Nigeria Army in war Against Rat
After the Ebola crisis of 2014, Nigeria is now facing the spread of
Lassa Fever.
Lassa Alert,
a collective led by Federal Ministry of Health. The Nigeria Center for
Disease Control and Partners are focusing to spreading awareness to help
stop the spread of the disease. Lassa Alert has shared key information
about the disease which has now been confirmed in several states around
Nigeria.
Over 40 people in 10 states have been confirmed dead since this outbreak started.
Key facts
Lassa fever is an acute viral haemorrhagic illness of 1-4 weeks duration that occurs in West Africa.
The Lassa virus is transmitted to humans via contact with food or household items contaminated with rodent urine or faeces.
Person-to-person infections and laboratory transmission can also occur,
particularly in hospitals lacking adequate infection prevent and
control measures.
Lassa fever is known to be endemic in Benin (where
it was diagnosed for the first time in November 2014), Guinea, Liberia,
Sierra Leone and parts of Nigeria, but probably exists in other West
African countries as well.
The overall case-fatality rate is 1%.
Observed case-fatality rate among patients hospitalized with severe
cases of Lassa fever is 15%.
Early supportive care with rehydration and symptomatic treatment improves survival.
Background
Though first described in the 1950s, the virus causing Lassa disease
was not identified until 1969. The virus is a single-stranded RNA virus
belonging to the virus family Arenaviridae.
About
80% of people who become infected with Lassa virus have no symptoms.
One in five infections result in severe disease, where the virus affects
several organs such as the liver, spleen and kidneys.
Lassa
fever is a zoonotic disease, meaning that humans become infected from
contact with infected animals. The animal reservoir, or host, of Lassa
virus is a rodent of the genus Mastomys, commonly known as the
“multimammate rat.” Mastomys rats infected with Lassa virus do not
become ill, but they can shed the virus in their urine and faeces.
Because
the clinical course of the disease is so variable, detection of the
disease in affected patients has been difficult. However, when presence
of the disease is confirmed in a community, prompt isolation of affected
patients, good infection protection and control practices and rigorous
contact tracing can stop outbreaks.
Symptoms of Lassa fever
The
incubation period of Lassa fever ranges from 6-21 days. The onset of
the disease, when it is symptomatic, is usually gradual, starting with
fever, general weakness, and malaise. After a few days, headache, sore
throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and
abdominal pain may follow. In severe cases facial swelling, fluid in
the lung cavity, bleeding from the mouth, nose, vagina or
gastrointestinal tract and low blood pressure may develop. Protein may
be noted in the urine. Shock, seizures, tremor, disorientation, and coma
may be seen in the later stages. Deafness occurs in 25% of patients who
survive the disease. In half of these cases, hearing returns partially
after 1-3 months. Transient hair loss and gait disturbance may occur
during recovery. Death usually occurs within 14 days of onset in fatal
cases. The disease is especially severe late in pregnancy, with maternal
death and/or fetal loss occurring in greater than 80% of cases during
the third trimester.
Transmission
Humans usually become infected with Lassa virus from exposure to urine
or faeces of infected Mastomys rats. Lassa virus may also be spread
between humans through direct contact with the blood, urine, faeces, or
other bodily secretions of a person infected with Lassa fever. There is
no epidemiological evidence supporting airborne spread between humans.
Person-to-person transmission occurs in both community and health-care
settings, where the virus may be spread by contaminated medical
equipment, such as re-used needles. Sexual transmission of Lassa virus
has been reported.
Lassa fever occurs
in all age groups and both sexes. Persons at greatest risk are those
living in rural areas where Mastomys are usually found, especially in
communities with poor sanitation or crowded living conditions. Health
workers are at risk if caring for Lassa fever patients in the absence of
proper barrier nursing and infection control practices.
Diagnosis
Because the symptoms of Lassa fever are so varied and non-specific,
clinical diagnosis is often difficult, especially early in the course of
the disease. Lassa fever is difficult to distinguish from other viral
haemorrhagic fevers such as Ebola virus disease; and many other diseases
that cause fever, including malaria, shigellosis, typhoid fever and
yellow fever.
Definitive diagnosis
requires testing that is available only in specialized laboratories.
Laboratory specimens may be hazardous and must be handled with extreme
care. Lassa virus infections can only be diagnosed definitively in the
laboratory using the following tests:
antibody enzyme-linked immunosorbent assay (ELISA)
antigen detection tests
reverse transcriptase polymerase chain reaction (RT-PCR) assay
virus isolation by cell culture.
Treatment and vaccines
The antiviral drug ribavirin seems to be an effective treatment for
Lassa fever if given early on in the course of clinical illness. There
is no evidence to support the role of ribavirin as post-exposure
prophylactic treatment for Lassa fever.
There is currently no vaccine that protects against Lassa fever.
Prevention and control
Prevention
of Lassa fever relies on promoting good “community hygiene” to
discourage rodents from entering homes. Effective measures include
storing grain and other foodstuffs in rodent-proof containers, disposing
of garbage far from the home, maintaining clean households and keeping
cats. Because Mastomys are so abundant in endemic areas, it is not
possible to completely eliminate them from the environment. Family
members should always be careful to avoid contact with blood and body
fluids while caring for sick persons.
In
health-care settings, staff should always apply standard infection
prevention and control precautions when caring for patients, regardless
of their presumed diagnosis. These include basic hand hygiene,
respiratory hygiene, use of personal protective equipment (to block
splashes or other contact with infected materials), safe injection
practices and safe burial practices.
Health
workers caring for patients with suspected or confirmed Lassa fever
should apply extra infection control measures to prevent contact with
the patient’s blood and body fluids and contaminated surfaces or
materials such as clothing and bedding. When in close contact (within 1
metre) of patients with Lassa fever, health-care workers should wear
face protection (a face shield or a medical mask and goggles), a clean,
non-sterile long-sleeved gown, and gloves (sterile gloves for some
procedures).
Laboratory workers are
also at risk. Samples taken from humans and animals for investigation of
Lassa virus infection should be handled by trained staff and processed
in suitably equipped laboratories.
On
rare occasions, travellers from areas where Lassa fever is endemic
export the disease to other countries. Although malaria, typhoid fever,
and many other tropical infections are much more common, the diagnosis
of Lassa fever should be considered in febrile patients returning from
West Africa, especially if they have had exposures in rural areas or
hospitals in countries where Lassa fever is known to be endemic.
Health-care workers seeing a patient suspected to have Lassa fever
should immediately contact local and national experts for advice and to
arrange for laboratory testing.
WHO response
The Ministries of Health of Guinea, Liberia and Sierra Leone, WHO, the
Office of United States Foreign Disaster Assistance, the United Nations,
and other partners have worked together to establish the Mano River
Union Lassa Fever Network. The programme supports these 3 countries in
developing national prevention strategies and enhancing laboratory
diagnostics for Lassa fever and other dangerous diseases. Training in
laboratory diagnosis, clinical management, and environmental control is
also included. In addition, a new ward dedicated to the care of patients
with Lassa fever is under construction in Sierra Leone, sponsored by
the European Union