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New Arenavirus Identified as Cause of Cluster of Illness, Death in South Africa and Zambia

By Amesh A. Adalja, M.D., November 7, 2008

Through molecular diagnostic techniques, a previously unknown arenavirus has been identified as the etiologic agent responsible for 4 deaths in Africa that occurred in September and October of 2008.1

Second New Disease Causing Arenavirus this Year

Identified utilizing genetic sequencing, investigators from the Communicable Diseases Laboratory in South Africa, the U.S. Centers for Disease Control and Prevention (CDC), and Columbia University discovered that the virus is an “Old World” arenavirus, with similarities to Lassa fever virus.1,3 This marks the second new arenavirus identified as a disease-causing agent in the past year; the first was identified after several transplant patients were killed by the “Dandenong” virus as reported in the New England Journal of Medicine in March 2008. The earlier outbreak was investigated using similar methods.2,4

Clinical Characteristics and Laboratory Features

To date, there have been 5 case patients and 4 fatalities, with clinical characteristics that include a flu-like illness with increasing severity over 7 days, pharyngitis, diarrhea, and rash. Upon hospitalization, some clinical improvement was observed, but it was followed by a rapid decline culminating in respiratory failure and shock. The incubation period of this virus has been estimated at 7 to 13 days, with death occurring 9 to 12 days after illness.3

Although arenaviruses often cause hemorrhagic fevers, bleeding has not been a prominent feature of these cases; nonetheless, full VHF precautions were implemented.

Laboratory features included thrombocytopenia, elevated liver transaminases, and variable presence of leukopenia followed by leukocytosis. Patients were treated with ribavirin based on its efficacy in treating Lassa fever.3

Cases Restricted to Close Contacts

Cases have been restricted to close contacts of infected patients. The index case was a safari booking agent in Zambia who spread the infection to a paramedic, a nurse, and a hospital housekeeper, all of whom participated in the patient’s care. The only patient who did not succumb was the 5th and final case—a nurse who cared for one of the secondary victims. Contact tracing, investigation of the index patient, and serologic studies searching for asymptomatic infection are currently underway.3

Arenaviruses are divided into Old World (Lassa fever and Lymphocytic Choriomeningitis Virus) and New World (Junin, Machupo, Guanarito, Sabia viruses) groupings. They have long been known to cause human disease in those exposed to rodent urine and droppings.3,4 They are classified as Category A biological agents because of their ability to cause severe human illness and to be disseminated as an aerosol. The two recently discovered additions to this family of viruses are presumed to be the result of zoonoses. These cases illustrate the ongoing threat of emerging infections and the power of modern molecular diagnostic techniques to ascertain the identity of the responsible agent. This virus adds to the growing list of lethal infectious pathogens with the potential to be exploited as weapons in the future.

References

  1. World Health Organization. New virus from Arenaviridae family in South Africa and Zambia – Update. October 13, 2008. http://www.who.int/csr/don/2008_10_13/en/index.html. Accessed November 6, 2008.

  2. Palacios G, Druce J, Du L, et al. A New Arenavirus in a cluster of fatal transplant-associated diseases. N Engl J Med. 2008; 358:991-998. http://content.nejm.org/cgi/content/
    short/358/10/991
    . Accessed November 6, 2008.

  3. National Institute for Communicable Diseases. Arenavirus outbreak, South Africa. Communicable Diseases Communiqué. 2008;7:1-3. http://www.nicd.ac.za/pubs/communique/2008/
    NICDCommOct08Vol07_10.pdf
    .  Accessed November 6, 2008.  

  4. Charrel RN, de Lamballerie X, Emonet S. Phylogeny of the genus Arenavirus. Curr Op Micro. 2008;11:362-368.