05/01/2023 1

LASSA FEVER VIRUS DISEASE:THE

FOE OF A FRIEND‘SINCE 1969’

DR M.O. DAODUB.SC., MBBS(BENIN)

UNIBEN/UBTH31/01/2016

05/01/2023 2

OUTLINE• INTRODUCTION• THE VIRUS• THE RAT• TRANSMISSION• DISTRIBUTION• SYMPTOMS AND SIGNS• DIAGNOSIS• TREATMENT• PREVENTION• CONCLUSION

05/01/2023 3

INTRODUCTION

• Lassa fever is an acute viral illness that occurs in west Africa.

• The illness was discovered in 1969 when two missionary nurses died in Nigeria.

• The virus is named after the town-LASSA, IN BORNU STATE in Nigeria where the first cases occurred.

• These cases were from two missionary health workers who died from contacts with ill persons.

05/01/2023 4

THE VIRUS• The virus, a member of the virus family Arenaviridae,

is a single-stranded RNA virus and is zoonotic, or animal-borne.

• Viral hemorrhagic fevers (VHFs) are caused by several families of enveloped RNA viruses: filoviruses (Ebola and Marburg hemorrhagic fever), arenaviruses (Lassa fever, Lujo, Guanarito, Machupo, Junin, Sabia, and Chapare viruses), bunyaviruses (Rift Valley fever [RVF], Crimean-Congo hemorrhagic fever [CCHF], and hantaviruses), and flaviviruses (dengue, yellow fever, Omsk hemorrhagic fever, Kyasanur Forest disease, and Alkhurma viruses)

05/01/2023 5

THE VIRUS...

05/01/2023 6

THE RAT

THE FRIEND ADDIND TO BLOOD THEN THE MONSTER PUSHING BLLOD OUT

05/01/2023 7

THE RAT...• The reservoir, or host, of Lassa virus is a rodent known

as the "multimammate rat" (Mastomys natalensis). • Once infected, this rodent is able to excrete virus in

urine for an extended time period, maybe for the rest of its life.

• Mastomys rodents breed frequently, produce large numbers of offspring, and are numerous in the savannas and forests of west, central, and east Africa. In addition, Mastomys readily colonize human homes and areas where food is stored. All of these factors contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.

05/01/2023 8

TRANSMISSION• Transmission of Lassa virus to humans occurs most

commonly through ingestion or inhalation.• Mastomys rodents shed the virus in urine and droppings

and direct contact with these materials, through touching soiled objects, eating contaminated food, or exposure to open cuts or sores, can lead to infection. Because Mastomys rodents often live in and around homes and scavenge on leftover human food items or poorly stored food, direct contact transmission is common.

• Mastomys rodents are sometimes consumed as a food source and infection may occur when rodents are caught and prepared.

05/01/2023 9

TRANSMISSION...• Contact with the virus may also occur when a

person inhales tiny particles in the air contaminated with infected rodent excretions. This aerosol or airborne transmission may occur during cleaning activities, such as sweeping.

• Direct contact with infected rodents is not the only way in which people are infected; person-to-person transmission may occur after exposure to virus in the blood, tissue, secretions, or excretions of a Lassa virus-infected individual.

05/01/2023 10

TRANSMISSION...• Casual contact (including skin-to-skin contact

without exchange of body fluids) does not spread Lassa virus.

• Person-to-person transmission is common in health care settings (called nosocomial transmission) where proper personal protective equipment (PPE) is not available or not used.

• Lassa virus may be spread in contaminated medical equipment, such as reused needles.

05/01/2023 11

DISTRIBUTION

• Lassa fever is endemic in parts of west Africa including Sierra Leone, Liberia, Guinea and Nigeria.

• However, other neighboring countries are also at risk, as the animal vector for Lassa virus, the "multimammate rat" (Mastomys natalensis) is distributed throughout the region.

05/01/2023 12

DISTRIBUTION...

• In 2009, the first case from Mali was reported in a traveler living in southern Mali; Ghana reported its first cases in late 2011.

• Isolated cases have also been reported in Côte d’Ivoire and Burkina Faso and there is serologic evidence of Lassa virus infection in Togo and Benin.

05/01/2023 13

DISTRIBUTION...

• The number of Lassa virus infections per year in west Africa is estimated at 100,000 to 300,000, with approximately 5,000 deaths.

• Unfortunately, such estimates are crude, because surveillance for cases of the disease is not uniformly performed.

05/01/2023 14

DISTRIBUTION...

• In some areas of Sierra Leone and Liberia, it is known that 10%-16% of people admitted to hospitals every year have Lassa fever, which indicates the serious impact of the disease on the population of this region.

05/01/2023 15

DISTRIBUTION MAP...

05/01/2023 16

DISTRIBUTION MAP...

