Another case of Viral Haemorrhagic...

The mystery viral haemorrhagic fever which killed three people in South Africa has been provisionally identified as an arenavirus, the National Institute for Communicable Diseases and the Department of Health said on Sunday.
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Arenaviruses cause chronic infections in multimammate mice — a kind of wild mouse — who excrete the virus in their urine which can then contaminate human food or house dust.

Viruses similar to the Lassa fever virus has been found in rodents in Africa, but other than in West Africa have not been found to cause diseases in humans.

She said there was no indication that arenaviruses which could cause disease in humans were present in South African rodents.

Blumberg said further tests still needed to be done

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tomatosarefruit said:

Just heard it on e news... found a link on IOL

http://news.iafrica.com/sa/1045302.htm

In my mind this is a real worry as it is spread by vermin among other things... hope they're right about our local population not being contaminated...
but I wonder where it came from?

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Arenaviruses are emerging in the Americas and Africa and can cause hemorrhagic fevers with case fatalities of up to 15%. These viruses are mainly transmitted through contact with the excreta of their natural hosts, rodents of the family Muridae. The Old World arenavirus Lassa virus causes up to 300,000 cases of Lassa fever annually in endemic foci of 2 geographically disjunct regions of West Africa (1).

Most arenaviruses have been associated with 1 specific reservoir host species (2). Knowledge of the geographic distribution of the taxonomically defined host is therefore essential to understand the epidemiology of human infections. In the 1970s, the rodent host of Lassa virus was classified as Mastomys natalensis (3); later, when hemoglobin electrophoresis was used for species determination, M. erythroleucus and possibly M. huberti were also proposed as hosts (1). In addition, Lassa virus antigen was detected in Rattus and Mus genera, raising the possibility that other rodent genera could be involved in transmission (4).

The taxonomy of Mastomys is considered unresolved, and species determination remains problematic; 8 distinct species are recognized, and several coexist in Lassa fever–endemic areas (5). The uncertainty about their precise natural host relationships with Lassa virus is considered a major obstacle for a better understanding of the restricted distribution of Lassa fever in West Africa (6).

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LASSA FEVER: ARENAVIRAL DISEASES
Lassa fever is caused by a virus transmitted from asymptomatically infected rodents to humans (6). Most infections are mild, but some are severe, causing a hemorrhagic fever that is often fatal. The virus, a member of the virus family Arenaviridae, is a single-stranded RNA virus. Arenaviruses are transmitted by rodent hosts (with the exception of Tacaribe virus, which has been isolated from bats) and can be divided into two groups: the New World or Tacaribe complex and the Old World or lymphocytic choriomeningitis virus (LCMV)/Lassa complex. Viruses causing human illness are Lassa virus (Lassa fever), Junin virus (Argentine hemorrhagic fever), Machupo virus (Bolivian hemorrhagic fever), Guanarito virus (Venezuelan hemorrhagic fever) (7), Sabia virus (Brazilian hemorrhagic fever), LCMV (meningitis, encephalitis, meningo-encephalitis, congenital fetal infection with neurological sequelae, fever, coagulopathy, and multi-organ failure and death in immunosuppressed organ recipients), and Flexal virus (an influenza-like illness that has caused deaths among laboratory personnel handling infected rodents in Brazil) (1).

Each virus is associated with one or more closely related rodent species that constitute its natural reservoir. Tacaribe complex viruses are generally associated with the New World rats and mice (family Muridae, subfamily Sigmodontinae). The LCM/Lassa complex viruses are associated with the Old World rats and mice (family Muridae, subfamily Murinae). Taken together, these types of rodents are located across most of the earth’s land mass, including Europe, Asia, Africa, and the Americas, although the individual viruses (with the exception of LCMV) are restricted to limited geographic areas.

Lassa fever is limited to rural areas of West Africa, with areas of hyperendemicity in eastern Sierra Leone, Guinea, Liberia, and Nigeria (6). Peridomestic exposure to infected rodents is the most likely source of human infection. Transmission of arenaviruses to humans can occur via inhalation of primary aerosols from rodent urine, by ingestion of rodent-contaminated food, or by direct contact of broken skin with rodent excreta (1,6). Rodent infestation facilitated by inappropriate food storage increases the risk of human infection. Person-to-person spread of Lassa and Machupo viruses has also been described, most notably by large droplet and contact transmission in the hospital setting. Despite one anecdotal report of possible airborne transmission, this mode is not believed to be an important route of infection from person to person. Laboratory handling of infectious specimens and contact with contaminated medical equipment are also associated with transmission.

