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Ebola Outbreak in Congo

By Luciana Borio, M.D., May 31, 2005

On May 18, the WHO reported that an outbreak of Ebola hemorrhagic fever was confirmed in the Republic of the Congo. The outbreak was apparently initiated by a family of hunters who contracted the disease after finding the body of a dead chimpanzee that they took home to eat. As of May 23, a total of 11 cases had been reported, including 9 deaths, and approximately 80 contacts were placed under surveillance for the development of symptoms. The outbreak was reported to be under control after the implementation of swift infection control measures by local public health authorities. However, in 2003, approximately 150 people died from Ebola in the same area.

Ebola virus was first identified in 1976 after outbreaks of acute hemorrhagic fever occurred in Sudan and Zaire (now Republic of the Congo). Ebola virus belongs to the Filoviridae family (which also includes the Marburg virus). There are four distinct subtypes of Ebola virus: Zaire, Sudan, Cote d’Ivoire, and Reston. The latter is not known to cause human illness. Case-fatality rates range from 50-90% in clinically ill persons, depending on the subtype.

This is significant because along with a number of other “hemorrhagic fever viruses,” Ebola is considered a Category A agent. However, there has never been a case of Ebola disease imported into the United States during outbreaks in Africa. This may be in part due to the fact that transmission of disease does not appear to occur prior to the development of symptoms.

Additional information:
WHO’s Ebola hemorrhagic fever fact sheet number 103
CDC’s fact sheet on Ebola hemorrhagic fever
Hemorrhagic fever viruses as biological weapons

WHO: Pandemic Influenza Risk Increases

By Eric Toner, M.D.

This week, the WHO underscored the imminent threat posed by the current H5N1 outbreak in Southeast Asia. Speaking at the WHA, both Dr. Lee Jong-wook, Director-General of the WHO and U.S. Secretary of HHS, Mike Leavitt expressed dire concern about avian influenza, describing it as “the most serious health threat facing the world today” and an “urgent health challenge.”

On May 6-7, an urgent expert consultation meeting was held in Manila in response to new information indicating that “the epidemiology of H5N1 could be changing . . . and the risk for pandemic influenza could have risen.” The expert panel noted specifically that in northern Viet Nam in the last 5 months:

  • There has been an increase in the number of clusters of cases in the north (8) as compared to the south (2).

  • The interval between the first and last cases in clusters in the north have prolonged, which is inconsistent with a discreet common source exposure.

  • The case fatality rate in the north has decreased.

  • Sub-clinical infections have been observed.

  • The age range of victims has expanded.

Although careful to say that this has not been proven, the expert group concluded that this pattern is consistent with human-to-human transmission and that the recently emerging H5N1 viruses are more infectious for humans. The implication is that the virus may be adapting to a human host, causing less mortality, infecting a greater range of people, and being spread person to person.

In addition partial neuraminidase inhibitor resistance has been detected in one viral specimen. Neuraminidase inhibitors are the only antiviral drugs to which the current strain of H5N1 is sensitive.

Finally, the group of experts commented on the lack of relevant surveillance information, the lack of antigenic and genetic information sharing, and the urgent need for countries and individual researchers to release information that has already been collected on the H5N1 viruses. As we have pointed out in previous articles, inadequate surveillance of the current outbreak undermines all other attempts at preparedness.