the presentation is about Lassa fever

1. Lassa fever
MBEDZI DP

2. Introduction
 Lassa fever is a viral haemorrhagic fever transmitted by rats.
 It has been known since the 1950s, but the virus was not identified until 1969,
when two missionary nurses died from it in the town known as Lassa in Nigeria.
 Found predominantly in west Africa, it has the potential to cause tens of thousands
of deaths.
 Even after recovery, the virus remains in body fluids, including semen.
 The years of civil unrest in Sierra Leone (1991-2002) halted the investigation
(through international collaboration) of Lassa fever at a specialist unit in Kenema
(Lecompte et al., 2006).
 Increasing international travel and the possibility of use of the Lassa virus as a
biological weapon escalate the potential for harm beyond the local level.
 Access to the country is improving, so renewed efforts to understand it are
feasible.

3. Epidemiology
 Lassa fever is caused by a single stranded RNA virus and is a disseminated
systemic primary viral infection.
 The main feature of fatal illness is impaired or delayed cellular immunity leading to
fulminant viraemia.
 The prevalence of antibodies to the virus in the population is 8-52% in Sierra
Leone, 4-55% in Guinea, and 21% in Nigeria.
 Seropositivity has also been found in the Central African Republic, Democratic
Republic of the Congo, Mali, and Senegal.
 Staff from the UK Department for International Development, the International
Committee of the Red Cross, and the United Nations Mission in Sierra Leone
have succumbed.
 Sporadic cases have occurred in travellers returning to Britain, the Netherlands,
and Germany (Asogun et al., 2019).

4. Transmission
 Once a Mastomys rat is infected with the virus, it can excrete the virus in its
faeces and urine, potentially for the rest of its life.
 As a result, the virus can spread easily, especially as the rats breed rapidly and
can inhabit human homes.
 The most common method of transmission is by consuming or inhaling rat urine or
faeces. It can also be spread through cuts and open sores.
 The rats live in and around human habitation, and they often encounter foodstuffs.
Sometimes people eat the rats, and the disease can be spread during their
preparation.
 Person-to-person contact is possible via blood, tissue, secretions or excretions,
but not through touch. Sharing needles may spread the virus, and there are some
reports of sexual transmission.
 Lassa fever can also be passed between patients and staff at poorly equipped
hospitals where sterilization and protective clothing is not standard.

5. Pathogenesis
 On acquisition of the virus through contact with infected rodent urine, saliva, respiratory
secretion and blood, Lassa fever infection is initiated in the victim.
 Lassa fever is a generalised infection with haemorrhagic dissemination of the virus to
multiple organs and systems via the blood stream, lymph vessels, respiratory tract, and/or
digestive tract.
 The blood vessels are always the most affected and the virus multiplies in cells of the
reticuloendothelial system causing capillary lesions.
 The capillary permeability is increased, followed by peripheral vasoconstriction with the
presence of disseminated intravascular coagulation that leads to haemorrhagic
syndrome.
 Haemorrhage may be present in the intestine, liver, myocardium, lungs and the brain and
are often inflamed and enlarged, and the tissues are infiltrated, lesioned and necrotic.
 Other observable pathological changes include black vomit with traces of blood, watery
diarrhoea that gives rise to dehydration and reduction in the volume of blood in circulation
and low blood pressure, depressed lymphocyte counts and platelet function as well as
moderate thrombocytopenia.

6. Clinical manifestation
 Symptoms generally appear within 6 to 21 days after infection occurs.
 An estimated 80% of infections do not produce significant symptoms, although
there may be a general malaise, headache, and a slight fever.
 In the remaining 20% of cases, Lassa fever becomes serious.
Symptoms can include:
 bleeding in the gums, nose, eyes, or elsewhere,
 difficulty breathing, coughing,
 swollen airways, vomiting and diarrhoea, both with blood,
 difficulty swallowing,
 hepatitis,
 swollen face

