House on Fire (13 page)

Attitudes were changing by 1968, but the herd immunity strategy still drove WHO's thinking.

The twenty-country program yielded several new insights into the epidemiology of smallpox, each of which helped to refine the eradication strategy. Both folklore and textbooks described smallpox as a disease of rapid transmission. In fact, the CDC workers discovered that the virus spread with more difficulty than expected, often requiring multiple incubation periods even within one household or compound. The virus's tenacity in continuing to infect new generations within a household was confused with high transmissibility, which explains its false reputation as a highly contagious disease. This understanding of the epidemiology meant that the natural progression of an outbreak could indeed be interrupted.
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We also observed the accumulated wisdom of countless generations who had faced the disease. During an outbreak temporary structures were constructed outside a village to house patients. Persons who had recovered from smallpox were in charge of bringing food to the patients and caring for them. It was common knowledge that having had the disease
itself provided solid immunity. Experience also showed that few people who had a visible smallpox vaccination scar got smallpox, and that cases were extremely rare in persons with a history of a second vaccination.

Gradually, we also discovered that the incubation period for vaccinia virus, the virus used in vaccine, was slightly shorter than the incubation period for the smallpox virus itself. Therefore, vaccinating a person on the day of exposure to smallpox could prevent the disease. Indeed, we eventually learned that vaccination even several days after exposure could prevent or at least reduce the severity of the disease. In the race between the two viruses, the vaccine virus could win.

Was the surveillance/containment strategy that was proving so effective with smallpox new or not new? The two basic parts of the strategy were not new. Surveillance is the basis for all disease control programs at CDC and elsewhere in the world. One could not work at CDC without deeply internalizing the idea that disease control requires accurate knowledge about the disease and its environment and that this knowledge is obtained through surveillance systems. Response, or control, was based on surveillance findings.

The global smallpox program was designed to reduce smallpox virus transmission by means of mass vaccination to a point where attention could be placed on individual outbreaks and chains of transmission. The WHO program, from the beginning, envisioned surveillance and containment as the follow-on strategy after mass vaccination. Henry Gelfand and D. A. Henderson describe the original strategy for the West Africa program in a 1966 article in the
Journal of International Health.
They state that the goal of the program “being eradication, an attempt will be made to vaccinate the entire population, regardless of age or previous vaccination status, in as short a time as possible”—in other words, to do mass vaccination. They go on to say that this will probably take two or three years. Because 100 percent coverage is unrealistic, “a second
mass cycle of vaccination will probably be carried out within the 5-year lifetime of the program.” In addition, they say that because disease surveillance is “grossly incomplete,” the “epidemiologists will be intimately concerned with the mobilization of every available reporting source . . . so that no case of smallpox will go unreported and uninvestigated.” The idea was to pinpoint areas of transmission not eliminated by mass vaccination. Finally, they list what they regard as the more important new elements of the program. These included a regional approach, the use of lyophilized vaccine and jet injectors, a systematic assessment and surveillance program, and adequate resources.
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The handbook for all CDC workers in the program, titled
West and Central African Smallpox Eradication/Measles Control Program: Manual of Operations,
clearly sets out the program's expectations: to develop a mass vaccination program and to complete the program within three years, before immunity could wane:

Since the target with respect to smallpox is eradication, a finite goal, and since this involves a careful systematic vaccination of all ages and segments of the population, operational procedures and techniques focus principally on smallpox vaccination . . . smallpox eradication will be realized by successfully reducing, through vaccination, the number of susceptibles in the West African population to the point where it is impossible for the disease to sustain itself in a continuous chain of transmission.

Since the objective of the vaccination campaign is to induce a high level of immunity in the population . . . [and since] after three years, the proportion of persons with full immunity falls gradually and “breakthroughs” become more frequent . . . obtaining total coverage in three years requires realistic planning.
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In fact, the manual included a warning to not let outbreak containment divert efforts from the mass campaign during the three years. “The need may occasionally arise for a rapid vaccination effort in an area to control an outbreak. In pre-planning, provision should be made for handling these situations. For completion of the attack phase on schedule, the time table drawn up for area coverage should be reasonably strictly followed. If vaccination teams are frequently forced to disrupt
their activities to perform mopping up or ‘fire fighting' operations, great damage will be done to the orderly progress of the campaign.”
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Surveillance/containment approaches were not new to the CDC team. Vaccinating those at highest risk of exposure makes logical sense and had been used frequently. Indeed, it was endorsed by a royal commission in England as early as the 1890s. Surveillance/containment was also written into plans for the containment of a possible smallpox importation in various cities (such as New York) and had been used for outbreak control in many countries, especially importations of smallpox into Europe in the twentieth century. As already mentioned, it was also the follow-on plan in the WHO program after mass vaccination had reduced the intensity of transmission. This was the reason for developing the surveillance system for identifying all cases of smallpox. While surveillance/containment was the logical follow-on to mass vaccination, it was always seen in a secondary role, never as the primary strategy and certainly not as a substitute for mass vaccination.

After the positive results in Ogoja province (and later in the entire Eastern Region of Nigeria), however, surveillance and containment began to be seen as the
primary
strategy for smallpox eradication. This had not been presented as an option in our training before we left for Africa. The lessons learned in the outbreak in Ogoja province led eventually to the abandonment of mass vaccination as the primary strategy in other countries and finally in all countries as eradication activities rapidly accelerated. When surveillance and containment are made the primary strategy, mass vaccination can be dropped totally. In fact, it becomes a wasted effort.

