Lecture 11.2: Emerging and Re-emerging Infectious Disease Flashcards
National Institute of Allergy and Infectious Disease (NIAID) Classification (3)
- Group I – pathogens that have been newly recognised in the last 20 years
- Group II – Reemerging pathogens
- Group III – Agents with bioterrorism potential, subdivided
What is Ebola?
An infectious and frequently fatal disease marked by fever and severe internal bleeding, spread through contact with infected body fluids by a filovirus ( Ebola virus ), whose normal host species is unknown
How is Ebola Transmitted?
Human-to-human transmission occurs via skin and mucous membrane contact
with body fluids (rarely with a primate)
When is someone with Ebola infectious?
• Humans are not infectious until they develop symptoms
• Symptoms and signs persist in surviving patients for as long as it takes to
develop an effective immune response
Pathway of Ebola Infection
- Incubation period of 2 to 20 days
- Day 7-9, headache, myalgia, fever, fatigue
- Day 10, sudden high fever, vomiting blood, passive behaviour
- Day 11, bruising, brain damage, bleeding from nose, mouth, eyes, anus
- Day 12, loss of consciousness, seizures, massive internal bleeding, death
Can you recover from Ebola?
• During the 2nd week of symptoms, either defervescence occurs and patients
begin recovery, or patients develop fatal multiple organ failure and die
• Recovery is prolonged and may be complicated by recurrent hepatitis,
transverse myelitis, and orchitis
• The case fatality rate ranges from 25 to 90%
Can Ebola be a recurring infection?
• Ebola virus can persist in the central nervous system and ultimately cause a
relapse
• Ebola virus may persist in certain immune-privileged sites (eye, brain, testes)
• The virus may re-emerge from these sites and cause late sequelae or relapse • Sexual transmission from survivors to susceptible individuals is suspected
How many strains of Ebola are there?
- There are 5 strains of the Ebola Virus
* The deadliest is the Zaire Ebola strain
What are the chances of surviving Ebola?
- 8 out of 10 die
* So 2/10 chance of survival
What Group is Ebola classed in?
Group III
What is TB?
• Caused by a type of bacterium called Mycobacterium tuberculosis
• Mainly affects the lungs, but it can affect any part of the body, including the
abdomen, glands, bones and nervous system
What Group is TB classed in?
Group III
How many people have died of TB in the last 200 years?
• TB has claimed the lives of more than one billion people
• More deaths than from malaria, influenza, smallpox, HIV/AIDS, cholera, and
plague combined
• Although TB treatment exists, drug resistance is a continued threat
Microscopic Features of TB
- Rod-shaped bacillus
- Acid-fast stain
- Nonspore forming
- Produces mycolic acid
- Makes it difficult to Gram stain
- Protects the pathogen from antibiotic therapy and host defences
What are the 3 types of Tuberculosis?
- Primary Tuberculosis – initial case of tuberculosis disease
- Secondary Tuberculosis – reestablished tuberculosis
- Disseminated Tuberculosis – tuberculosis involving multiple systems
What are the 3 Stages of Tuberculosis Infection?
- Primary Infection (not transmissible)
- Latent Infection (not transmissible)
- Active Infection (transmissible)
How is TB Treated?
Today, four drugs are used to treat TB disease: • Isoniazid (1951) • Pyrazinamide (1952) • Ethambutol (1961) • Rifampin (1966)
This 4-drug cocktail is still the most common treatment for drug-susceptible TB
Mechanism of TB Infection
• M. tuberculosis cell wall interferes with macrophage function and immune cells
activation
• Inhibits the formation of the phagolysosome
• This allows Mt to escape into the cytoplasm
• Here it increases in number & eventually spreads to the lymph nodes
• From here it enters the blood and is distributed throughout the body
What are Tubercles?
Tubercles are aggregates of enlarged macrophages filled with bacteria
Is there a TB vaccine?
- Yes, the BCG Vaccination
- Often given to infants & small children in countries where TB is more common
- Protects against severe forms of TB in children
- The TB vaccine is not widely used
What is Measles?
- Paramyxovirus
- Single stranded RNA
- Enveloped virus (transmembrane hemagglutinin & glycoproteins)
- Airborne transmission
- Droplets expelled in coughing & sneezing
What Group is Measles in?
Group II
What are Signs and Symptoms of Measles?
- Highly contagious infection of the respiratory system
- Fever
- Malaise
- Cough
- Coryza & conjunctivitis
- Pathognomonic Koplik spots
What is the reason for most Measles related deaths? Examples?
• Most measles-related deaths are caused by complications associated with the disease • Blindness • Encephalitis • Severe Diarrhoea • Dehydration • Ear Infections • Severe Respiratory Infections (e.g. pneumonia)
Which group of people are most susceptible to Measles related deaths?
- Children below the age of 5
* Adults over the age of 50
Treatment for Measles (5)
- No specific antiviral treatment exists for measles virus
- Supportive care
- Good Nutrition
- Adequate Fluid Intake
- Treatment of Dehydration
What is Mumps?
• Mumps is an acute, generalised viral infection characterised by bilateral parotid
swelling
• Member of the family Paramyxoviridae, is an enveloped particle containing a
non-segmented negative strand RNA molecule of 15,384 nucleotides
What Group is Mumps in?
Group II
How is Mumps Transmitted?
MuV is transmitted via the respiratory route by inhalation or oral contact with infected respiratory droplets or secretions
Signs and Symptoms of Mumps (7)
• Flu-like Symptoms • Fever • Headache • Malaise • Myalgia • Anorexia • Parotitis (swelling of the parotid glands) then develops in 95% of symptomatic cases • Orchitis • Meningitis/Encephalitis
What is Monkeypox?
