Lassa fever

A neglected disease in Africa

Who are the patients and what are their outcomes ?

A Dahmane, R Zachariah, R Van den Bergh, T Reid, Y Nzomukunda, M Allaouna ,P Alders ,M Van Herp ,R Souya, Dr

Grant, S Hinderaker, AD Harries

Medecins Sans Frontières Brussels – Luxembourg, Sierra Leone International Union against Tuberculosis and Lung disease, Paris, France

University of Bergen (Norway) ,London School of Hygiene and Tropical Medicine London, UK.

LASSA FEVER

• An acute and severe viral haemorrhagic illness

• Caused by the “Lassa virus”

• Infections /year - 300-500,000

• Deaths - 5000

• Seen in the Lassa fever belt (West Africa)

Côte d’Ivoire

Mali Guinea Bissau

Senegal

Guinea

Reservoir & Transmission (Mastomys Natalensis - Zoonotic disease)

Man to Man - Any body fluid (stool, urine, vomit, saliva,

sweat, mothers milk, blood, aerosol transmission)

Rat to Man - exposure to rat excreta, urine

or blood

Mother to child transmission

SIERRA LEONE

Gondama Referal Center

• 220 bed MSF referral hospital

• Pediatrics and emergency obstetric care

• 2011 : Increased number of Lassa cases in GRC

Operational challenges

Early diagnosis is difficult – Mimics malaria, and

other severe diseases

(No rapid diagnostic test for lassa)

High case fatality – 50%

Nosocomial transmission within MSF health

staff 2 nurses died, ( 2011)

Blood transfusions – perhaps a source of

transmission

MANAGEMENT OF SUSPECTED LASSA FEVER

PATIENTS

• GRC :Identification

and isolation of

suspected cases

• Kenema

hospital:Laboratory

testing and treatment

Lassa Fever - a neglected disease !!

• No preventive vaccine (unlike yellow fever)

• No accessible diagnostics

• Expensive life saving treatment: Ribavirin treatment (5400 Euros/ 1patient!!)

• Limited research – Class A select agent bioterrorism – American military

STUDY OBJECTIVES

In the MSF hospital in Bo Sierra-leone

• To describe the characteristics,

management & outcomes of children

and women with suspected or

confirmed Lassa fever

METHODS 1

Study Design: Retrospective audit of patients files

Period: August - December 2011

Site: Gondama referral hospital (GRC)

Study Population: Confirmed & suspected Lassa fever

Ethics MSF & Union

METHODS 2

WHO Case definition for Lassa fever

A patient with fever > 38 degrees Celsius

• Unresponsive to anti-malarial and broad spectrum antibiotics within 72 hours

• And at least two major or one major and two minor criteria

METHODS 3

MAJOR CRITERIA

• Abnormal bleeding

• Swollen neck or face

• Conjunctivitis or sub-conjunctival haemorrhage

• Spontaneous abortion

• Unexplained tinnitus or altered hearing during a febrile illness

• Persistent low systolic blood pressure

• Known exposure to a confirmed Lassa patient or readmitted within three weeks of inpatient care for illness with fever

• Markedly elevated SGOT/AST

MINOR CRITERIA

• Headache

• Sore throat

• Persistent vomiting

• Diffuse abdominal pain/tenderness

• Retro-sternal pain

• Diarrhoea

• Generalized myalgia and arthralgia

• Profuse weakness

• Proteinuria

• WBC count < 4000 L

Lassa fever “suspect” : Patient fits the case definition but laboratory

negative

Lassa fever confirmed: Patient with Lassa fever laboratory test positive

DELAY FOR RIBAVIRIN TREATMENT

( Ideal delay < 6 days )

Referred patients to GRC

Start anti-malarial and /or AB

Wait for 72 Hrs

Suspicion of Lassa Fever

Test in Kenema hospital

Results in 1-5 days

Start Ribavirin

Time in days

Health centers

RESULTS 1 Characteristics of the study population

Lassa confirmed

N= 36 (43%)

Lassa suspect

N= 48 (57%)

Total cases

N=84

MALE 19 (53%) 27 (56%) 46 (55%)

FEMALE 17 (47%) 21(44%) 38 (45%)

AGE

≤ 2 yrs 21 (58%) 29 (62%) 50 (60%)

> 2 – ≤ 5 yrs 4 (11%) 10 (21%) 14 (17%)

> 5 – ≤ 15 yrs 4 ( 11%) 4 (9%) 8 (10%)

> 15 yrs 7 (19%) 4 (9%) 11 (13%)

RESULTS 2

Case Fatality Rate

Lassa

Confirmed

N=36

Lassa

Suspect

N=48

Total

N = 84

Deaths

22 (61%)

21 (44%)

43 (51%)

RESULTS 4 MAJOR CRITERIA

MAJOR CRITERIA

0

10

20

30

40

50

60

blee

ding

swollen face

conjou

nctiv

itis

Spo

ntan

eous

abo

rtion

tinnitus

low B

P

expo

sure

to LF

read

mission

with

in 3 w

ks

SGOT/

ASAT high

coag

ulation test +

%

lassa lab + (n=36)

lassa suspect (n=48)

Stage 3

RESULTS 5

PRESENTATION - MINOR CRITERIA

MINOR CRITERIA

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

head

ache

sore th

roat

persistent vom

iting

abdo

minal pain

retro

-stern

al pain

diar

rohe

a

mya

lgia/ a

rthralgia

profus

e wea

knes

s

proteinu

ria

WBC <

400

0

%

lassa lab + (n=36)

lassa suspect (n=48)

RESULTS 6 WHO CASE DEFINITION – HOW USEFUL?

DID NOT MEET

WHO CASE DEFINITION

N=84

Lassa Confirmed

17/ 36 (47%)

Lassa Suspect

31/ 48 (65%)

RESULTS 7 TIME DELAY

Admission to Lassa Testing From admission to Testing

0

1

2

3

4

5

6

7

8

9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Days

nu

mb

er

of

pati

en

ts

Lassa confirmed

lassa suspect

Data available for 81 cases

Desired time to testing ?

RESULTS 8

TIME DELAY

ADMISSION TO RIBAVIRIN

Ribavirin treatment Admission

Deaths Alive

Mean (Days)

14

6

STUDY LIMITATIONS

• Preliminary data analysis

• Missing data in patient files

• No written reports from patients referred to Kenema referral hospital

CONCLUSIONS

• Very high case fatality rate

• Only 50 % of patients fit in the WHO case definition late diagnosis

• Urgent need for improving Lassa diagnostic strategy

• A neglected disease that should benefit from MSF advocacy

Acknowledgements

Many thanks to the patients, MSF staff working in Sierra Leone , cell 7 ,OCB referent and LUXOR team