In retrospect, it is easy to see why surveillance and containment worked so well for this particular disease. The presence of the virus was easy to detect, since almost everyone infected developed lesions, mostly on the face and extremities, where they were easily seen. Moreover, most people who acquired the virus became so severely ill that it stopped their movement. Family, friends, and community members were likely to be aware of cases. Even if a patient remained undetected from the first day of the rash, the chain of transmission didn't remain hidden for long. Even if only a single person was infected during each incubation period,
which is two or three weeks, only twenty persons were needed to keep a single chain of transmission intact for a year. If any one of those twenty people failed to pass the virus on, the chain was broken. In fact, in most cases, an annual chain involved hundreds of people, making the virus easy to find.

Not only did the virus have difficulty remaining incognito during the illness, it also left a trail after the fact. Pockmarks, especially on the face, told the story of the virus's visit. Surveys of a village quickly revealed the last time the virus was active in the community, based on the age of the youngest people showing scars. The bottom line is that unlike many other viruses, smallpox virus simply could not hide. It left too many clues.

The ease of identifying the smallpox virus is highlighted by an incident in November 1971. Smallpox workers at the CDC in Atlanta watching the nightly news happened to see a report about refugees leaving Bangladesh, bound for India. One of the refugees in the film clip appeared to have smallpox. The Atlanta observers called the report in to WHO in Geneva. The WHO alerted officials in India, who alerted local workers, and the following day the outbreak was found and contained.

Surveillance and containment also works particularly well for smallpox because the virus is so specialized. It can only commandeer human cells. Over the centuries it must have tried repeatedly to adapt to other species, but without success. The smallpox virus must find a new, susceptible host within weeks of initiating disease in a person or it will die. The virus also dies quickly outside the human body unless it is kept in freezing conditions. It turned out that a perimeter containing no susceptible people needed to extend for only a half-dozen feet from the person with smallpox to be effective. Therefore, once the virus was located, vaccinators could concentrate their efforts on vaccinating anyone who might have come within that perimeter. It was necessary, of course, to prevent the virus from traveling out of that protective bubble on contaminated clothes—just as firefighters must prevent a fire from crossing a fire line.

Although the surveillance/containment method worked exceedingly well for smallpox, this does not mean it would work as effectively for other diseases. The smallpox eradication story contains many lessons,
but giving up mass vaccination as a methodology for other diseases is not one of them. Rather, the lesson is that every problem has to be considered individually.

Our experience in Eastern Nigeria and then in West and Central Africa was compelling. Surveillance/containment was eventually used as the primary strategy in all areas of the world in the smallpox eradication effort. It would be refined and tested to the utmost and would provide its most dramatic results seven years in the future, in the state of Bihar, India. But it started that night in Ogoja province during a problemsolving discussion about inadequate supplies.

 

 

 

 

As the new decade began, the win column in the global effort to eradicate smallpox started to lengthen. In January 1971, nine months after the last smallpox case in West and Central Africa, Brazil reported its final case. Three months later, Indonesia became free of smallpox. By the end of the year, only nine countries still had continuous smallpox transmission. In July 1972, Afghanistan became smallpox free.

Yet even as the number of countries with smallpox was declining, progress was disappointing in the four smallpox-endemic countries of South Asia: Bangladesh, India, Nepal, and Pakistan. In India, a new mass vaccination campaign, the fourth within ten years, was having little impact. There was strong feeling both inside and outside the country that smallpox in India was different, that success in other places simply underscored the problem. Even experienced public health workers, including some with extensive experience in the Africa smallpox program, came away frustrated, concluding that the problems of smallpox
in India could not be approached in the same way as elsewhere. In India, it seemed, smallpox was inevitable.

By this time I was back in Atlanta, working at the CDC as director of the smallpox program. Dr. David J. Sencer, then director of CDC, had a passion for getting smallpox eradicated. He was a bright, dedicated physician who took delight in solving problems.

The CDC had remained involved in the WHO global program even after eradication was accomplished in West and Central Africa. At the beginning of the program, Leo Morris was assigned to work in Brazil, and then a flood of CDC people were assigned around the world. Most were assigned through WHO, but a few were assigned directly on a bilateral basis. CDC staff traveled frequently in response to WHO requests, evaluating programs and attending WHO-sponsored meetings. The working relationship between CDC and WHO was so close that any jurisdictional issues or turf problems could be negotiated. The combined heft of the two agencies was often important, since public health officials looked to the CDC on questions of science but expected consultants to come with a WHO stamp of approval.

I found that the ideal position was to be seconded, that is, loaned, by CDC to WHO for work in the field. I used my WHO position when working with administrative or political staff and my CDC position when working with scientific staff. Most work straddled both areas. Because of my experience with the surveillance/containment methodology, I was often asked to present at WHO meetings in various parts of the world.

The surveillance and containment method had been promoted at every global smallpox meeting since the regional meeting in Accra in July 1967. The idea was strongly pushed in letters from WHO/Geneva to the WHO regional office in New Delhi. However, surveillance and containment as the primary strategy was simply not imagined in India. Many seriously doubted that smallpox transmission could be interrupted in high population density areas where smallpox was endemic. Henry Gelfand, for instance, a longtime CDC public health worker, had been part of an evaluation of smallpox in India that recommended virtually 100 percent vaccination coverage as the only way to interrupt smallpox transmission in that country.