• Member of the Orthopoxvirus group
• Monkeypox virus is a species of double-stranded DNA virus which causes
monkeypox in humans and other animals
• Human disease occurs in Africa sporadically and in occasional epidemics
Why has there been an increase in incidence of Monkeypox?
A recent 20-fold increase in incidence is thought to be due to the cessation of
smallpox vaccination
Signs and Symptoms of Monkeypox
- Skin lesions occur
- Lymphadenopathy occurs in monkeypox but not in smallpox
- Secondary bacterial infection of the skin and lungs may occur
Treatment of Monkeypox
• The antiviral drugs have activity against monkeypox in vitro and in experimental
models.
• However, none of these drugs have been studied/used in endemic areas
• Past data from Africa suggests that the smallpox vaccine is at least 85%
effective in preventing monkeypox, because monkeypox virus is closely related
to the virus that causes smallpox
What is Bioterrorism?
The intentional release of viruses, bacteria, or other germs that can sicken or kill people, livestock, or crops
How can Bioterrorism be achieved/spread? (5)
- Aerosol Sprays
- Explosive Devices
- Food
- Water
- Absorbed or Injected into Skin
What are Category A Pathogens? What is their effect?
• Organisms/biological agents that pose the highest risk to national security and
public health
• Can be easily disseminated or transmitted from person to person
• Result in high mortality rates, have the potential for major public health impact
• Might cause public panic and social disruption
• Require special action for public health preparedness
What are Category B Pathogens? What is their effect?
• 2nd highest priority organisms/biological agents
• Are moderately easy to disseminate
• Result in moderate morbidity rates and low mortality rates
• Require specific enhancements for diagnostic capacity and enhanced disease
surveillance
What are Category C Pathogens? What is their effect?
• 3rd highest priority
Include emerging pathogens that could be engineered for mass dissemination in the future because of:
• Availability
• Ease of production and dissemination
• Potential for high morbidity and mortality rates and major health impact
What is Plague/Yersinia?
• Plague is caused by the bacteria Yersinia pestis
• A zoonotic bacteria usually found in small mammals and their fleas.
• People infected with Y. pestis often develop symptoms after an incubation
period of 1-7 days
What Group is Plague/Yersinia in?
Group III
`What are the 3 Types of Plague/Yersinia?
- Bubonic
- Pneumonic
- Septicemic
What form of Plague is the most common?
Bubonic
What is the incubation period of Bubonic Plague?
2-8 Days
Signs and Symptoms of Bubonic Plague (5)
- Fever
- Headache
- Chills
- Weakness
- One or more swollen, painful lymph nodes (called buboes)
What is the Vector for Bubonic Plague?
Fleas
What is the fatality rate for Bubonic Plague?
30-60%
What is the fatality rate for Pneumonia Plague?
100% if untreated
Treatment of Plague
Antibiotics
Signs and Symptoms of Septicemic Plague (7)
- Fever
- Chills
- Extreme Weakness
- Abdominal Pain
- Sock
- Possibly bleeding into the skin and other organs
- Skin & other tissues may turn black and die, especially on fingers, toes & nose
How is Septicemic Plague Spread?
- Septicemic plague can occur as the first symptom of plague
- May develop from untreated bubonic plague
- Result of bites of infected fleas or from handling an infected animal
What is incubation period of Pneumonic Plague?
1-3 Days
Signs and Symptoms of Pneumonic Plague (10)
- Fever
- Headache
- Weakness
- Rapidly developing pneumonia
- Shortness of Breath
- Chest Pain
- Cough
- Bloody or Watery Mucous
- Respiratory Failure
- Shock
How is Pneumonic Plague Spread?
• Pneumonic plague is the most serious form of the disease
• Only form of plague that can be spread from person to person (by infectious
droplets)
• May develop from untreated bubonic or septicemic plague after the bacteria
spread to the lungs
What is West Nile Virus?
- Neurotropic
- Arthropod-borne Flavivirus
- Single-stranded positive-sense RNA genome
- Causes West Nile Fever
- Only severe in 1% cases
What Group is West Nile Virus?
Group II
How is West Nile Virus Spread?
• Maintained in Enzootic cycle between mosquitoes and birds
• Can also infect and cause disease in horses and humans, which serve as
incidental dead-end hosts
Where is West Nile Virus Endemic?
Africa, Europe, the Middle East, and Asia
Signs and Symptoms of West Nile Virus (9)
• Most (4 out of 5) patients with West Nile virus infection have no symptoms.
• Fever
• Headache
• Body Aches
• Joint Pain
• Vomiting
• Diarrhoea
• Rash
• About 1 in 150 patients develop severe central nervous system involvement
with encephalitis, meningitis, or flaccid paralysis
What is Nipah Virus? (3)
- Nipah virus, scientific name Nipah henipavirus
- Bat-borne virus that causes Nipah virus infection in humans and other animals
- Has a high mortality rate
What Group is Nipah Virus in?
Group III
How does Nipah Virus present clinically?
- Asymptomatic Infection (subclinical)
- Acute Respiratory Infection
- Fatal Encephalitis
What is the fatality rate of Nipah Virus?
40% to 75%
How is Nipah Virus Spread? What is the Natural Host?
- Humans from animals (such as bats or pigs)
- Contaminated foods
- Directly human-to-human.
- Fruit bats of the Pteropodidae family are the natural host of Nipah virus
What treatment is available for the Nipah Virus?
- There is no treatment or vaccine available for either people or animals
- The primary treatment for humans is supportive care
