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CONTAINMENT AND SURVEILLANCE OF AN EPIDEMIC OF EBOLA VIRUS INFECTION IN YAMBUKU AREA, ZAIRE, 1976

P. SUREAU (1), P. PIOT (2), G . BREMAN (3), F. RUPPOL (4), M. MASAMBA (5), H. BERQUIST (6), D. HEYMANN (3), V. KINTOKI (7), M. KOTH (8), M. MANDIANGU (9), M. MBUYI (7), T. MUYEMBE (7), M. MIATUDILA (10), J.B. MCCORMICK (3), M. NGOY (5), G. RAFFIER (11), N. SAMBU (5), M.K.WHITE (3), S. VAN NIEUWENHOVE (2,4), M. ZAYEMBWA (5)

1. Institut Pasteur, Départment des Virus, Teheran, Iran.
2. Instituut voor Tropische Geneeskunde, Antwerpen, Belgium.
3. Center for Disease Control, Atlanta, U.S.A.
4. FOMETRO, Kinshasa, Zaire.
5 . Sousrégion de la Mongala, Zaire.
6. Karawa, Gemena, Zaire.
7. Cliniques Universitaires, Kinshasa, Zaire.
8. Service d'Hygiène, Kinshasa, Zaire.
9. FONAMES, Kinshasa, Zaire.
10. FOMECO, Kinshasa, Zaire.
11. Mission Médicale Frouegoute, Kinshasa, Zaire.

SUMMARY

Containment measures in the epidemic zone of Yambuku Equatorial Province, Zaire, 1976, included quarantine of the entire Bumba zone and prohibition of all traffic between affected villages. Ebola Virus transmission was interrupted by the closure of Yambuku hospital with cessation of giving injections, by isolation of patients in their villages and by a change in funeral habits. Protective clothing was used efficaciously by high risk individuals such as medical staff.

Surveillance was based on door-to-door surveys by ten locally engaged teams under supervision of an epidemiologist. It covered the whole epidemic zone and a buffer zone. More than 500 villages and more than 30.000 families were investigated. Two physician-led teams investigated the area between Yambuku and Southern Sudan, without finding any case. Logistic support was a major problem throughout the whole campaign.

At the beginning of September 1976, medical staff of Yambuku Mission hospital (consisting of Zairian and Belgian nurses) faced an exceptionally lethal epidemic of an unknown hemorrhagic fever which did not respond at all to any available treatment and which seemed highly contagious. This paper deals with the consecutive measures for containment and surveillance during and after the epidemic in Yambuku area.

FIRST FIELD INVESTIGATIONS

On demand of the medical assistant in charge of the Yambuku hospital, the Chief medical Officer of the Bumba zone arrived in Yambuku on September 15th. he stayed in Yambuku until September 19th making the first accurate clinical and epidemiological study of the new disease and noting the rapid spread of the epidemic along the roads to the villages of the region. His report points out that there was no strict isolation of the patients in Yambuku hospital and that some of the patients escaped to go back and die in their villages where they were buried near the houses and even, sometimes, within the house. No specific containment measures were taken. It was suggested that patients be hospitalized, that burials be made in public cemeteries and that water be boiled before consumption.

Then the news of the death of the Belgian missionary midwife was received on the 19th of September, the Ministry of Health decided to send to the epidemic area a team of two physicians. They arrived in Yambuku on September 23rd when a total of 32 cases had been counted by the missionaries. The report of this second group of investigators evoked the possibility of an atypical yellow fever or of some undetermined arbovirus disease. But, based on the results of the serological tests (Widal), it was eventually concluded that the outbreak was a fulminating epidemic of typhoid fever in a non-vaccinated population". A typhoid vaccination campaign was prescribed for all medical personnel and the population at risk. One acutely ill Belgian nurse and two other missionaries accompanied the team to Kinshasa where they were hospitalized at Ngliema hospital. From a blood specimen of the ill sister, a Marburg-like virus was identified on October 13th.

Meanwhile, the medical staff of Yambuku hospital and the missionaries went on collecting information on the spread of the epidemic with the registration of the number of cases, number of deaths, date of admission at the hospital and date of death. These data, which proved to be very helpful for later investigators, were communicated daily to Kinshasa through the Catholic missions' radio network. When two other missionaries died in Yambuku and the disease apparently irresistibly extended further, a panic arose among the hospital staff and the local population.

