Wednesday, July 11, 2018

PRO/AH/EDR> Lassa fever - West Africa (37): Liberia, WHO

LASSA FEVER - WEST AFRICA (37): LIBERIA, WHO
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Date: Fri 6 Jul 2018, 5:00 PM
Source: WHO Weekly Bulletin on Outbreaks and Other Emergencies
[edited]
<http://apps.who.int/iris/bitstream/handle/10665/273028/OEW27-300606072018.pdf?sequence=1&isAllowed=y>


Event Description
-----------------
Liberia has continued to experience sporadic cases of Lassa fever
since the beginning of 2018. In week 25 (week ending 26 Jun 2018), 2
new confirmed Lassa fever cases were reported in Nimba County, the
only county with active transmission currently. Nimba County has
reported 5 confirmed Lassa fever cases since [12 May 2018]. In the
latest event (the 2 confirmed cases in week 25), the 1st case-patient,
a 59-year- old male from Gbehlay Geh district, fell ill on [4 Jun
2018] and was treated with antimalarials and antibiotics at a local
clinic. On [20 Jun 2018], the case-patient presented to a public
hospital with fever and other constitutional symptoms, and had
bleeding from a venepuncture site. On [21 Jun 2018], a blood specimen
was collected and sent to the National Public Health Reference
Laboratory (NPHRL). The test result released on [26 Jun 2018] was
positive for Lassa fever virus infection. The 2nd case-patient, a
41-year-old female, is the wife of the first case-patient (described
above). She developed illness on [17 Jun 2018] and was admitted to the
same hospital on [20 June 2018] with fever and other constitutional
symptoms. Being a known contact, a blood specimen was collected on [21
Jun 2018] and the test result released on [26 Jun 2018] was positive
for Lassa fever. The 2 case-patients are admitted under barrier
nursing and ribavirin treatment initiated. A total of 26 contacts,
including 13 health workers, have been line listed and are being
followed up.

Between [1 Jan 2018] and [27 Jun 2018], a total of 130 suspected Lassa
fever cases, including 33 deaths, were reported. Of these, 20 cases
were laboratory confirmed, 103 were discarded (after testing
negative), and 7 cases were not tested due to inadequate specimens. Of
the 20 confirmed cases, 14 have died, giving a case fatality rate of
70 percent. Females make up 60 percent (12) of the confirmed cases.
The age range for the confirmed cases is 1 to 65 years old, with a
median of 32.5 years. The confirmed cases are from 5 counties, namely
(Nimba (9), Bong (4), Montserrado (3), Margibi (2), and Grand Bassa
(2).

Public Health Actions
---------------------
- The Ministry of Health and the National Public Health Institute of
Liberia (NPHIL) are coordinating response activities to the Lassa
fever outbreak, with support from WHO, CDC and other partners. The
national epidemic preparedness and response committee (NEPRC), under
the leadership of NPHIL, have been meeting weekly to review the Lassa
fever outbreak situation and provide technical support to sub-national
level, with technical support from WHO, and US-CDC; 15 WHO field
offices are providing technical and operational support to the
response.
- Active surveillance, including case search, case investigation and
contact tracing are ongoing in the affected districts. A specimen
transport system using couriers is available at designated points
across the country to transport specimens to the NPHRL for testing.
- The Ganta United Methodist Hospital has been designated as a
treatment centre, and equipped with ribavirin and other medical
supplies for case management. Orientation of healthcare workers on
case management protocol is ongoing.
- Healthcare workers in the country are being trained on Lassa fever
case management and infection prevention and control (IPC) measures by
NPHIL and MOH, with support from WHO.
- Health workers' exposure risk assessment is planned to be conducted
in the clinic or hospital where the confirmed cases sought care.
- Community engagement activities are ongoing in the affected
communities, including home visits and providing information on
environmental cleanliness.

