An overview of Viral hemorrhagic Fever with details and a special interest in Lassa Fever.

1. VIRAL HAEMORRHAGIC FEVERS
WITH SPECIAL INTEREST IN
LASSA FEVER
SEMINAR PRESENTATION
DEPARTMENT OF MEDICAL MICROBIOLOGY
ATBUTH, BAUCHI
DR. S. HARIS

2. Outline
• Overview of Viral Hemorrhagic Fevers (VHFs)
• Brief History of Lassa fever
• Epidemiology of Lassa fever
• Mode of Transmission
• Pathogenesis
• Clinical Features
• Diagnosis and Treatment
• Prevention and control
2

3. Overview 1/2
• Definition
 VHF is a term used to describe a severe multisystem febrile
syndrome sometimes associated with bleeding and caused by 4
distinct viral families:
– Arenaviridae
– Filoviridae
– Bunyaviridae
– Flaviviridae
3

4. Overview 2/2
• They are all caused by enveloped RNA viruses
• Almost wholly zoonotic in origin
• Often require a vector
• Geographically restricted to presence of host species
• Humans are accidental hosts
• Epidemics are sporadic, irregular
• With a few exceptions, no specific cure or vaccines
4

5. Arenaviridae
Groups Species Geographic distribution Clinical
syndrome
Mammalian reservoir
New
world
Lymphocytic chorionic
meningitis virus (LCMV)
Europe, Americas LCM Mus musculus
(Wild house mouse)
Junin virus (JUNV) Argentine pampas Argentine HF Calomys musculinus
Machupo virus (MACV) Beni region of Bolivia Bolivian HF Calomys callosus
Guanarito virus (GTOV) Venezuela Venezuelan HF Sigmodon alstoni,
Zygodontomys brevicauda
Sabia virus (SABV) Brazil Brazilian HF unknown
Whitewater Arroyo virus
(WWAV)
New Mexico, California HF Neotoma albigula (wood
rat)
Old
world
Lassa virus West Africa Lassa fever Mastomys natalensis
Lujo virus Zambia, S/Africa 5

6. Bunyaviridae
Genus Species Clinical syndrome Arthropod
vector
Mammalian
reservoir
Orthobunyavirus Ilesha virus HF Mosquitoes
Garissa virus HF
Phlebovirus RVF virus Rift valley fever Aedes Cattle, sheep
Nairovirus Crimean-Congo HF
virus
Crimean-Congo HF Ticks e.g.
Hyalomma spp
Cattle, sheep,
goats
Hantavirus Hantaan virus HF with renal syndrome,
hantavirus pulmonary
syndrome
Deer mouse,
other rodents
6

7. Filoviridae
Genus Species Geographical
distribution
Clinical
syndrome
Mammalian
reservoir
Marburgvirus Lake Victoria marburgvirus Uganda, Kenya,
SA,DRC.
Marburg virus
disease
Pterodidae
fruit bats
Ebolavirus Zaire ebolavirus (EBOV) DRC Ebola virus
disease
Pterodidae
fruit bats
Sudan ebolavirus (SUDV) Sudan
Bundibugyo ebolavirus
(BDBV)
Uganda
Reston ebolavirus (RESTV) Philippines, China
Taï Forest ebolavirus (TAFV) Cote d’Ivoire
7

8. Flaviviridae
Species Geographic
distribution
Clinical syndrome Arthropod vector
Dengue virus Worldwide, esp
tropical regions
Dengue, Dengue HF Aedes spp
Yellow fever virus Africa, South America Yellow fever Aedes aegypti
8

