The world's last endemic case of smallpox: surveillance and containment measures

Bulletin of the World Health Organization, 58 (2): 279-283 (1980) The world's last endemic case of smallpox: surveillance and containment measures* A. DERIA,1 Z. JEZEK,2 K. MARKVART,3 P. CARRASCO,3 & J. WEISFELD 3 On 31 October 1977, the world's last known case ofendemicsmallpox was discovered in Merca, Somalia. The source ofinfection was quickly identified; 19 dayspreviously, the male patient had been in contact with two other cases for not more than 15 minutes, but the surveillance activities surrounding these cases did not identify him as a contact. Thepatient was isolated and containment and surveillance activities and a vaccination campaign were rapidly instituted; 161 contacts were identified, 41 ofwhom had not been vaccinated within the last three years. The patient recovered andfortunately no other cases occurred. In 1967, whenWHO commenced its intensified pro- gramme to eradicate smallpox throughout the world, 46 countries reported cases of the disease and it was considered endemic in 33 of these. Almost 132 000 cases were reported in that year, but these certainly represented only a fraction of those that actually occurred. By 1977 the programme had succeeded in interrupt- ing smallpox transmission in all countries except Somalia in north-east Africa. Endemic smallpox had become re-established there in 1976 following multiple importations of the disease from Ethiopia. No cases were detected in Ethiopia after August 1976, but the disease persisted in Somalia despite efforts by the government and WHO to interrupt transmission. By the end of the year it was thought that these efforts had succeeded. However, increased surveillance in mid- March 1977 revealed widespread outbreaks through- out southern Somalia and in May 1977 the govern- ment declared the situation to be an emergency. The I National Programme Manager, Smallpox Eradication Programme, Mogadishu, Somalia. 2 Medical Officer, Smallpox Eradication, World Health Organ- ization, 1211 Geneva 27, Switzerland. 3 WHO Consultant, Smallpox Eradication Programme, Mogadishu, Somalia. peak of the epidemic occurred in late June, at which time more than 3000 national staff and 24 inter- national epidemiologists were involved in contain- ment activities. In all, 3228 smallpox cases were detected in ten regions in the south of Somalia and one imported case occurred in the northern part of the country. These cases occurred in 947 localities. By October smallpox transmission persisted in only four southern regions of the country, the last to experience cases being Lower Shabelli Region. What proved to be the last outbreak, occurred at the end of October 1977. On 31 October, an urgent telephone call from the WHO epidemiologist in Lower Shabelli Region in- formed the smallpox eradication headquarters in Mogadishu of a smallpox case in the town of Merca (Fig. 1). Merca is a busy regional centre and international port with a population of about 30 000. It is only two hours drive by surfaced road from the capital, Mogadishu, and is connected by bus services with the six other towns in the region. Most of the inhabitants are employed in local light industry or at the port. Administratively, the town is divided into three wards, each having four branches with 200-400 houses. The case was detected in Horseed Ward which forms the south-western sector of the town. 3945 -279- A. DERIA ET AL. Fig. 1. Location of Merca. /+ 0 25 50 75 100 km Scale Xaargarsal area Legend )Dugu lie Roads Localities Movement of affected nomadic community e after detection before detection _ Movement of smallpox cases from Kurtunwarey * Outbreak localities i3 Isolation camp WHO 78457 Fig. 2. Movements of the smallpox-affected nomadic community in Lower Shabelli region, 15 August - 18 October1977. co0 280 WORLD'S LAST ENDEMIC CASE OF SMALLPOX Epidemiological investigations The patient, Ali Maow Maalin, a 23-year-old cook at Merca Hospital, had not been previously vaccinated against smallpox and when discovered was suffering from moderately severe, clinically typical smallpox. Investigation revealed the following sequence of events: 22 October: The patient developed a fever while at work and went home. 23-24 October: At home he was visited by many friends, including neighbours and hospital employees. 25 October: Admitted to the medical ward of Merca Hospital with a diagnosis of malaria, he was treated accordingly. He was visited by many friends and hospital employees and walked through the hospital and outside the compound to receive his salary and visit a friend. 26 October: A rash developed in the evening. 27 October: The patient was discharged after an attending physician had made a provisional diag- nosis of chickenpox. 28 October: At home, very ill, he was visited by friends and relatives. 29 October: The patient himself suspected smallpox, but through fear of being sent to an isolation camp, did not inform the authorities. 30 October: A male nurse from the hospital reported the case to the Regional Health Superintendent. 