House on Fire (10 page)

As the CDC smallpox eradication teams established programs in West and Central Africa in late 1966 and into 1967, they followed the same plan that vaccinators had followed for seventeen decades: to vaccinate as many people as possible. This method provided direct protection for the person vaccinated and aimed to accomplish “herd immunity”—indirect protection for unvaccinated persons who would have acquired smallpox if the vaccinated person had become sick. There is no question that mass vaccination could work, as was demonstrated early on in Ceylon (now Sri Lanka)
and later in Bolivia, China, and in many countries of the industrialized world.

The problem with mass vaccination is that an exceedingly obsessive program is required to make inroads into the last 20 percent of any population. The segments of the population most difficult to reach with vaccine—the drifters, the marginalized populations, beggars, itinerant workers—are often the ones most at risk of both getting and spreading the disease. Therefore, surveillance and containment of outbreaks was seen as the next step after mass vaccination. Add to this the high population densities in urban areas and it becomes clear that herd immunity is easy in theory but not fully effective in practice. Even with a good program, a critical mass of unprotected persons can accumulate, and the vulnerability of such unvaccinated pockets often leads to an explosive outbreak when the smallpox virus is reintroduced. This problem is well recognized in public health. Yet at the time it was the best plan anyone had. My CDC colleagues and I working in Eastern Nigeria embraced this strategy, and during the final months of 1966 began making plans to pursue it with determination.

Serendipity provided a chance for us to rethink the eradication strategy before the year ended. On December 4, 1966, Hector Ottemüller, a longtime missionary in the Ogoja area, contacted me by radio. There was an outbreak of smallpox in the village of Ovirpua, in the Alifokpa area of Ogoja province, some ninety miles northeast of Enugu, and Hector was asking if the smallpox unit could help. Ottemüller was a minister by training, with a patriarchal bearing enhanced by striking white hair and a white beard. His consuming interest lay in improving the lives of the people in his rural area. He was involved in agriculture and water supply schemes, although the people also called upon him for health advice. Thus it was not surprising that he was the first to receive the report of a rash disease feared by all in his area.

The village of Ovirpua was some miles from a road, but Dave Thompson and I managed to get hold of two Solex motorbikes, which were ideal for this work. Made in France, they are essentially sturdy bicycles with a small motor that engages directly on the rubber of the front tire, and they are lightweight enough to be carried under one arm across logs spanning creeks. We arrived at Ovirpua in mid-afternoon. The first person I examined was a young man in his twenties, and there was no question about the diagnosis. We examined and questioned four other people who had the disease. We vaccinated the patients' family members and other villagers in immediate contact with them.

Figure 5.
First smallpox patient seen in Ogoja, Nigeria, outbreak, December 4, 1966

That night, Thompson and I and several missionaries assembled around kerosene lamps in the house of a missionary who lived in the area. We talked through the problem while educating the missionaries about the sobering situation we were facing. We knew this was smallpox but we did not know its extent. How many villages were involved? How many people were sick and how many were in the incubation period? Had it just been introduced to the area, or had it been smoldering for some time?

The standard response was to vaccinate everyone within a certain radius while attempting to determine the extent of the outbreak. However, we did not have enough vaccine to do this. The program was so
new that supplies had not yet arrived in quantity, and there was no likelihood of quickly receiving more. How could we most efficiently use the limited amount of vaccine we had on hand?

It was tempting to consider diluting the vaccine so we could vaccinate more people. However, history showed that this was a risk that should not be taken. In 1962, Dr. Robert Hingson, founder of the Brother's Brother Foundation, committed to vaccinate Liberia's population of about 1.3 million people against smallpox. A massive campaign was undertaken, but the program organizers found that they had underestimated their vaccine needs, so they diluted the vaccine fifteen-fold. A subsequent assessment by WHO indicated that only 60 to 70 percent of the population had successful primary vaccinations, and 325 cases of smallpox were reported in Liberia the same year, after the campaign ended.
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Some people who had been vaccinated subsequently got smallpox, probably because of the vaccine dilution. If we now did the same thing, we could be leaving unprotected an unknown number of people who were directly in the viral path.

Forced to look for another solution, we raised the question: if we were smallpox viruses bent on immortality, what would we do to extend our family tree? The answer of course was to find the nearest susceptible person in which to continue reproduction. Our task, then, was not to vaccinate everyone within a certain range but rather to identify and protect the nearest susceptible people before the virus could reach them.

