What is Lassa Fever?
Lassa
fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of
the arenavirus family of viruses. It is transmitted to humans from contacts
with food or household items contaminated with rodent excreta. The disease is
endemic in the rodent population in parts of West Africa. Person-to-person
infections and laboratory transmission can also occur, particularly in the
hospital environment in the absence of adequate infection control measures.
fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of
the arenavirus family of viruses. It is transmitted to humans from contacts
with food or household items contaminated with rodent excreta. The disease is
endemic in the rodent population in parts of West Africa. Person-to-person
infections and laboratory transmission can also occur, particularly in the
hospital environment in the absence of adequate infection control measures.
Transmission
of Lassa Fever
of Lassa Fever
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.
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.
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.
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.
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.
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.
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. 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.
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. 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.
Signs
and Symptoms of Lassa Fever
and Symptoms of Lassa Fever
After
an incubation period of six to 21 days,
an acute illness develops. Nonspecific symptoms
include fever,
facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal
bleeding. The other symptoms arising from the affected organs are:
an incubation period of six to 21 days,
an acute illness develops. Nonspecific symptoms
include fever,
facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal
bleeding. The other symptoms arising from the affected organs are:
·
Nausea
Nausea
·
Vomiting (bloody)
Vomiting (bloody)
·
Diarrhea (bloody)
Diarrhea (bloody)
·
Stomach ache
Stomach ache
·
Constipation
Constipation
·
Hypertension
Hypertension
·
Cough, etc.
Cough, etc.
Control Measures for Lassa Fever
·
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.
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.
Putting food away in rodent-proof containers and
keeping the home clean help to discourage rodents from entering homes.
·
Using these rodents as a food source is not
recommended.
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.
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.
·
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).
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.
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.
·
Further, 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.
Further, 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.