31 October: The smallpox eradication programme epidemiologist was informed, investigated the case and diagnosed his illness as smallpox. On 31 October, when first examined, the lesions were pustular and discrete, with many more lesions on the extremities, including the palms and soles, than on the trunk. The patient subsequently recovered and was discharged from the isolation centre at the end of November. Specimens for laboratory diagnosis were collected on 31 October and the diagnosis confirmed by iso- lation of variola virus at the WHO Collaborating Centre at the Center for Disease Control, Atlanta, USA. The source of infection was quickly identified. On the evening of 12 October, two smallpox cases, de- tected about 17 km north of Kurtunwarey settlement (Fig. 2), had been sent in a vehicle to an isolation camp near Merca. The vehicle had stopped at Merca Hospi- tal to seek directions. Ali Maalin had travelled in the vehicle to direct it to the home of the local smallpox surveillance team leader. His contact with the patients, a 6-year-old girl, Habiba Nur Ali who had severe smallpox, and her l-year-old brother then in the papular stage of the rash, lasted for not more than 15 minutes. The patients from Kurtunwarey were isolated but follow-up investigation at that time failed to identify Ali Maalin as a contact. The chain of transmission, resulting in this last smallpox outbreak was traced back to mid-August, when the first smallpox case had occurred among a nomadic community of 20 families with a total of 109 persons, staying in Xaargarsal area in Koryole District. In all, eight smallpox cases, including the two mentioned above, had occurred among these nomads during their two months' movement through Koryole, Brava, and Kurtunwarey districts (Fig. 2). The last case occurred on 18 October at Edi Shabelli. Containment measures Additional national and WHO epidemiologists were immediately transferred to Merca from other posts and a detailed plan of action was formulated. Isolation of the patient. Initially, the patient was isolated at his home, a room that he rented approxi- mately 200 m from Merca Hospital, and day and night guards were posted. However, since his home was located in a densely populated urban area, it was decided to transfer the patient to an isolation camp at El Warego about 10 km from Merca on 2 November. One police guard and one militia guard lived perma- nently at the isolation centre until the patient was dis- charged four weeks later. Contact tracing. Possible contacts included all hospital staff, medical and surgical ward patients from 21-27 October, visitors to the medical ward on the days of the patient's hospitalization, and his family, neighbours, and friends who had visited him in the hospital or at home. Also to be considered were others in the town who might have been exposed during the prodromal period. A total of 161 possible contacts were identified, located, and interviewed. Some were from localities more than 120 km away. Contacts were classified according to the intensity of their exposure and the presence or absence of vacci- nation scar resulting from vaccination within the previous three years (Table 1). Possible contacts without evidence of successful vaccination within the preceding three years were considered "unprotected". Individuals who had been in the same place with the patient at some time since the day before the onset of fever, but who had not had close exposure, were considered as "incidental contacts". Of 33 face-to- face contacts who had no evidence of successful vacci- nation within the previous three years, 12 had no vaccination scar from earlier vaccination either and were considered to be at maximum risk. All known and possible contacts and members of their families were vaccinated. Incidental contacts were visited at least twice, "protected" face-to-face contacts were visited an average of four times each, 281 A. DERIA ET AL. and those classified as unprotected, six times each during the 18 days following contact. During the sur- veillance period, two hospital employees and three neighbourhood contacts developed fever and were placed in isolation in their homes; none developed a rash Nn sPcnndarv caspz nrcurrpdimnno the IAI __ contacts. Table 1. Classification of pos exposure and vaccination stati Vaccination status prior to exposure vaccinated within past 3 years vaccinated more than 3 years previously unvaccinated /without vaccination scar total Face Measures at Merca I numerous contacts with the tal, the following measures (a) all patients were va, and admissions were restric (b) all outpatients were facilities; (c) all health staff in the household members, were (d) all hospital staff ar daily for fever; (e) warning signs were p guard was posted at the ho Patients were permitted to leave the surgical ward on 13 November and the medical ward on 17 November. Vaccination and search forfurther cases -t ' '' Of greatest concern was Horseed Ward, where the patient's house and Merca Hospital were located. Immediately, the patient's house and the 50 closest neighbouring houses were visited by a two-man team of local residents who listed and vaccinated all inhabi- sible contacts by degree of tants and visitors. Teams, each comprising two small- us pox programme staff, one local party leader, and one policeman, visited the remaining houses of Horseed )egree of exposure Ward. The teams worked at night to achieve the maxi- e-to-face Incidental Total mum possible vaccination coverage of the population. A first round of vaccination was completed by 2 November. 