Emerging & Re-emerging Infectious Diseases Quiz

Study Notes

Emerging infections are newly appeared or rapidly increasing in incidence or geographic range.
Re-emerging infections are the reappearance of previously known infections after a period of decline.
Factors affecting emerging infections:
- Host factors: Human behavior, susceptibility to infection, international travel & commerce.
- Pathogen factors: High mutation frequency, co-evolution and pathogenicity, drug resistance development.
- Environmental factors: Climate change, ecosystems, technology and industry.

Avian influenza typically refers to influenza A virus.
The most well-known HPAI (highly pathogenic avian influenza) strain is H5N1.
Human infections first reported in 1997 in Hong Kong.
Over 700 human cases reported to WHO since 2003.
Transmission: Direct or indirect contact with infected poultry, contaminated environments.
- Human-to-human transmission occurs ONLY with mutations.
Symptoms: Incubation period 3-7 days, high fever, cough, sore throat, runny/blocked nose, fatigue, muscle/joint pain, diarrhea, vomiting, abdominal pain, chest pain, bleeding from nose and gum.
Complications: Hypoxemia, pneumonia, acute respiratory distress, respiratory failure, multiple organ dysfunction, secondary bacterial and fungal infections.

Caused by H1N1 influenza virus that infects pigs.
H1N1 is one of several influenza virus strains that cause seasonal flu in humans.
Transmission: Direct droplet transmission from cough/sneeze, indirectly through contaminated surfaces, improper handling/cooking of pork products.
Symptoms: Same as seasonal flu.
Complications: Same as seasonal flu.
Diagnosis: Nasopharyngeal aspirate/wash, oropharyngeal/throat swab.
- Viral culture, reverse transcription polymerase chain reaction (RT-PCR), rapid influenza diagnostic tests (RIDTs).
Treatment: Hospitalization and isolation, general and supportive treatment, oseltamivir (Tamiflu).

Viral respiratory illness caused by SARS-associated coronavirus (SARS-CoV-1).
Caused the 2002-2004 SARS outbreak.
No cases of SARS-CoV-1 have been reported worldwide since 2004.
Transmission: Direct droplet transmission from cough/sneeze, indirectly through contaminated surfaces.
Symptoms: Fever, chills, fatigue, headache, sore throat, muscle pain, diarrhea, dry cough, pneumonia, dyspnea, hypoxia.
Complications: Pneumonia, dyspnea, hypoxia, secondary bacterial infections, multi-organ failure.
Diagnosis: CT chest, ELISA, immunofluorescence, PCR.
Treatment: Hospital admission, isolation, supportive treatment, ventilator, antibiotics, steroids.

Viral respiratory infection caused by Middle East respiratory syndrome coronavirus (MERS-CoV).
First case identified in June 2012 in Jeddah, Saudi Arabia.
Larger outbreaks occurred in South Korea (2015) and Saudi Arabia (2018).
Transmission: Humans are typically infected from camels, either through direct contact or indirectly.
- Human-to-human spread requires close contact (healthcare or household).
Symptoms: Range from asymptomatic disease to severe pneumonia leading to ARDS.
- Complications: kidney failure, DIC, pericarditis.
Diagnosis: RT-PCR testing of blood and respiratory samples, ↓ white blood cell count, especially ↓ lymphocytes.
Treatment and Prevention: Same as SARS.

Zika virus is a member of the flaviviridae family.
Transmission: Spread by Aedes aegypti mosquitoes, sexual contact, blood transfusion, vertical (mother-to-child) transmission.
Occurred sporadically from Africa to Asia since the 1950s.
Spread eastward, across the Pacific Ocean to the Americas, leading to the 2015-2016 Zika virus epidemic.
Signs and Symptoms: Incubation period 3-14 days, typically asymptomatic, mild symptoms lasting 2-7 days (low fever, maculopapular rash, conjunctivitis, muscle and joint pain, malaise, headache).
Complications:
- Infection during pregnancy: pregnancy complications, microcephaly, congenital abnormalities in developing fetus and newborn.
- Guillain-Barré syndrome, neuropathy, myelitis.
Diagnosis: Molecular testing for presence of the virus (RT-PCR, immunoassay, virus isolation), serological testing for antibodies (ELISA).
Treatment: No specific treatment, fluids to prevent dehydration, paracetamol for joint pain and fever.