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The Aeromedical Isolation Team
The purpose of the isolation team is to safely transport patients with potentially lethal communicable diseases for which no effective vaccines, chemoprophylaxis, or specific therapies exist. These would include patients with an unknown disease pending identification of the pathogen, patients with viral hemorrhagic fevers (notably those due to filoviruses and arenaviruses), and those suspected of being affected by a biological attack (Table 1) (3). Etiologic diagnosis and medical care would be provided at USAMRIID.

Table 1. Infections and conditions requiring containment care during transport


Arenavirus infection
Argentine hemorrhagic fever (Junin virus)
Bolivian hemorrhagic fever (Machupo virus)
Brazilian hemorrhagic fever (Sabi� virus)
Lassa fever
Venezuelan hemorrhagic fever (Guanarito virus)

Bunyavirus infection
Congo-Crimean hemorrhagic fever
Filovirus infection
Ebola
Marburg
Orthopoxvirus infection
Monkeypox
Variola
Pneumonic plague until sputum cultures are negative
Any unknown virulent communicable disease pending diagnosis
Suspected biological–warfare—caused infection

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USAMRIID can simultaneously deploy two teams, each consisting of one physician, one registered nurse, and four to six medics. Each team can transport and manage one patient. In addition, the team can deploy a portable containment laboratory with rapid diagnostic assays, including enzyme-linked immunosorbent assays and polymerase chain reaction (PCR), as well as standard clinical laboratory support, for all agents listed in Table 1 (in development: Machupo, Sabi�, and Guanarito viruses).

Deployable on rotary and fixed-wing military aircraft, the team conducts in-flight training and can deploy within 6 to 12 hours of notification. Although a military asset, the team has been mobilized for situations involving civilians. Requests may be forwarded through local and state health departments to the Centers for Disease Control and Prevention, through the Federal Emergency Management Agency, or through the Federal Bureau of Investigation and are then reviewed by the Directorate of Military Support. Evacuation of non-U.S. citizens from other countries to the United States would require coordination through the Department of State, Bureau of Political-Military Affairs.

Biosafety Containment under Field Conditions
Maximum biological containment is designed to prevent transmission of highly hazardous pathogens and is accomplished in two steps. First, the health-care worker wears an impermeable suit consisting of a lightweight polyvinyl chloride (PVC) coverall, a separate hood, and vinyl boots (Figure 1). A HEPA-filtered respirator powered by a rechargeable battery supplies air under positive pressure for breathing and cooling. HEPA filters are certified to remove 99.7% of particles 0.03 �m to 3.0 �m diameter; each filter is tested with particulate aerosol challenge studies before delivery. Air enters at a rate of 170 L/min through an intake port near the top of the hood and exits through an exhaust valve at its base. Two-way radios permit communication between team members and patients. The suit and respirator ensemble has been tested by the manufacturer by particulate aerosol challenge and meets the standards of the National Institute of Occupational Safety and Health and the Occupational Safety and Health Administration for working in environments with respiratory hazards.


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Figure 1: Aeromedical isolation team members in field-protective suits equipped with battery-powered HEPA-filtered respirators transporting the stretcher isolator, a light-weight unit designed for initial patient retrieval. The team trains on several types of military aircraft, including the C-130 transport shown in the background.
Second, the patient is isolated within a sealed container under negative air pressure maintained by a battery-powered HEPA-filtered ventilation system providing five air exchanges per hour (Figure 1). Two isolators are used: the stretcher isolator, a lightweight unit for initial patient retrieval (Figure 1), and the Vickers aircraft transport isolator (VATI), a larger unit for definitive transport and in-flight care (Figure 2; Table 2).

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Pooky said:

This was posted a while back I think.

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Syndre said:

Wasn't it brought in from Zambia?

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tomatosarefruit said:

This is yesterday's news - i.e. fresh...
Yes, but I meant where was it's source - what was the carrier. If it's lasser fever which is primarily carried by infected vermin in West Africa - and the article says that our local vermin are not at risk... so the question is, how did it get here?

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PeterCH said:

At this stage this is unknown, hopefully Zambian mice haven't picked it up
from their north-western counterparts.

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