Lasser Fever Flashcards
(30 cards)
What’s Lassa fever?
What’s the causative agent of Lassa?
Lassa fever is an acute febrile illness caused by a single stranded enveloped RNA virus belonging to the virus family Arenaviridae.
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Causative Agent:
Lassa virus – a single-stranded, enveloped RNA virus in the Arenaviridae family. -
Disease Type:
One of the viral hemorrhagic fevers (VHFs).
What are the mode of transmission of Lassa?
-
Transmission:
Primarily zoonotic – humans acquire infection through contact with urine or feces of infected rodents (Mastomys natalensis, the “multimammate rat”).
Human-to-human transmission can also occur, especially in healthcare settings.
What’s the Historical Background
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First Identified:
In 1969, by Dr. Jordi Casals-Ariet and colleagues at Yale University. -
Origin of Isolation:
Isolated from American missionary nurses working in Lassa village, Borno State, Nigeria.
Two nurses died, one was evacuated and survived, and a lab technician later died.
Dr. Casals became severely ill but recovered.
When is Lassa fever most common?
And where
Epidemiology
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Seasonality:
Occurs year-round, but dry season (November to May) sees higher case numbers. -
Endemic Areas:
Nigeria, Guinea, Liberia, Sierra Leone, and parts of Senegal, Mali, CAR, DRC. -
Annual Impact:
Estimated 100,000–300,000 infections, with \~5,000 deaths annually in West Africa. -
Demographics:
Affects all ages, sexes, and races.
2025 Nigeria Situation Report (as of March 30)
- Suspected Cases: 3,779
- Confirmed Cases: 659
- Deaths: 122
- States Affected: 18
- Most Affected States: Bauchi, Edo, Ondo
What are the ways lassa can be transmitted?
Primary Transmission
- Direct contact with:
- Urine, feces, saliva, or blood of infected Mastomys rats.
- Ingestion of:
- Food or drinks contaminated with infected rodent excreta or secretions.
- Fomites:
- Contact with household items, surfaces, or utensils contaminated by infected rodents.
Secondary Transmission (Human-to-Human)
- Direct:
Close contact with infected patients or their body fluids (blood, urine, vomitus, saliva).
- Indirect:
Contact with contaminated objects like linens, gloves, or instruments.
- Possible Routes (still under investigation):
- Aerosol spread: Unclear, but suspected in some hospital outbreaks.
- Sexual transmission: Virus has been isolated from semen; possibility exists.
What are the Risk Factors
And people at high risk?
- Environmental and Lifestyle:
- Poor sanitation
- Bush burning (displaces rats into homes)
- Poor housing (allows rodent entry)
- Inadequate food storage
- Rodent hunting or consumption
- Cultural practices (e.g., touching corpses without protection)
People at Higher Risk
- Community level:
- Caregivers of Lassa patients
- Family members in close contact
- Healthcare setting:
- Doctors, nurses, lab staff, mortuary attendants
Specific High-Risk Situations:
- Handling patients without standard precautions
- Cleaning contaminated areas without protective gear
- Handling blood samples without biosafety
- Preparing corpses without PPE or infection control
What’s the incubation period of ladss
What are the clinical features of lassa fever? Even severe
Incubation Period
- Range: 3–24 days
Clinical Features
General Course:
- Gradual onset
- 80% of infections are asymptomatic or mild
Early Symptoms:
- Fever
- Malaise, weakness
- Headache, sore throat
- Muscle and chest pain
- Nausea, vomiting, diarrhea
- Abdominal pain, cough
Severe Symptoms:
- Facial swelling
- Pleural effusion
- Bleeding (gums, nose, GIT, vagina, injection sites)
- Hypotension and shock
- Proteinuria, hematuria
- CNS signs: Seizures, tremor, confusion, coma
Fatal Cases:
- Death occurs within 14 days from onset
Lassa Fever in Pregnancy the severity is higher in what trimester?
And% of death cases
- High severity in 3rd trimester
- Maternal and/or fetal death in over 80% of cases
What are the Suspicion Clues in Diagnosis
Suspicion Clues in Diagnosis
- Persistent high fever, pharyngitis, and retrosternal pain suggest Lassa Fever in \~70% of cases
Laboratory Diagnosis what type of specimen can be used
What are the Test Modalities: that are done?
Specimens:
- Blood (preferred)
- Urine
- Saliva
- CSF
- Others: Pleural/pericardial fluid, semen, breast milk
Test Modalities:
- ELISA (antigen detection)
- Indirect IF (IgG, IgM) – Gold standard
- RT-PCR – Highly recommended
- Virus culture – Only in BSL-4 labs
What are the Differential Diagnosis of lassa fever?