58 62 120 Thereafter, a team of ten persons was assigned to revisit all households in Horseed Ward searching for 21 8 29 smallpox cases, vaccinating newly-returned residents or visitors and revaccinating those whose first vacci- nation was unsuccessful. In the remaining two wards, 12 0 12 Wadajir and Hawl Wadag, the team visited all houses, listing and vaccinating all residents during the follow- 91 70 161 ing seven days. By 10 November, the entire town of Merca had been covered by one round of search and vaccination. This intense activity was followed by repeated three-day searches of the entire town during each of the six weeks of the observation period lospital. Owing to the (Table 2). pihpi- With police assistance, a checkpost was establishedpatient while at the hos on the road into Merca to stop all traffic entering or were taken: leaving and to vaccinate all passengers. Three ad- ccinated and quarantined ditional checkposts covered the three footpaths into cted to emergencies only; Merca. These fixed vaccination/surveillance posts referred to other health were maintained for six weeks. Public meetings were held in the orientation centres of all wards to inform town of Merca, as well as the public about the smallpox emergency, the actions vaccinated; being taken, and the need to report illnesses with rash id patients were checked to health authorities. A reward of 200 shillings (approx. US$ 30) for reporting a smallpox case was osted and a 24-hour police widely publicized as was the location of vaccination spital entrance. centres. Table 2. Results of containment, vaccination, and search operations in Merca, November 1977 No. of No. of rash cases detected No. of persons Area Period houses Population vaccinated Smallpox Chickenpox Others Horseed 31.10 - 2.11 792 5 000 3 558 0 1 4 Wadajir 3.11 - 6.11 738 4 300 2 873 0 1 1 Hawl Wadag 7.11 - 13.11 1 007 10 500 8 092 0 1 6 checkposts 31.10 -14.11 - - 40 254 0 0 0 282 WORLD'S LAST ENDEMIC CASE OF SMALLPOX Follow-up surveillance No further smallpox cases were found in the town of Merca or in Somalia during the six weeks following the last case. During the four subsequent months (November 1977-March 1978), five house-to-house searches were conducted in the affected district and throughout Lower Shabelli Region (Table 3). Again no cases were discovered. Continuing searches throughout 1978 and 1979 detected no evidence of smallpox. The case described remains the world's last known occurrence of endemic smallpox. In retro- spect, it can be seen to have occurred as the result of a combination of errors and omissions. However, prompt and comprehensive containment and an element of good fortune confined the outbreak to a single case. Ali Maow Maalin was thus the world's last case of endemic smallpox. Table 3. Summary of search activities in Lower Shabelli Region, November 1977 - March 1978 No. visited No. of rash cases and searched detected Month Nomad Small- Chicken- Villages camps Houses Schools pox pox Others November 786 239 62 676 598 0 9 362 D1c977be 1 328 341 102898 900 0 16 454 January 1576 550 104 818 1000 0 11 2041978 February 1 064 240 79843 1 053 0 11 70 1978 March 1978 1 230 586 77 287 948 0 13 27 ACKNOWLEDGEMENTS We gratefully acknowledge the vital role played by the Lower Shabelli smallpox and health staff, headed by Dr Abdi Abdullahi and Mr Bashir Ali Roble, in both containment and surveillance. Furthermore, we should like to acknowledge the contribution of Dr Al Aghbari, Dr Hardjotanojo, and Mr Hatfield who assisted in investigations and supervision of containment acitivities, especially during the first days of the outbreak. Our gratitude is expressed to the Lower Shabelli administrative and political officials who quickly and effectively organized general public support, understanding, and cooperation. Finally, a special acknowledgement to Dr D. A. Henderson and Dr I. Arita, who in spite of intensely busy professional lives were able to find time to edit this article. RESUME LE DERNIER CAS DE VARIOLE ENDEMIQUE QUE LE MONDE AIT CONNU: MESURES DE SURVEILLANCE ET D'ENDIGUEMENT Le 31 octobre 1977, le dernier cas de variole endemique que le monde ait connu a ete decouvert A Merca, en Somalie. L'origine de l'infection fut tres vite identifiee; 19 jours auparavant, le patient avait e en contact avec deux vario- leux pendant une quinzaine de minutes tout au plus, et le dis- positif de surveillance mis en place n'avait pas permis de reperer ce contact. Le patient fut isole, tandis que des mesures d'endiguement et de surveillance ainsi qu'une cam- pagne de vaccination etaient rapidement instituees; on identifia 161 contacts, dont 41 n'avaient pas et vaccines depuis trois ans. Le patient se retablit et on n'eut heureuse- ment A enregistrer aucun autre cas. 283