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Update: Outbreak of Ebola Viral Hemorrhagic Fever -- Zaire, 1995
As of June 25, public health authorities have identified 296
persons with viral hemorrhagic fever (VHF) attributable to
documented or suspected Ebola virus infection in an outbreak in the
city of Kikwit and the surrounding Bandundu region of Zaire (1,2);
79% of the cases have been fatal, and 90 (32%) of 283 cases in
persons for whom occupation was known occurred in health-care
workers. This report summarizes characteristics of persons with VHF
from an initial description of cases and preliminary findings of an
assessment of risk factors for transmission.
A case was defined as confirmed or suspected VHF in a resident
of Kikwit or the surrounding Bandundu region identified since
January 1. The median age of persons with VHF was 37 years (range:
1 month-71 years); 52% were female. Based on preliminary analysis
of 66 cases for which data were available, the most frequent
symptoms at onset were fever (94%), diarrhea (80%), and severe
weakness (74%); other symptoms included dysphagia (41%) and hiccups
(15%). Clinical signs of bleeding occurred in 38% of cases.
Potential risk factors for intrafamilial transmission were
evaluated for secondary cases within households of 27 primary
household cases identified through May 10. A primary household case
was defined as the first case of VHF in a household; household was
defined as persons who shared a cooking fire at the onset of
illness in the primary household case. Among 173 household members
of the 27 primary household cases, there were 28 (16%) secondary
case-patients. The risk for developing VHF was higher for spouses
of the primary household case-patients than for other household
members (10 {45%} of 22 compared with 18 {14%} of 151; rate ratio
{RR}=3.8; 95% confidence interval {CI}=2.0-7.2) and for adults
(aged greater than or equal to 18 years) than for children (24
{30%} of 81 compared with four {4%} of 92; RR=6.7; 95%
CI=2.4-18.4).
Needle sticks or surgical procedures during the 2 weeks before
illness were reported for two of the 27 primary household
case-patients and none of 28 secondary case-patients. Of the 28
secondary case-patients, 12 had direct contact with blood, vomitus,
or stool of the ill person during hospitalization (i.e., later
stages of illness), and 17 simultaneously shared the same hospital
bed. Of 78 household members who had no direct physical contact
with the person with the primary household case-patient during
their clinical illness, none developed VHF (95% CI=0-4).
Reported by: M Musong, MD, Minister of Health, Kinshasa; T Muyembe,
MD, Univ of Kinshasa; Technical and Scientific International
Coordinating Committee for Viral Hemorrhagic Fever, Kikwit, Zaire.
World Health Organization Kinshasa, Zaire. World Health
Organization, Brazzaville, Congo. World Health Organization,
Geneva, Switzerland. Medecins Sans Frontieres, Belgium. Epicentre,
Paris, France. Prince Leopold Institute of Tropical Medicine and
Hygiene, Antwerp, Belgium. Div of Viral and Rickettsial Diseases,
National Center for Infectious Diseases; International Health
Program Office; Epidemiology Program Office, CDC. Editorial Note
Editorial Note: The incidence of VHF related to Ebola virus in
Kikwit has diminished following the institution of interventions
including 1) training of medical and relief personnel on the proper
use of protective equipment, 2) initiation of aggressive
case-finding; and 3) educational measures in the community (e.g.,
pamphlets and public announcements) (1,2). However, cases continue
to occur, and each case has the potential to be a source for
additional infections. Therefore, ongoing measures including
continued intensive surveillance, training activities, and public
education are necessary to contain the epidemic.
To maximize prevention and control measures, prompt laboratory
diagnosis is an important component of surveillance. An
enzyme-linked immunosorbent assay (ELISA) detected Ebola antigen in
specimens initially submitted to CDC from 11 of 13 acutely infected
persons (1). Ongoing testing of additional specimens will assess
the utility of this ELISA as a rapid diagnostic test that could be
used locally. In addition, Ebola antigen was detected in multiple
formalin-fixed tissue samples (liver, lung, and skin) of seven
case-patients by immunohistochemical (IHC) staining using a
specific polyclonal antibody. These findings suggest that IHC
staining of fixed tissue may assist in surveillance for hemorrhagic
fevers in Africa and other countries. Other activities include
ecologic studies to identify the natural reservoir of the virus;
these studies are focusing especially on mammals, nonmammalian
vertebrates, and arthropods.
Transmission associated with health-care providers and
caregivers has been a prominent feature of the current and previous
VHF outbreaks in Africa attributable to Lassa, Marburg, Ebola, or
Crimean-Congo hemorrhagic fever viruses (3). In some outbreaks,
transmission from patient to patient within hospitals has been
associated with the reuse of unsterile needles and syringes. As in
previous outbreaks, high rates of transmission in this outbreak
have occurred from patients to health-care workers and to family
members who provided nursing care without appropriate barrier
precautions to prevent exposure to blood, other body fluids,
vomitus, urine, and stool. Based on findings in this report, the
risk for transmitting infection from patients appears to be highest
during the later stages of illness, which is characterized by
vomiting, diarrhea, shock, and often hemorrhage. However, a small
number of cases of VHF in Zaire have been reported in family
members whose only contact with an infected person was in the
domestic setting within a few days after onset of illness.
Updated recommendations for the management of VHFs
attributable to these viruses in the United States are presented in
a Notice to Readers in this issue (4).
References
CDC. Outbreak of Ebola viral hemorrhagic fever -- Zaire, 1995.
MMWR 1995;44:381-2.
CDC. Update: outbreak of Ebola viral hemorrhagic fever -- Zaire,
1995. MMWR 1995;44:399.
CDC. Management of patients with suspected viral hemorrhagic
fever. MMWR 1988;37(no. S-3):1-15.
CDC. Update: management of patients with suspected viral
hemorrhagic fever -- United States. MMWR 1995;44:475-79.
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