9. AFRICAN VHFs AT A GLANCE
VIRUS NATURAL
DISTRIBUTI
ON
RESERVI
OR
TRANSMIS
-SION
INCUBATI
ON
DISEASE HISTORY
Lassa West Africa Mastomys
Natalensis
Contact,
Formites,
Aerosol
6-21 days Lassa
Fever
First
isolated in
1969
CCHF Africa,
Central Asia,
Eastern
Europe,
Middle East
Tick:
Hyalomma
marginatm
and others.
Tick bite,
Contact,
Aerosol
3-12 days CCHF Isolated in
1969.
Mortality
6-76%
Rift
Valley
Fever
Africa,
Yemen, Saudi
Arabia
Mosquito:
Culicidae
Mosquito
bite,
Contact,
Aerosol
2-6 days Rift
Valley
Fever
Isolated
1931.
Mortality
2-6%
Ebola Africa Unknown
? Fruit bat
Contact,
?Aerosol
2-21 days Ebola HF Isolated
1976.
Mortality
60-90%

10. AFRICAN VHFs cont’d
VIRUS NATURAL
DISTRIBUTI
0N
RESERVI
OR
TRANSMI
S-SION
INCUBATI
ON
DISEASE HISTORY
Marbur
g
Africa Unknown Contact 2-14 days Marburg
HF
Isolated in
1967.
Mortality
23-90%
Dengue Africa, Asia,
Pacific
Americas
Mosquito:
Aedes
Mosquito
bite
Unknown Dengue
HF
Isolated in
1940.
Mortality
0-5%
Yellow
Fever
Tropical
Africa,
Americas
Mosquito:
Aedes
Mosquito
bite
3-6 days Yellow
Fever
Isolated
1927.
Mortality
22%

11. LASSA FEVER
• Lassa fever is an acute viral zoonotic illness caused by Lassa virus, an
arenavirus known to be responsible for a severe haemorrhagic fever
characterised by fever, muscle aches, sore throat, nausea, vomiting,
chest pain, abdominal pain e.t.c.
• First recognized in 1969 in an outbreak involving three missionary
nurses in Nigeria.
11

12. HISTORICAL REVIEW
• First identified in 1969 by Dr Jordi Casals Ariet and his team in Yale
University USA.
• In 1972, the rodent host of Lassa virus was classified as Mastomys
natalensis.
• Isolated from the blood of 3 American missionary nurses at a local
hospital in Lassa village, Borno state, Northern Nigeria.
• 2 nurses died, 1 flown to USA survived, 1 laboratory technician died,
Dr Casal fell severely ill but survived.
12

13. Lassa_epidemiology
 Endemic in West Africa: Nigeria and the
Mano Union countries – Liberia, Guinea,
Sierra Leone
 Serologic evidence of circulation in Mali,
Ghana, Cote d’Ivoire, Congo
 Exported to Europe and North America
 Seasonal pattern of outbreaks in the dry
months
 Tendency for nosocomial amplification
13

14. Lassa_epidemiology
• 300,000 to 500,000 cases and 5000 deaths occur yearly
across West Africa.
• Responsible for 10% to 15% of adult febrile admissions
to some West African hospitals, and about 40% of
nonsurgical deaths
• Lassa virus antibodies were detected in 21.3% of serum
samples from Nigeria.
• Antibodies to the virus: 8-22% in Sierra Leone, 4-55%
in Guinea.
14

15. Lassa fever_epidemiology
• Most infections (74-91%) are asymptomatic
• Case fatality rate
 1-2% overall
 20% in hospitalized patients
 50% during epidemics
 90% in third trimester pregnancy
15

16. CHRONOLOGY OF LF EPIDEMICS IN NIGERIA
• Jos 1969-1970
• Zonkwa in North Central, Onitsha in eastern Nigeria in 1974
• Pankshin in 1976.
• 1989 Ekpoma,Aboh Mbaise, and Aba
• 1989 till date – Ekpoma
• Lafia, from December 1993 to February 1994
• Northern part of Edo State, including Ekpoma, Igarra, and Ibilo, in
2001 and 2004
16

17. Summary of Clinical Cases Since 2001 at ISTH
Irrua, Edo State
1/2
YEAR NO OF
CONFIRMED
CASES
NO OF DEATHS CASE FATALITY
RATES (%)
2001 18 16 84.2
2002 23 12 52.2
2003 54 24 44.4
2004 63 19 30.3
2005 25 11 44.0
17

