As I had mentioned yesterday
in this column, we will be covering about the priority diseases as revised by
the World Health Organization (WHO). The first to be covered is Lassa fever.
Here are some salient facts
about Lassa fever.
· Lassa fever is an acute viral
hemorrhagic illness caused by Lassa virus, a
member of the Arenavirus family of viruses.
· Lassa virus is endemic in Benin, Ghana,
Guinea, Liberia, Mali, Sierra Leone, and Nigeria and other countries in West
Africa.
· It is a zoonotic disease.
Rodents (multimammate rats) are the animal reservoirs and shed the virus in
their urine and feces.
· Humans acquire the infection
from contact with infected rodents through rodent urine or feces, inhalation of
aerosolized rodent excretions, or consumption of infected rodents as a food
source.
· Person-to-person transmission
can occur through direct contact with infectious
body fluids (e. g., blood, urine, pharyngeal secretions, vomitus, or other body
secretions),
unprotected contact with potentially infectious material (e.g., touching
vomitus) and mucosal exposure from splashes of body fluids.
· Infection does not spread via
casual contact such as hugging, shaking hands, or sitting near someone.
· Persons with Lassa fever
infection are not believed to be contagious prior to symptom onset.
· The incubation period of Lassa
fever is about 10 days (range 6-21 days).
· Clinical picture: Gradual onset of symptoms in
most patients. Symptoms are mild to begin with viz. low-grade fever, general
weakness, malaise and so may be ignored. These are followed by headache, sore
throat, muscle pain, chest pain, nausea, vomiting, diarrhea, cough, and
abdominal pain. In severe disease, facial swelling, fluid in the lung cavity,
bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood
pressure are present. Later stage may be characterized by shock, seizures,
tremor, disorientation and coma.
· In fatal cases, death usually
occurs within 14 days on onset of illness.
· The most common complication
of Lassa fever is deafness, which may occur following either mild or severe
illness.
· Lassa fever
is difficult to distinguish from other febrile illnesses, including malaria,
shigellosis, typhoid fever, yellow fever and other viral hemorrhagic
fevers.
· The overall case-fatality rate
is 1%, while in hospitalized patients, the case-fatality rate is 15%.
· Diagnosis is usually supported
by a relevant history of exposure along with suggestive signs and symptoms.
· Confirmatory test: ELISA to
detect IgM and IgG antibodis and Lassa antigen. Serum IgM is detectable 10 to
21 days after symptom onset; serum IgG is detectable approximately 21 days
after symptom onset. Serum reverse-transcription polymerase chain reaction is
the preferred diagnostic tool but is expensive and requires technical
expertise.
· Early supportive care with
rehydration and symptomatic treatment improves survival
· Treatment in confirmed cases:
IV ribavirin (Grade 1B); ribavirin may be administered orally, if
IV ribavirin is not available.
o
IV ribavirin:
30 mg/kg (maximum 2 g) loading dose followed by 15 mg/kg (1
g max) IV 4-6 hourly x 4 days, followed by 7.5 mg/kg IV (500 mg max)
8 hourly x 6 days
o
Oral
ribavirin: 35 mg/kg (2.5 g max), followed by 15 mg/kg (1 g
max) orally 6 hourly x 4 days, followed by 15 mg/kg (1 g max) 8
hourly x 6 days
· Prevention
o
Avoiding
rodents (multimammate rats).
o
Consider all
patients as infectious even if signs and symptoms are mild.
o
All standard,
contact, and droplet precautions as well as correct use of appropriate personal
protective equipment should be strictly adhered to.
o
Blood and
body fluid specimens from patients with suspected Lassa fever infection should
be considered highly infectious. Caution should be exercised when handling such
material.
o
Postexposure
prophylaxis with oral ribavirin for contacts with known or suspected
Lassa fever infection with risk factors for transmission such as penetrating
needle stick injury, exposure of mucous membranes or broken skin to blood or
body fluids, and participation in procedures involving exposure to bodily
fluids or respiratory secretions without use of personal protective equipment.
· There is
currently no vaccine that protects against Lassa fever
(Source: Uptodate, WHO)
Dr
KK Aggarwal
Padma
Shri Awardee
Vice President CMAAO
Group Editor-in-Chief IJCP Publications
Vice President CMAAO
Group Editor-in-Chief IJCP Publications
President
Heart Care Foundation of India
Immediate
Past National President IMA