Considering this situation, the Ministry of Health decided to send to the affected area a second epidemiological mission. This team arrived in Bumba on October 4th 1976, where in cooperation with the local medical and administrative authorities, it was decided to establish severe quarantine measures to protect the town of Bumba (50.000 inhabitants) which is an important port on the Zaire river and a very busy commercial centre. The entire Bumba zone was quarantined and all traffic between the city and the rest of the country prohibited by the use of army controlled roadblocks. In Bumba two quarantine camps were established ; near the hospital, one building was reserved for the isolation of 43 students and their contacts evacuated from Yambuku high school and a military camp was evacuated for the isolation of possible patients and contacts. Two active cases, who had fled from Yambuku, were strictly isolated in a house and, immediately after death on October 6th, buried by team members wearing protective clothing. Furthermore, health education sessions were organized in different parts of Bumba. When the team reached Yambuku on October 6th, the hospital had closed down; all patients had left, disseminating the disease in villages as far away as 50 km from the mission. Individual protective material, consisting of gowns, gloves and masks, and disinfectants were distributed to the medical staff and the principles of barrier nursing explained. Strict isolation of patients and affected villages was recommended, together with the establishment of roadblocks on the ways to Yambuku and Yandongi.

This team noted the predominant role of the hospital in the dissemination of the disease and the explosive character of the outbreak, suggesting that several Contaminations had occurred simultaneously. Yellow fever or typhoid were discarded and the possibility of Lassa fever was evoked. Early after their return to Kinshasa on October 9th, the virus responsible for the outbreak was identified.

FURTHER INVESTIGATIONS AND SURVEILLANCE BY THE INTERNATIONAL MEDICAL COMMISSION (IMC)

An International Medical Commission was formed on October 18th, 1976, under the direction of the Minister of Health of Zaire to confront the outbreak which, according to the reports received from the affected area, was reaching about 270 cases by the middle of October. For the first time, one and a half months after the beginning of the epidemic, enough resources in man-power, equipment and organization were put together to fight the disease. Equipment for individual protection and the performance of strict barrier nursing was, at last, available in adequate quantity.

First field investigations by the IMC.

A subgroup of the commission, composed of 6 physicians, left Kinshasa for Bumba by air on October 19th. A landrover was transported with them in a C-130 of the Zairian Air Force, together with protective material and dry ice for preserving specimens for virological or serological investigation. The objectives of this short-term investigation were :

1. Determination of the geographical extension of the epidemic, the actual acti vity of the outbreak and institution of measures designed to interrupt the epidemic chain.

2. Identification of survivors of the infection and evaluation of the possibili ty to immune plasma collection from them.

3. Evaluation of the necessity and logistic needs for the installation of a treatment and investigation base in the epidemic area.

In Bumba, control measures were discussed with medical and administrative authorities. Collective containment consisted in the establishment or reinforcement of road blocks on roads leading in and out of all villages in the Bumba zone. The entire infected zone was placed in quarantine until 6 weeks after the death of the last case. All traffic to and from Bumba by air, road, railway and the Zaire river was suppressed, and all passengers and cargo transportation along the roads from Yambuku was prohibited. Military and local authorities were in charge of these road blocks. A one-day survey by road was then conducted by 4 subteams to determine the importance of the outbreak in number of cases, both past and active, the number of affected villages, the geographic spread of the epidemic and to look for possible convalescents. A brief stop of about 15 minutes was made in every village, where local authorities were asked for number of cases and deaths, date of first and last death in the village and the presence of active cases. If active cases were present, at least one patient was seen and questioned by the epidemiologist but without having close contact. Clinical features were noted. All data were registered on forms made by team members using standardized definitions (see addendum) . 69 villages within a perimeter of about 50 km around Yambuku were visited. Apparently the outbreak was, at the time of this survey, diminishing. One subteam investigated the neighbouring villages near Yambuku and Yandongi where, according to the missionaries' reports, most victims had occurred. The 2 physicians of this team were protected by disposable gowns, gloves, surgical paper masks, hoods, plastic bags serving as boots and motor-cycle goggles when examining patients. All protective clothing, except the goggles, was burned on the spot, immediately after each examination. This subteam took blood samples for virus isolation of 9 active cases, 5 of whom died within the following days, and identified 5 possible and 1 confirmed convalescents from whom serum specimens were obtained.

After a crude check of their haemoglobinemia (Tallquist method and Unopet), two convalescents were convinced to accompany the team to Kinshasa to become the first donors of hyperimmune plasma,

Some days later, a Zairian Air Force helicopter was available for visiting remote areas from which no direct information was gathered by the missionary surveillance system. In this way, the epidemic zone could be correctly delineated.

