case study - hantavirus group 6 microbiology 401 fall 2007 chona herrella, saray felix, yanping fan

Case Study - Hantavirus

Group 6

Microbiology 401 Fall 2007

Chona Herrella, Saray Felix, Yanping Fan

Case Study

61 year old healthy male Patient resided in a house on four rural

acres Two months prior to hospitalization, he

cleaned a mouse nest from a wood pile Observed mice in the basement and

trapped two mice under the kitchen counters

Symptoms

Vermont resident hospitalized for: Three episodes of chills, fever, nausea, vomiting and anorexia

Patient had clear lungs and chest radiographs After admission in the hospital, patients health worsened:

Respiratory failure Profound Hypoxemia Hypotension – required mechanical ventilation Fluid in the lungs – Acute Respiratory Distress Syndrome (ARDS) Disseminated Intravascular Coagulation and Renal Insufficiency

Family Bunyaviridae

(-) ss RNA Enveloped 3 gene segments (L, M, S;

some S genes are ambisense, all other segments are (-) sense)

Three helical, spherical nucleocapsids

Segmented genomes of Hantavirus

Glycoprotein G2

Capsid

Glycoprotein G1

L Segment

3’ to 5’ terminal ends

M Segment

S Segment

Envelope

Family Bunyaviridae

All package their genomes together with the necessary Replicase

All have flexible nucleocapsids with helical symmetry. All have an envelope containing virally encoded

glycoprotein spikes that are involved in attachment and penetration.

All have genomes without a 5’ cap or a 3’ poly A tail Penetrates through cell-mediated endocytosis with

pH-dependent fusion

Sin nombre virus

Our case was caused by one of five genera, the Hantavirus also called the Sin nombre virus

Diagnosis

CBC (will show elevated white blood count) Platelet count (will be less than 150,000 and decreasing) X-ray of the chest (may show material invading the

lungs, involving both lungs) Liver enzymes (LDH will be elevated) Serum albumin (levels will be decreased) Hematocrit (will be increased, showing an increase in the

levels of red blood cells) Serological indirect testing for hantavirus

• serologic identification of IgM and IgG antibodies to SNV

• immunofluorescence assay

How does Sin Nombre virus cause Respiratory Distress?

HANTAVIRUS PULMONARY SYNDROME (HPS) Infection process:

The virus attacks host endothelial cells The immunological mechanism of host attacks the

infected endothelial cells causing permeability of pulmonary arteries and capillaries.

Studies have shown an increase amount of Cytokine-producing cells (TNF- , IL-2, and IFN-γ) and CD8+ T-cells in the lungs

Extravasation of fluids into the pleura cavity of the lungs

Results: shortness of breath

Radiologic Evolution of HPS

http://www.aafp.org/afp/20020915/1015.html

Cont’d

In severe cases the ff may occur: Myocardia depression resulting in Sinus Bradycardia - heart rate below 60 beats

per min with subsequent electromechanical dissociation - may not

have pulse ventricular tachycardia – increase in heart rate due to one

of the ventricles in the heart Fibrillation – contraction of the cardiac muscle of the

ventricles in the heart is uncoordinated. Which then fails to pump blood throughout the body causing unconsciousness within seconds and even death.

How can we get infected?

Urine

Feces

Saliva

Byproducts of mice that can infect humans through Aerolisation:

www.nsf.gov/news/mmg/mmg_disp.cfm?med_id=5854...

NOTE: One cannot be infected by another human!!!!

HPS Demographics

Vermont

Preventing Hantavirus Outbreak

Do not need to isolate patients infected with the virus! Why?It cannot be transmitted from person to

person, only through aerolisation of by-products of an infected mouse

Instead, one would need the demographics of the infected patients in order to…

Outbreak Prevention

Outbreak prevention cont’d

Need to locate mice population infected with the hantavirus

Need to remove or contain the population of infected mice

Need to inform the residents near the infected location where outbreak took place

Take preventive measures to assure that mice do not come into close contact with the residents through:

Preventive Measures:

Educating the population on how to decontaminate possible infected areas (cabins, garage, etc)

How to dispose of dead mice, waste materials and decontamination tools used (call local state health department)

Educate the population with the precautions needed to take in order to prevent infection

Precautions to be used:

Decontaminate infected (or possible infected) areas:

Wear protective gear Do not stir up rodent by-products (feces,

dried urine) Do not come in contact with rodents even if

they do not show signs of infection Do not invite rodents into your home

Other Hantavirus Diseases: Hemorrhagic Fever with Renal Syndrome (HFRS)

• A disease mainly found in Europe and Asia (Korea, China, East Russia and Balkans)

• Can also be transmitted through byproducts of mice carrying the disease (urine, feces and saliva)

• Initial symptoms:• flushing of the face, inflammation or redness of the eyes, or a rash.

• Later symptoms:• low blood pressure, acute shock, vascular leakage• malfunctioning of the kidneys and hemorrhaging (due to low platelet

counts)• Complete recovery can take weeks or months. • The severity of the disease varies depending upon the location of

the virus causing the infection…

Other Hantavirus Diseases cont’d:

Hantavirus causing Hemorrhagic Fever with Renal Syndrome (HFRS):Hantaan virusSeoul virusPuumala virusDobrava virus

Hantavirus Demographics