18. Summary of Clinical Cases Since 2001 at ISTH
Irrua, Edo State
2/2
2008 56 32 57.1
2009 137 25 18.3
18
YEAR NO OF
CONFIRMED CASES
NO OF DEATHS CASE FATALITY RATE
(%)
2010 76 25 32.9
2011 95 32 34.0
2012 159 44 27.6
2013 140 23 16.4
2014 82 21 25.6
2015 57 20 35.1
2016……. 52 20 38.5

19. LASSA FEVER IN NIGERIA 2/4
19
Year Total Number of
Confirmed Cases
Deaths Case Fatality Rate
(%)
Total Number of
States with
Confirmed Cases
2017 308 92 28.6 19
2018 633 171 27 23
2019 833 244 20 27
2020 833 174 20.8 23
2021 510 102 20 17
2022 797 158 19.8 24

20. LASSA FEVER IN NIGERIA 3/4
20

21. LASSA FEVER IN NIGERIA 4/4
21

22. SEASONALITY
22
Mainly in the dry season

23. Lassa fever_ecology
• Ecology
 Mammalian reservoir:
multimammate rat, Mastomys
natalensis
 Mastomys is a peridomestic rat
with a long hairless tail
 Found in the savannah, dry
forests, shrub land etc
 Rat sheds millions of particles in
excreta
23

25. VIROLOGY OF LASSA VIRUS
• Pleomorphic particles 50-300 nm in diameter
• Lipid envelope
• 4 major polypeptides
• Genome
 Bisegmented single-stranded ambisense RNA
molecule
 Replicates in cytoplasm
 Lineages
25

26. VIRAL GENOME
26

27. Physicochemical properties
The virus is inactivated by:
• Low level disinfectants such as QAC, Phenols, chlorine based
products and iodophor formulations( 37 minutes )
• 3% Acetic acid for 15 minutes
• Ultaviolet radiation ( 1200-2000 W/CM2) for 20 minutes
• Heating up to 56°C
• Exposure to a PH of < 5.5 or 8.5

28. Lassa fever_transmission
• Rodent-to-human
 food and materials contaminated with excreta
 inhalation of aerosolized virus
 catching and preparing Mastomys for food
• Human-to-human
 direct contact with body fluids, tissues, & excreta
 sharps: needles, scalpels
 inhalation of aerosolized virus
28

29. LIFE CYCLE OF LASSA VIRUS
29

30. LIFE CYCLE OF LASSA VIRUS
30

31. PATHOGENESIS
• Pathogenesis of Lassa fever is still poorly understood
• The infectious dose for lassa virus appears to be low (1 to 10
organisms)
• Lassa virus enters through different routes oral, mucous membrane,
parenteral (accidental innoculation), ? Inhalation, ? sex.
• There is pantropism for virtually all organs due to the virus affinity for
alpha D receptor present in most tissues.
• VHF viruses attack monocytes, macrophages and dendritic cells,
present in all tissues of the body.
31

32. PATHOGENESIS
• Down regulation of the immune system such as decrease in IL-8, and
impaired B- cell response. Patient who died from lassa fever have
significantly lower titre of specific antibodies than those who survived
or do not show antibody response at all.
• Another hypothesis is the ability of virus to inhibit and resist IFNs.
• Unchecked multiplication of the virus in various tissues leads to multi
-organ damage, shock and death.
• There is necrosis and hemorrhage in most organs; however, hepatic
involvement often is particularly prominent.
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33. Lassa fever_clinical features 1/3
• Incubation period: 3-21 days
• Insidious onset of fever and malaise
• Myalgia, prostration
• 4-7th day
 Sore throat with exudative patches
 Headache, generalized body pain, conjunctivitis, nausea and vomiting
 Diarrhoea, productive cough, hypotension and anaemia, proteinuria
• Without intervention
 Facial oedema, convulsions, mucosal bleeding, confusion or disorientation
 Progress to coma, death in the 3rd week
33