05/01/2023 17

DISTRIBUTION...• Lassa fever is endemic in Nigeria and causes

outbreaks almost every year in different parts of the country, with yearly peaks observed between December and February.

• The case-fatality rate in hospitalized px is10%–20%. • Investigations in the 1970s and 1980s pointed to the

existence of 3 disease-endemic zones within Nigeria: the NE region around Lassa, the central region around Jos, and the southern region around Onitsha.

05/01/2023 18

DISTRIBUTION...• From 2005 through 2008, 10 cases of Lassa fever

were confirmed by virus detection• Cases 7 to 10 occurred in Abuja and Jos from

December 2007 through March 2008• Between August 2015 and 23 January 2016, 159

suspected cases of Lassa fever, including 82 deaths, were reported across 19 states.

• Investigations are ongoing and a retrospective review of cases is currently being performed; therefore, these figures are subject to change.

05/01/2023 19

DISTRIBUTION...

• The 4 most affected states are Bauchi, Edo, Oyo and Taraba, which account for 54% of the confirmed cases (n=54) and 52% of the reported deaths (n=34). The remaining 15 States have reported less than 5 confirmed cases.

• Samples of 54 cases, including 34 deaths, were confirmed for Lassa fever by reverse transcription polymerase-chain reaction (RT-PCR). All samples tested negative for Ebola virus disease, Dengue and yellow fever.

05/01/2023 20

DISTRIBUTION...

• To date, 4 health care workers were laboratory-confirmed for Lassa fever; of these 4 cases, 2 passed away.

• As of 21 January, 2,504 contacts had been listed and 1,942 are currently being monitored.

• A total of 562 contacts have completed follow up. So far, none of the contacts have tested positive for Lassa fever.

05/01/2023 21

DISTRIBUTION...• Another report says:On 14 January, official records

states at least 140 suspected cases and 30 confirmed cases, including 53 deaths, in 14 states indicating a case fatality rate of 37.9%

• As of 20 January, local media has reported as many as 212 suspected cases and 63 deaths in 17 states.

• The number of suspected cases of Lassa fever has reached 212 across 17 states, the Minister of Health confirmed. As of 19 January, there were 76 fatalities.

05/01/2023 22

DISTRIBUTION MAP

05/01/2023 23

DISTRIBUTION MAP...

05/01/2023 24

SYMPTOMS AND SIGNS

• Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus.

• For the majority of Lassa fever virus infections (approximately 80%), symptoms are mild and are undiagnosedMild symptoms include slight fever, general malaise and weakness, and headache.

05/01/2023 25

SYMPTOMS AND SIGNS...• In 20% of infected individuals, however, disease

may progress to more serious symptoms including respiratory distress, repeated vomiting, facial swelling, pain in the chest, back, and abdomen.

• More severe symptoms include: diarrhoea,bleeding (from eyes, nose, mouth(gums), anus, vaginal, pennis).

• Pulmonary oedema, encephalitis, hearing loss and shock(loss of consciousness).

05/01/2023 26

SYMPTOMS AND SIGNS...

05/01/2023 27

DIAGNOSIS• Lassa fever is most often diagnosed by using enzyme-

linked immunosorbent serologic assays (ELISA), which detect IgM and IgG antibodies as well as Lassa antigen.

• Reverse transcription-polymerase chain reaction (RT-PCR) can be used in the early stage of disease.

• The virus itself may be cultured in 7 to 10 days, this procedure should only be done in a high containment laboratory with good laboratory practices.

• Immunohistochemistry, performed on formalin-fixed tissue specimens, can be used to make a postmortem diagnosis.

05/01/2023 28

TREATMENT

• It is better when detected early• Supportive care is with fluid, treatment of

symptoms and Oxygen therapy.• Ribavirin is the anti-viral agent which has been

shown to be most effective when given early in the course of the illness.

• Effective management of the complications is important.

05/01/2023 29

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.

05/01/2023 30

PREVENTION...

• Using these rodents as a food source is not recommended.

• Trapping in and around homes can help reduce rodent populations;

• However, the wide distribution of Mastomys in Africa makes complete control of this rodent reservoir impractical.

05/01/2023 31

PREVENTION...

• 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).

05/01/2023 32

PREVENTION...

• Such precautions include wearing personal protective equipment (PPE): protective clothing, such as masks, gloves, gowns and goggles and safety shoes

• Using infection control measures, such as complete equipment sterilization Isolating infected patients from contact with unprotected persons until the disease has run its course.

05/01/2023 33

CONCLUSION

• The rat is a palatable meal particularly among the resource poor population: a friend

• It carries a deadly virus which is responsible for tension, illness and death among Nigerians and other West African countries: a foe.

• It is sad to lose a palatable meal to a rat but sadder when loved ones lose you to a rat.

05/01/2023 34

THANK YOU !