- Malaria
- Typhoid
- Bacterial sepsis
- Influenza
- Yellow fever
- Measles
- Shigellosis
- Meningococcemia
- Other VHFs: Ebola, Dengue
What are the Case Definition for Lassa Fever
Case Definition for Lassa Fever
Suspect Lassa Fever if:
Fever ≥ 38°C for at least 2 days AND any of the following:
- Negative malaria test
- One or more of:
- Chest pain
- Sore throat
- Headache
- Muscle pain
- Vomiting
- Diarrhea
OR
Fever with bleeding (e.g. gums, nose, GIT) or facial swelling
OR
Fever unresponsive to antimalarials or antibiotics after 48 hours
OR
Fever with recent contact (within 3 weeks) with a confirmed Lassa fever case
What’s the Treatment of Lassa Fever
Antiviral (Specific Therapy)
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Ribavirin
- Best if started within first 6 days
- Reduces case fatality from 55% to 5%
Supportive Care
- Fluid and electrolyte balance
- Hemodynamic monitoring
- Blood transfusion or blood products as needed
- Oxygen therapy or mechanical ventilation if respiratory distress occurs
- Dialysis in renal failure
- Antibiotics if secondary sepsis suspected
- Steroids (controversial, may help in severe inflammation)
What’s Infection Prevention and Control (IPC)?
Definition:
A set of policies, guidelines, and practices in healthcare settings to prevent the spread of pathogens among patients, staff, and visitors.
What are the Main Components of IPC and what does it entail
- Standard Precautions
- Minimum level of precautions for all patients, regardless of infection status.
- Aimed at reducing risk from:
- Blood
- Body fluids
- Secretions/excretions
- Non-intact skin
- Mucous membranes
Key Principle:
Treat every patient as potentially infectious.
- Transmission-Based Precautions/ Additional precautions
- Additional precautions when standard precautions are not sufficient.
- Tailored to the pathogen’s mode of transmission:
- Contact (e.g. MRSA, C. difficile)
- Droplet (e.g. influenza, COVID-19)
- Airborne (e.g. TB, measles, varicella)
What are the Golden Rule of Standard Precaution and it’s components
- Assume all patients may be infectious
- Apply standard precautions to every patient
- Protect yourself, the patient, and the environment
Components of Standard Precautions
- Hand hygiene – before/after contact, after gloves, before procedures
- Personal Protective Equipment (PPE) – gloves, gowns, masks, goggles
- Injection & sharp safety – safe handling/disposal of needles and sharps
- Cleaning, disinfection & sterilization – of equipment and surfaces
- Environmental cleaning & waste management
- Respiratory hygiene & cough etiquette
- Patient placement – isolate or cohort infectious patients when necessary
Hand hygiene
One of the most effective methods of prevent transmission of pathogen associated with health care
PPE
Specialized clothing or equipment worn by HCW for protection against pathogen.
Provides barrier to protect eyes, nose, mouth skin and clothing from contact with a patient body fluid.
Wear PPE appropriate to the activities being done.
PPE for transmission based precaution
Extra PPE is worn when there is a particular infection on how a pathogen can spread
Infection can spread through
Contact – touch eg lassa virus, Vibrio cholerae
Droplets – covid- 19, TB
Aerosol- air borne eg TB, measles,
Examples of PPE
Risk assessment for PPE selection
Depend on the risk and extent of contact anticipation with blood, body fluids , open skin, respiratory droplets, secretion etc
Select which PPE items to wear based on this assessment
Should be done for each patient each time
Make this routine
Gloves
Worn to:
Protective barrier to prevent gross contamination of the hands
To reduce the likelihood that microorganism present in hand will be transmitted to patient during care
Waste management color coding
Hand Hygiene
- Most effective method to prevent transmission of healthcare-associated infections.
- And Must be done? :
- Before and after patient contact
- Before aseptic procedures
- After body fluid exposure
- After contact with patient surroundings
What’s Personal Protective Equipment (PPE)?
Definition
- Specialized gear worn by healthcare workers to protect against pathogens.
- Forms a barrier for eyes, nose, mouth, skin, and clothing.
PPE Use
- Chosen based on activity and anticipated exposure.
- Should be worn appropriately and disposed of properly.
Types of Transmission and PPE Required with e.g
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Contact (e.g. Lassa, Cholera):
- Gloves, gowns
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Droplet (e.g. COVID-19, TB):
- Surgical mask, face shield/goggles
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Airborne (e.g. Measles, TB):
- N95 respirator, full PPE if high-risk
PPE Selection – Risk Assessment
- Evaluate every patient, every time.
- Consider contact with:
- Blood/body fluids
- Open wounds
- Respiratory droplets or secretions
- Base PPE choice on level and type of exposure anticipated.
Gloves
- Barrier protection against contamination
- Reduces transmission from HCW hands to patients
What are the Waste Management – Color Coding
- Infectious waste should be segregated using color-coded bins:
- Red – infectious waste
- Yellow – pathological waste
- Black – general (non-infectious) waste