7. Table 1: Showing clinical manifestation and their stages.

8. Diagnosis
 The symptoms of Lassa fever vary widely, and diagnosis can be difficult.
 Clinically, the disease can resemble other viral haemorrhagic fevers, including the
Ebola virus, malaria, and typhoid.
 The only definitive tests for Lassa fever are laboratory-based, and the handling of
specimens can be hazardous. Only specialized institutions can conduct these tests
(Asogun et al., 2012).
 Lassa fever is generally diagnosed by using enzyme-linked immunosorbent
serologic assays (ELISA). These detect IgM and IgG antibodies and Lassa
antigens.
 Reverse transcription-polymerase chain reaction (RT-PCR) can also be used in the
early stages of the disease.

9. Prevention
 Primary transmission of the Lassa virus from its host to humans can be prevented by
avoiding contact with Mastomys rodents, especially in the geographic regions where
outbreaks occur.
 Putting food away in rodent-proof containers and keeping the home clean help to
discourage rodents from entering homes.
 When caring for patients with Lassa fever, further transmission of the disease through
person-to-person contact or nosocomial routes can be avoided by taking preventive
precautions against contact with patient secretions (called VHF isolation precautions or
barrier nursing methods).
 Such precautions include wearing protective clothing, such as masks, gloves, gowns,
and goggles; using infection control measures, such as complete equipment sterilization;
and isolating infected patients from contact with unprotected persons until the disease
has run its course (Asogun et al., 2019).
 Furthermore, educating people in high-risk areas about ways to decrease rodent
populations in their homes will aid in the control and prevention of Lassa fever.

10. Figure 1: Showing protective clothing worn when dealing with Lassa fever patients

11. Complications
 In around 1% of all cases, Lassa fever is fatal, and around 15 to 20% of all
hospitalizations for the disease will end in death.
 Death can occur within 2 weeks after the onset of symptoms due to multiple organ
failure.
 One of the most common complications of Lassa fever is hearing loss, which
occurs in around 1 in 3 infections.
 It varies in degree and is not necessarily related to the severity of the symptoms.
Deafness caused by Lassa fever can be permanent.
 It is particularly dangerous for women in the third trimester of pregnancy.
Spontaneous loss of pregnancy occurs in around 95% of pregnancies.

12. Treatment
 Ribavirin, an antiviral drug, has been used with success in Lassa fever patients.
 It has been shown to be most effective when given early in the course of the
illness.
 Patients should also receive supportive care consisting of maintenance of
appropriate fluid and electrolyte balance, oxygenation and blood pressure, as well
as treatment of any other complicating infections.

13. Conclusion
 The Mastomys rat is so widespread that it cannot realistically be eradicated. As a
result, the main aim is to avoid these rodents and prevent them from sharing
human habitation.
 The World Health Organization (WHO) and other organizations work to raise
awareness in areas where Lassa fever is a threat.

14. References
 Asogun DA, Adomeh DI, Ehimuan J, et al. Molecular diagnostics for Lassa Fever at Irrua
specialist teaching hospital, Nigeria: lessons learnt from two years of laboratory operation.
PLoS Neglected Tropical Diseases. 2012;6(9):e1839.
 Asogun, D.A., Günther, S., Akpede, G.O., Ihekweazu, C. and Zumla, A., 2019. Lassa
fever: epidemiology, clinical features, diagnosis, management and prevention. Infectious
Disease Clinics, 33(4), pp.933-951.
 Imported Lassa fever. New Jersey: Centers for Disease Control and Prevention (CDC)
2004. MMWR Morb Mortal Wkly Rep 2004; 53(38): 894–7.
 Lecompte E, Fichet-Calvet E, Daffis S, et al. Mastomys natalensis and Lassa fever, West
Africa. Emerging Infectious Diseases. 2006;12(12):1971-4.
 Ter Meulen J, Lenz O, Koivogui L, Magassouba N, Kaushik SK, Lewis R, et al. Short
communication: Lassa fever in Sierra Leone: UN peacekeepers are at risk. Trop Med Int
Health 2001;6: 83-4.