Lassa Fever and other Viral Hemorrhagic Fevers

• Lassa fever is a viral hemorrhagic disease
• Viral haemorrhagic fevers are diseases caused by four groups of viruses that manifest as febrile illnesses with ranging vascular deregulatory changes in the body.
• These group of viruses include:
• Arenaviridae
• Filoviridae
• Flaviviridae
• Bunyaviridae

What is Lassa fever?

• An acute haemorrhagic disease caused by Lassa fever virus
• Named after Lassa community in Borno state where it was discovered
• Lassa virus was isolated from two missionary nurses in 1969
• An epidemic prone disease
• Endemic in West Africa- Benin, Ghana, Liberia, Sierra lone, Mali and Nigeria
• But there may be importation of cases into non endemic countries

• Number of Lassa fever infections per year in West Africa is estimated at 300,000-500,000
• Causes about 5000 deaths annually
• CFR is about 1% however in hospitalized patient with severe illness is 15%
• The incident rate in Nigeria is currently unknown
• CFR in Nigeria varies between 3% to 42%
• Largest outbreak in Nigeria was in 2018 affecting about 23 states
• 3,498 suspected cases were reported, 633 confirmed cases, amongst which were 45HCWs
• HCW per case ratio was 7 per 100

Agent:

• Lassa fever virus, a single stranded RNA virus

Host:

• Reservoir host is the multimammate rats
• Mastomys natalensis
• Mastomys erytholeucus
• Hylomyscus pamgi

Environment:

• Poor sanitary conditions
• Deforestation
• Climate changes

Primary transmission- vector to human, occur when people consume infected bush rats or eat items contaminated with the urine/ faeces of infected rats

Secondary transmission- human to human, through exposure to infected person’s fluids

Nosocomial

Sexual transmission

An infected person sheds the virus in his semen for as long as 3months.

Incubation period is 2-21days

• Rural dwellers
• Healthcare workers
• Hunters
• Wild animal consumption
• Poor sanitation
• Low SES
• Pregnant women- it is very lethal in late trimester leading 2% maternal deaths and 80% fetal loss.

• It has a pansystemic effect
• Presentation varies depends on the stage of the illness





• Lassa fever could be classified as:
• Wet LF
• Dry LF
• Wet LF are patients with wet symptoms such as bleeding, diarrhoea
• Dry LF are patients without the wet symptoms such as malaise, headache
• This classification overlaps

Alert case

• Any person with unexplained fever

Suspected case

• Any person with fever >38oC, with 1/more of the aforementioned symptoms.

Probable case

• A suspected case who has one or more the following- hearing loss, seizures, hypotension, oliguria, abnormal bleeding and any of these laboratory features- deranged liver enzymes, decreased platelet count, elevated urea and creatinine

Confirmed case

• A suspected/probable case with a positive PCR result
• Epidemiological linkage to a laboratory confirmed case

Contact definition

• A contact is a person who has been exposed to an infected person or to an infected person’s body fluids
• Within three weeks of last contact with a confirmed or probable case of Lassa fever
• Contacts are divided into 3 categories:
• Category 1- no risk; casual contact
• Category 2- low risk; direct contact with patient
• Category 3- high risk: unprotected exposure to infectious body fluids

• Sensorineural hearing loss- 25% of patients
• Maternal mortality
• Acute Kidney Injury
• Shock
• IUFD
• Transient hair loss
• Gait abnormalities

• Enforcement of policies on good environmental sanitations
• Environmental protection laws- against deforestations
• Health education (food and environmental hygiene)
• Control of vectors- chemical, physical and biological e.g. rodenticides, cats, blockage of holes
• Adherence to IPC protocols e.g. use of PPE by HCWs
• Safe sex practices
• Prompt diagnosis and treatment
• Rehabilitation- provision of hearing aids
• Surveillance

• Poor surveillance system
• Inadequate supplies of PPEs for HCWs
• Limited treatment centres
• Wild game adventures
• Unequipped/ scanty laboratory facilities
• Lack of vaccine
• Risk of bioterrorism
• Culture

• VHFs are majorly endemic in Africa
• Lassa fever, Ebola virus disease and yellow fever are responsible for the major VHFs seen in the continent
• Lack of a suitable vaccine sabotaged the control of VHF
• Research on vaccine development, provision of adequate PPE, and training of HCW on IPC, strengthening of surveillance system, risk communication, international collaboration and response coordination are strongly recommended to help curtail the scourge of VHFs.