness and the One Health Approach
Efforts such as the International Health Regulations (IHR) and the Global Health Security Agenda aim to improve global readiness. Increasingly, the One Health approach, which considers the interdependence of human, animal, and environmental health, is viewed as essential for preventing future pandemics.
Conclusion
Emerging and reemerging infectious diseases remain one of the greatest threats to global health. Their multifactorial causation demands integrated, interdisciplinary, and globally coordinated strategies. Surveillance, rapid response systems, antimicrobial stewardship, and One Health investments must be central to preparedness plans. As history and current events remind us, no nation is immune, and global solidarity is key to defeating these invisible threats.
MCQs
1. Which of the following is a key characteristic of emerging infectious diseases (EIDs)?
A. Diseases that have disappeared from human populations
B. Diseases confined to specific rural regions
C. Diseases whose incidence is increasing or likely to increase
D. Diseases only affecting animal populations
Correct Answer: C. Diseases whose incidence is increasing or likely to increase
2. Which of the following is NOT a factor responsible for the emergence of infectious diseases?
A. Microbial genetic mutation
B. Increased international travel
C. Strong public health infrastructure
D. Poor sanitation
Correct Answer: C. Strong public health infrastructure
3. All of the following are examples of emerging infectious diseases EXCEPT:
A. SARS
B. AIDS
C. Tuberculosis
D. Tomato flu
Correct Answer: C. Tuberculosis
4. Which of the following is a re-emerging disease due to antimicrobial resistance?
A. Ebola
B. Measles
C. Tuberculosis
D. Monkeypox
Correct Answer: C. Tuberculosis
5. What differentiates a cyclic trend from a re-emerging disease?
A. Cyclic trends are unpredictable; re-emerging diseases are predictable
B. Cyclic trends show natural seasonal variation; re-emerging diseases follow decline and resurgence
C. Cyclic trends only affect children
D. Re-emerging diseases occur only in rural areas
Correct Answer: B. Cyclic trends show natural seasonal variation; re-emerging diseases follow decline and resurgence
6. Which surveillance method is NOT used to identify emerging diseases?
A. Syndromic surveillance
B. Community-based reporting
C. Astrological forecasting
D. Genomic surveillance
Correct Answer: C. Astrological forecasting
7. What is the full form of IDSP in India’s disease control mechanism?
A. International Disease Screening Programme
B. Integrated Disease Surveillance Programme
C. Indian Disease Surveillance Portal
D. Infectious Disease Safety Plan
Correct Answer: B. Integrated Disease Surveillance Programme
8. Which of the following is NOT commonly associated with antimicrobial resistance?
A. Overuse of antibiotics
B. Microbial mutation
C. Adequate antibiotic stewardship
D. Incomplete treatment courses
Correct Answer: C. Adequate antibiotic stewardship
9. What is the role of the One Health approach in tackling EIDs and RIDs?
A. Focuses only on hospital infection control
B. Integrates human, animal, and environmental health
C. Bans all international travel
D. Promotes herbal remedies only
Correct Answer: B. Integrates human, animal, and environmental health
DoctorDP 