Situation Interpretation
------------------------
Sporadic Lassa fever cases continue to occur in certain parts of
Liberia where the disease is known to be endemic. Bong, Grand Bassa,
Margibi, and Nimba are among the counties that report cases annually.
In 2017, a total of 30 confirmed cases were reported from 7 counties.
The reason for these sporadic cases is known: the constant interaction
of rats (the vector for Lassa fever virus) and people in unsanitary
conditions. The national authorities and partners need to prioritize
measures mitigating this exposure risk factor by improving vector and
environmental management components of the response. This goes along
with effective social mobilization and community engagement
strategies, targeting vector control and environmental management in
the communities. There is also a need to enhance capacity at the
subnational levels for early case detection, case investigation,
appropriate case management and its associated IPC [infection
prevention and control] measures aimed at averting infection among
health workers.

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[The number of Lassa fever cases in Liberia continues to slowly
increase. Between 1 Jan 2018 and 27 Jun 2018, 20 cases were laboratory
confirmed, up from 18 cases on 1 Jun 2018. Apparently, all these Lassa
fever virus infections were acquired by contact with infected rodents
or their excretions. Lassa fever virus can be acquired from infected
rodents or patients in the hospital but in the above report, there is
no mention of Lassa fever virus nosocomial transmission. Transmission
can occur in health facilities when personal protective equipment is
not employed and barrier-nursing practices are not adequate to protect
staff from blood and secretions of infected patients. The hospitals
attending the patients mentioned above do have barrier measures in
place.

As mentioned in previous posts, Lassa fever virus transmission to
humans occur when people are in contact with the reservoir rodent
host, the multimammate mouse (_Mastomys natalensis_ and _M.
erythroleucus_) and the African wood mouse (_Hylomycus pamfi_) or
their excreta, as was likely the situation in these cases. Rodent
control has to be undertaken at the village level with individual
households employing the preventive measures listed above. This
requires an extensive and continuous public education effort.

Images of the _Mastomys natalensis_ mouse, the rodent reservoir of
Lassa fever virus, can be seen at
<https://www.inaturalist.org/taxa/45326-Mastomys-natalensis> and of
_M. erythroleucus_ and _Hylomycus pamfi_ at:
<http://punchng.com/nigerias-large-rat-population-threatens-lassa-fever-war/>.
- Mod.TY

Maps of Liberia can be accessed at:
<http://www.theworldmap.net/country/big/liberia/> and
<http://healthmap.org/promed/p/54>]

[See Also:
Lassa fever - West Africa (33): Liberia
http://promedmail.org/post/20180615.5858754
Lassa fever - West Africa (30): Liberia
http://promedmail.org/post/20180604.5836574
Lassa fever - West Africa (28): Liberia
http://promedmail.org/post/20180520.5806477
Lassa fever - West Africa (27): Liberia (MG)
http://promedmail.org/post/20180510.5791763
Lassa fever - West Africa (23): Liberia, WHO
http://promedmail.org/post/20180417.5753003
Lassa fever - West Africa (17): Liberia (MO, NI)
http://promedmail.org/post/20180310.5678669
2017
----
Lassa fever - West Africa (04): Liberia
http://promedmail.org/post/20170209.4827934
2016
----
Lassa fever - West Africa (29): Nigeria, Liberia
http://promedmail.org/post/20160520.4233773
Lassa fever - West Africa (23): Sweden (VG) ex Liberia, additional
information http://promedmail.org/post/20160406.4141321
2015
----
Lassa fever - USA: (NJ) ex Liberia
http://promedmail.org/post/20150526.3386913
2014
----
Lassa fever - Nigeria, Liberia
http://promedmail.org/post/20140328.2363217
2013
---
Lassa fever - Liberia: (BG) fatal cases
http://promedmail.org/post/20130911.1937742
2007
----
Lassa fever - Liberia (03) http://promedmail.org/post/20070430.1406
Lassa fever - Liberia (02): confirmed
http://promedmail.org/post/20070413.1235
Lassa Fever - Liberia: RFI http://promedmail.org/post/20070410.1210
2006
----
Lassa fever - Liberia (02) http://promedmail.org/post/20061001.2812
Lassa fever - Liberia: RFI http://promedmail.org/post/20060929.2783
2004
----
Lassa fever, imported - USA (NJ) ex Liberia (02)
http://promedmail.org/post/20040930.2700]
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