The Uganda Ebola outbreak — not all negative

The latest epidemic of Ebola haemorrhagic fever, that began on 8 October in the Gulu district of northern Uganda, had, as the Bulletin went to press, claimed 337 victims, with 121 deaths. By mid-November, the outbreak had essentially run its course and WHO epidemiologists considered it under control.

The speed with which this epidemic was snuffed out — in a matter of weeks instead of months — is one feature distinguishing it from most of the eight known previous epidemics. Those outbreaks occurred in Sudan in 1976 and 1979, Gabon in 1994 and 1996 (twice), Côte d’Ivoire in 1994 and Zaire (now the Democratic Republic of the Congo) in 1976 and 1995.

One reason for the rapid outcome, in the view of virologist-epidemiologist Ray Arthur, WHO’s focal point for viral haemorrhagic fevers, was the fact that Uganda very quickly brought WHO into the picture, rather than making a broad appeal for international assistance, as had been the case in previous epidemics. ‘‘As the coordinating body, we could rapidly muster the experts and equipment, and get the logistics going to handle the crisis,’’ Dr Arthur says. WHO also launched an international appeal for funds, to the tune of US$ 848 000, to cope with the outbreak. At this writing, WHO’s partners have given US$ 1.3 million. The team assembled by WHO included experts from the US Centers for Disease Control and Prevention (CDC), Médecins-sans-Frontières & Epicentre, the Italian Istituto Superiore di Sanità, the International Committee of the Red Cross (ICRC), Japan, Germany, and several other institutions. All are part of a global epidemic ‘‘alert-and response’’ network.

A key logistic element that ‘‘really helped get us on top of things’’, according to Dr Arthur, was the setting up, for the first time, of a field lab at the site of the outbreak. The lab could test blood samples on the spot, allowing rapid diagnosis of suspected cases and enabling the team to follow close on the heels of the virus as it spread in the community.’’ And spread it did, not so much from the hospital, Dr Arthur says, which was the main source of ‘‘amplification’’ in several previous epidemics, but rather from funerals. ‘‘The virus was very likely transmitted when people washed cadavers, or simply through close contact during the funeral.’’

The Ugandan epidemic, with about 40% of infected people dying, seems to have been less lethal than previous outbreaks: the case fatality rate in the Sudan outbreaks, with a virus of the same ‘‘Sudan’’ group of strains as in Uganda, was 50–70% and that of the Zaire outbreaks, with a ‘‘Zaire’’ strain, 70–90%. Dr Arthur believes the difference could be related to a more efficient surveillance system picking up cases more quickly and permitting earlier treatment. ‘‘The treatment itself may also have had something to do with it,’’ he says. ‘‘We made a special effort to prevent these patients from dehydrating by giving them oral or intravenous fluid replacement.’’

Not all was plain sailing, though. The presence of civil disturbance in the Gulu area hampered movement of the Ebola team, particularly at night. Some villagers, captured by rebels, can thank the Ebola outbreak for their freedom: the rebels quickly released them when they heard they were from the Gulu area.

Particularly tragic has been the fate of many of the victims of the outbreak who survived the infection. Despite educational messages about the infection and the precautions that survivors should take — avoiding unprotected sex for a few months, for example, since the virus can be found in sperm up to three months after clinical cure — many survivors on returning to their homes were spurned by fearful villagers and found their possessions and dwellings burned to the ground.

Among the unknowns of Ebola haemorrhagic fever is the reservoir of the virus in which it shelters between epidemics. An international team of virologists has for several years been in the Tai Forest, in Côte d’Ivoire, combing the jungle for anything that ‘‘moves, flies or crawls’’, as Dr Arthur puts it — so far to no avail.

Some progress, however, is being made in identifying what may be early warning signs of Ebola outbreaks. WHO and researchers from the US National Aeronautics and Space Administration (NASA), using satellite imaging and rainfall data, have noted a pattern suggesting a link between rainfall after unusually dry weather and the onset of an outbreak. They are currently studying whether the current Uganda outbreak fits this pattern. ‘‘I’d take a bet that this particular epidemic may be just the start of a new cycle of Ebola outbreaks,’’ says Dr Arthur. ‘‘But I hope I’m wrong.’’

John Maurice, Bulletin

World Health Organization Genebra - Genebra - Switzerland
E-mail: bulletin@who.int