Methods recommended for disease control included rapid burial of cadavers with their clothing impregnated in sodiumhypochlorite or formalin, together with all potentially infectious items. The mourning ceremonies were to be limited and all direct contact with the cadaver or excreta be avoided. Houses were to be disinfected if disinfectants available, and in several cases huts were burnt down by the population. The mission hospital was disinfected by fumigation with formaldehyde, matrasses removed and burnt or left in the sun for several days. Floors and walls were scrubbed and disinfected. Furniture and all items were left in the sun for disinfection.

Logistic support was a major problem throughout the whole operation in the Bumba zone, especially during the preliminary surveys described above. Communication between Yambuku, Bumba and the commission in Kinshasa was provided only through the catholic missions network. Considerable delays occurred and many radio messages to Kinshasa were badly received, or not at all. The field-team did not get any message from the IMC in Kinshasa and demands for air transport back to Kinshasa were left unanswered, causing difficulties in preserving the specimens for virus isolation at appropriate temperature because of a very limited stock of dry ice. Local transport by road was often problematic because of the rainy season and the IMC-team, owning only one landrover, depended on vehicles provided by the catholic missions of Bumba and Yambuku. Moreover, there was a general shortage of fuel in the area. Suitable accommodation in Bumba and Yambuku was provided through the kindness of the local catholic missions.

The Commission's survey in North eastern Zaire (figure 1).

Two physician-led teams, with vehicles, were flown to north-eastern Zaire on November 1st to find a link between the epidemics in the Sudan and in Yambuku. Visits were made to health units, cities and villages; interrogations were made regarding outbreaks of severe hemorrhagic disease during the previous 9 months. They did not find either isolated cases nor foci of hemorrhagic fever in the area nor along the Sudan and Central African Empire border during a two-week search. Although no recent or past cases were found, one of the epidemiologists observed regular traffic between Southern and Haut-Zaire and the Bumba zone which can be reached in four days from Nzara (Sudan), where a similar outbreak started in July.

Figure 1 : Itineraries of two survey teams in Haut Zaire

The organized surveillance programme.

Following the preliminary survey of the International Commission, the setting up of containment and surveillance in the epidemic zone around Yambuku and in a buffer zone about 20 kms around this area was given top priority.

The programme was based on the following principles :

1. Intensive search of active cases by door-to-door surveys in each village in the affected area.

2. Organization and reinforcement of containment measures in the villages.

3. Appropriate health education.

4. Detection of possible convalescent cases of disease.

At the beginning of November, two main bases with modern radio equipment, fuel and food depots and lodgment facilities were established at Yambuku and Ebonda, a village on the Zaire river 12 km west of Bumba. There were three peripheral bases with fuel depots, supplied by helicopter, at Abumombazi, Tshimbi and Yalosemba. An Air Force helicopter was available in Bumba for transport of goods and supervision of the peripheral bases and diesel stocks.

Ten teams were formed, eight of them were put at the disposition of the IMC by several organizations ( State owned and catholic and protestant mission hospitals , the National Campaign for the Eradication of Smallpox, the National Campaign against Sleeping Sickness, PL2 Plantation Company), and two teams were recruted at Bumba. Each team was composed of a paramedically trained teamleader, an auxiliary and a driver - all living in the Equatorial Province of Zaire. In total, 38 persons participated in the campaign. Each team was issued with the following protective clothing for 50 examinations (masks, gloves, boots, gowns, hoods, goggles and respirators); forms, clipboards, pens and paper; geographical maps; basic camping material (mosquito nets, oil lamps, torches, blankets, sheets, water containers, cooking equipment); food (C-rations); disinfectant (sodiumhypochlorite); basic medication to treat villagers (aspirin, chloroquine, tetracyclin, antidiarrheal) first-aid kit for team members.

All the teams took part in a day of training in Ebola hemorrhagic fever and investigation technique. A basic instruction document, including standardized data collection forms, was given to each participant. The training programme covered general information on the epidemic, differential diagnosis of the disease, instructions for personal protection, the principles of isolation and quarantine and a discussion on the themes for action in sanitary education. An epidemiologist directed the teams' first day in a village to elucidate investigation techniques.

At the first visit to the village, the population was assembled around the village chief and the reason for the visit and current state of the epidemic was explained. The accent was then put on isolation and quarantine measures, should cases occur. Many teams went further and explained the dangers of infections and advised the construction of isolation huts.

During a subsequent house to house survey the name of the family head and the number of persons in each family were recorded. Data on past cases were collected. Suspect cases were not examined. Medicines were given to them and arrangements were made for isolation in the village. Work reviews were held daily at Yambuku and Ebonda and physicians were sent to follow up on suspect cases and to bleed candidate convalescent cases. Every village was visited a second time in much the same way as the first visit, with the accent on the control of fever cases. A third rapid survey was made in which village chiefs were asked whether any new suspect cases had occurred.