34. Lassa fever_clinical features 2/3
34

35. Lassa fever_clinical features 3/3
• Pharyngitis is the most sensitive indicator of Lassa fever (70%
sensitivity), but is not very specific (60%)
• Bleeding and edema, late symptoms occurring only in a small fraction
of patients, are not sensitive(∼20%), but highly specific for Lassa fever
(∼90%).
• In children of all age groups “swollen baby syndrome.” is specific and
is characterized by widespread edema, abdominal distension, and
bleeding with case fatality rate of about 80%.
35

36. Lassa fever_complications
• 8th nerve deafness
 unilateral or bilateral
 seen in about a third of patients
 may resolve spontaneously though many recover with permanent hearing
impairment
• Others
 Pericarditis
 Orchitis
 Uveitis
 Transient alopecia
36

37. SOME DIFFERENTIAL DIAGNOSIS
Malaria Bacterial meningitis
Typhoid fever Arboviral infection
Strep Pharyngitis Leptospirosis
Bacterial sepsis Anicteric hepatitis
Bacterial or Viral conjunctivitis
37

38. Laboratory Diagnosis
• Blood (Recommended)
• Urine
• Saliva
• Cerebrospinal fluid
• Others - pleural fluid, Pericardial fluid, Semen, Breast milk.
38

39. LAB DIAGNOSIS OF VHFs

40. MODALITIES OF LABORATORY INVESTIGATIONS
• Serology-
ELISA (antigen detection)
Indirect Immunofluorescence technique using virus infected cells (Vero
cells) to detect IgG and IgM antibodies is the Gold Standard for
serological diagnosis of LF.
• Culture (for isolation of virus using vero monkey cells in reference
lab. BSL-4)
• Molecular Diagnosis (Reversed Transcription Polymerase Chain
Reaction – RT - PCR) – Recommended.
40

41. Lassa virus-Immunofluorescence
41

42. Ancillary Laboratory investigations
• Full Blood Count.
• Biochemistry ( LFT, E/U/Cr. Urinalysis)
• • Leukopaenia or leucocytosis
• Thrombocytopenia
• Elevated liver enzymes (AST, ALT)
• Anemia or hemoconcentration
• Proteinuria, hematuria, and oliguria
• Azotemia, reduced plasma protein, Increase LDH and Amylase
42

43. Laboratory Prognostic Indicators
• High viremia
• Serum AST level>150IU/L
43

44. Case Definitions
• Suspected case: any individual presenting with one or more of the
following: malaise, fever, headache, sore throat, with history of
contact with excreta or urine of rodents, or confirmed or suspected
case of lassa fever.
• Confirmed case: any suspected case with laboratory confirmation
(positive IgM antibody, PCR or virus isolation)
• Probable case: any suspected case (see definition above) who died or
absconded without collection of specimen for laboratory testing
• Contact: Anyone who has been exposed to an infected person, or to
an infected person’s secretions, excretions, or tissues within three
weeks of last contact with a confirmed or probable case of Lassa fever
44

45. Treatment
• Ribavirin is the only drug with some therapeutic efficacy if initiated
early within 6 days of illness.
• SpecificTherapy. Case fatality can be reduced significantly as much as
55%- 5%.
• Experimental Treatment
• Use of neutralizing Lassa virus antibodies
Immunomodulators e.g Recombinant IL-1 receptor antagonist.
45

46. Supportive care
• Maintenance of fluid and electrolyte balance, with hemodynamic
monitoring as needed
• Blood/ blood product transfusion.
• Oxygen or mechanical ventilation, as indicated
• Dialysis, as indicated (25% of cases)
• Antibiotics if evidence of sepsis
• Steroids have not been shown to be of value
46

47. Prevention and Control
• No vaccine . Research underway.
• Rodent control
• Food protection
• High index of suspicion on all patients with febrile illness in endemic
areas
• Personal hygiene
• Health education/Community sensitization
47

48. References
• https://ncdc.gov.ng/diseases/sitreps/?cat=5&name=An update of
Lassa fever outbreak in Nigeria
• https://www.intechopen.com/chapters/62734
• https://www.researchgate.net/figure/Arenavirus-life-
cycle_fig1_318796802
• Jawetz, Melnick: Arthropod borne viruses, Medical Microbiology 24th
Edition
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