Published Date: 2010-10-17 18:00:04
Subject: PRO/AH/EDR> Lassa fever - Sierra Leone (03): (NO)
Archive Number: 20101017.3770
LASSA FEVER - SIERRA LEONE (03): (NORTHERN)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Sun 17 Oct 2010
From: Daniel Bausch <email@example.com>
re: Lassa fever -- Sierra Leone (02): (NO) 20101008.3662
We are writing to provide further information regarding the recent postings
on Lassa fever in Sierra Leone:
1. The index case was a 17 year old pregnant woman who delivered at 28
weeks gestational age. Both she and the baby (not a 6 year old) died.
Although she and her family occasionally caught and consumed rodents, there
is no history of her running a "rat meat restaurant".
2. In all, there were 35 identified contacts of this woman and child, but
only 4 developed Lassa fever. All had direct contact with the index case or
secondary cases, and all 4 survived. We have not identified any more cases,
and, since the time from the last known contact of any of the confirmed
cases has now exceeded the 3-week maximum incubation period for Lassa
fever, we do not anticipate more cases related to this particular chain of
3. Whether "the disease has migrated from the forest region of the east to
the savannah grasslands of the north" is a very open question. The index
case denied travel to the known endemic area in the east, but it is always
possible that the infection resulted from unrecognized contact from an
infected person coming from the east to her village in Bombali District.
Our zoology team is presently trapping rodents in the home and village of
the index case. Identification of Lassa virus-positive _Mastomys
natalensis_ would confirm the notion that the endemic area has expanded.
However, it should be noted that suspected cases of Lassa fever have been
reported from this area before, but laboratory facilities were not
available at the time to confirm them.
4. There has indeed been a significant increase in reported cases of Lassa
fever in Sierra Leone over the last 9 months or so. However, this
observation largely coincides with the implementation of Sierra Leone's new
policy of providing free care to children under 5 and pregnant and
lactating mothers (<http://news.bbc.co.uk/2/hi/8645968.stm>). The numbers
of patients seen in hospitals and health clinics sky-rocketed, driving
upward the perceived incidence of virtually every disease that affects
these groups, including Lassa fever. Whether the observed increase in cases
of Lassa fever is purely reflective of the change in policy or also has
concomitant biological determinants is unknown. It should also be noted
that, for reasons unknown, there is significant seasonal and yearly
fluctuation in the incidence of Lassa fever.
Foday Dafae, MD
National Disease Surveillance Coordinator, Sierra Leone
Ministry of Health and Sanitation
Lassa Fever Surveillance Coordinator, Eastern Province,
Sierra Leone Ministry of Health and Sanitation
Daniel Bausch, MD, MPH&TM
Director, Tulane University Research and Training Program in the Mano River
Union Countries of West Africa
[ProMED-mail thanks Daniel Bausch and colleagues for these valuable
first-hand observations on the Lassa fever situation in the Northern region
of Sierra Leone, and for correcting some aspects of the previous report.
The HealthMap/ProMED-mail interactive map of Sierra Leone is available at
<http://healthmap.org/r/0bj5>. - Mod.CP]