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LASSA FEVER
VIRUS DISEASE:THE
FOE OF A FRIEND
��SINCE 1969��
DR M.O. DAODU
B.SC., MBBS(BENIN)
UNIBEN/UBTH
31/01/20162/1/2016 1

OUTLINE
? INTRODUCTION
? THE VIRUS
? THE RAT
? TRANSMISSION
? DISTRIBUTION
? SYMPTOMS AND SIGNS
? DIAGNOSIS
? TREATMENT
? PREVENTION
? CONCLUSION2/1/2016 2

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.
2/1/2016 3

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)2/1/2016 4

THE RAT
THE FRIEND ADDIND TO BLOOD THEN THE MONSTER PUSHING BLLOD OUT2/1/2016 6

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.2/1/2016 7

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.2/1/2016 8

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.
2/1/2016 9

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.
2/1/2016 10

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.
2/1/2016 11

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 C?te
d��Ivoire and Burkina Faso and there is serologic
evidence of Lassa virus infection in Togo and Benin.
2/1/2016 12

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.
2/1/2016 13

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.
2/1/2016 14

DISTRIBUTION MAP...
2/1/2016 15

DISTRIBUTION MAP...
2/1/2016 16

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%�C20%.
? 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.
2/1/2016 17

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.
2/1/2016 18

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.
2/1/2016 19

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.
2/1/2016 20

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.
2/1/2016 21

DISTRIBUTION MAP...
2/1/2016 23

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.
2/1/2016 24

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).
2/1/2016 25

SYMPTOMS AND SIGNS...
2/1/2016 26

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.2/1/2016 27

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.
2/1/2016 28

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.
2/1/2016 29

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.
2/1/2016 30

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).
2/1/2016 31

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.
2/1/2016 32

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.
2/1/2016 33

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LASSA FEVER, THE FOE TO AFRIEND SINCE 1969

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