The covered area and the circuits of the teams are traced on figure 1; 550 villages and 34,000 families or approximately 170,000 persons have been visited by the surveillance teams. The last active case was found to have died on November 5th 1976 in Bongolu, 38 km east from Yambuku. Several cases of febrile illness were found by the teams and all responded to antimalarial treatment.

Based on these facts, and continuing the surveillance for another 4 weeks, the lifting of quarantine on 16 December 1976 was advised, that is, six weeks after the date of the last death. The Yambuku Hospital was reopened around mid-November.

Under supervision of an epidemiologist, passive surveillance was continued in the epidemic area till the end of January when the plasmaphoresis programme was stopped. Village leaders were regularly asked for suspect cases and the hospital records were daily controlled by a physician of the IMC. Much emphasis was put on limitation of injections and on the proper way to sterilize syringes and needles and on the maintenance of sterility.

On February 2nd 1977, the death of a suspect case of hemorrhagic fever was reported at Yambuku hospital which caused much concern among hospital staff and population. The patient was isolated, nursed and buried by convalescents from the epidemic according to the instructions issued by the IMC, but, unfortunately, no specimens were taken for virus isolation. Subsequent investigations by an IMC epidemiologist, who arrived in the area one week after the patient's death, did not reveal any additional cases but were inconclusive as to the etiology of the disease.


DISCUSSION

Containment measures in the epidemic zone of Yambuku consisted mainly in closure of Yambuku mission hospital, strategic isolation of patients and villages and protection of high risk individuals with special equipment and information.

The isolation of villages and the prohibition of all traffic between the villages by roadblocks proved to be very efficient and were surprisingly well respected by the population. These measures certainly prevented further spread to unaffected villages which were particularly vigilant when there were cases in adjacent villages. Many elder people remembered containment measures as dictated during past smallpox epidemics and made them apply. At the end of the epidemic isolation of patients was more or less practised in the villages and, occasionally, burials were performed soon after death without preparing the cadavre (washing, touching, dressing, vigil) but this, especially the last, was very hard to accept for the family. In some instances, huts of the deceased were burnt down. It is nearly impossible to evaluate the impact of these measures.

Protective clothing, mentioned earlier, was worn systematically by investigators during contact with suspect cases. Team-members safely examined several

virologically confirmed patients with this equipment, including disposable surgical masks, respirators not being available at that time. At the moment, information on virus shedding is very limited and thus far, virus has only been isolated from the blood and seminal fluid 1. There is an urgent need for virological studies on the presence of Ebola virus in different sites of the body, in order to introduce rational containment measures.

It was shown that a rapid organization of systematic active surveillance is possible, even in areas with limited resources in skilled manpower and technology, providing basic logistic problems are resolved. Transportation was a major requirement during the whole campaign, and lack of vehicles and fuel was the main obstacle at the beginning of the activities.

Very valuable use was made of existing health service facilities such as mobile teams of the Smallpox eradication campaign, the sleeping sickness control programme, and students from a paramedical school. Only active surveillance can inform authorities with serious data on the status of the outbreak and when to lift quarantine which should not be ended until at least twice the incubation time has passed since the last case has occurred.

It is recommended that countries at risk for highly mortal hemorrhagic diseases have an efficient surveillance system and minimum equipment for sample collection and shipment to high security laboratories. International collaboration appears to be necessary for containment of such outbreaks.

REFERENCES
1. Emond, R.T.D., et al. (1977) A case of Ebola Virus Infection. Brit. Med. J., 2, 541-544.
ADDENDUM
DEFINITIONS USED DURING FIELD INVESTIGATIONS IN THE EPIDEMIC AREA OF YAMBUKU

a) PROVEN CASE : patient manifesting an acute clinical syndrome and in whom the virus had been isolated and/or had specific antibodies.

b) PROBABLE CASE : person having had three days of headache, backache, fever,abdominal pain, nausea and/or vomiting, as well as hemorrhage, with no other diagnosis and not responding to treatment. It is essential that there should have been a contact with another case of Ebola virus infection or a history of injection.

c) POSSIBLE CASE : patient with at least 24 hours of fever and headache, with no other diagnosis and not responding to treatment, having had a contact with a probable or proven case during the previous three weeks or a history of injection.

CONTACT : a person having had direct face-to-face contact with a), b) or c), that is, having slept in the same room, having taken meals together and having cared for a patient or prepared the body, either two days before the beginning of symptoms, during illness or immediately after death.

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