What we knew about the virus's behavior also figured into our strategy. The smallpox virus poses little risk to people other than its host during the incubation period. It is only when the characteristic sores form on the skin and mucous membranes that the virus can escape the host and seek new victims. Spread is also easiest during the early days of rash, when the number of virus particles on the body's surfaces is large and people may not yet recognize the disease. The potential for spread decreases as people become wary, and as the host's immune mechanisms respond and the number of viruses on the patient's exterior declines. Spread is most likely within the first week of clinical symptoms and is probably rare after three weeks.

We discussed the risks of spread. The highest spread potential was
obviously in the home, but early in the illness the patients might also have been in contact with visiting relatives or might have attended one of the region's markets. We could use the missionaries' knowledge of market patterns and family patterns to make predictions about high-risk areas for spread, but first we needed to know where the virus was at that moment.

Acquiring this type of intelligence would be difficult even in a country like the United States. It seemed absolutely impossible in rural Africa. However, the missionary community's own support system offered an answer. There were no telephones, so every night at 7
P.M.
, the missionaries turned on their shortwave radios and checked in to make sure that no one was in need of assistance.

We weren't that hopeful, but it was worth a try. That night we got on the radio with missionaries up to some thirty or more miles distant, explained the situation, and, with maps in front of us, divided up the area. We asked each missionary to send runners to every village in his assigned area to ask if anyone had seen cases of smallpox.

The following night Thompson and the local missionaries and I again got on the radio, and to our joy and amazement were given the precise information we needed. Only four villages had smallpox cases at that moment. The rest were free of the disease.

Our plan was straightforward. First, we vaccinated the currently infected villages, where some people were probably already infected even if they had not yet developed symptoms. For those recently exposed, vaccination would greatly reduce the disease's impact, if not prevent it. Those exposed even two weeks earlier would still get smallpox, but they would be surrounded by vaccinated people, making further transmission of the virus very difficult. If we were fortunate, it might even stop transmission totally.

Second, based on the missionaries' knowledge of where the patients and their families usually traveled, we made some informed guesses regarding other places where the virus was most likely incubating. We identified three, all within a fifteen-mile radius, and decided to use the remaining vaccine there. We could not know as we vaccinated these three additional areas that smallpox was already incubating in two of them. By the time clinical cases were detected in these two places, the remaining population was already protected—and smallpox was stopped in its tracks. The outcome was the complete cessation of this outbreak.

Figure 6.
Patient outside the infectious disease hut near Abakaliki, Nigeria, 1967

“Life accumulates” was a favorite saying of Jim Laney, former president of Emory University. In many ways the strategy that stopped the virus was a logical extension of the firefighting principle I was taught back in the summers of 1956 and 1957. By removing the fuel one step ahead of the virus, we had built a fire line around it.

Dave Thompson, Paul Lichfield, and I had no way of knowing that this new approach was going to work as well as it did, so during the subsequent weeks as the scenario in Ogoja province unfolded, we acquired more vaccine and, with the help of the missionaries, expanded vaccination
coverage in the area. However, once the transmission ceased, we realized that these additional vaccinations, while building herd immunity against a future outbreak, did nothing to stop the current outbreak. If smallpox never returned to this area (and it never did), then every additional vaccination was essentially wasted effort—a theft of time and vaccine. Even on this small scale, we were seeing the inefficiency of mass vaccination.

Despite this success, we did not immediately abandon the mass vaccination approach. Indeed, we went ahead and implemented it because that is what we had been sent to do. After Christmas, we began training teams of health workers from the Eastern Nigeria Ministry of Health. We used stopwatches to see how fast they could set up an immunization site, drive in stakes, attach ropes for crowd control, clean the jet injectors, set up one injector for smallpox vaccine and another for measles vaccine, and when all was in order, give the first immunization. The teams became proficient and even competitive in demonstrating their skills.

Once the teams were trained, we ran a vaccination pilot project in Abakaliki, a city located east of Enugu. The project was nearly perfection in execution, community involvement was high, and our evaluations showed that we had vaccinated over 94 percent of the population, an incredible coverage rate at any time but especially impressive as a first effort.

We had barely finished congratulating ourselves when a smallpox outbreak was reported in Abakaliki. We were sure there must be some mistake, but investigation confirmed that it was definitely smallpox. We figured that the outbreak was in a small geographic pocket of people that had somehow been missed. But as the number of cases mounted, we were surprised to find them distributed throughout the city. All of the infected people turned out to be members of a religious group, the Faith Tabernacle Church, that had refused vaccinations based on religious convictions. They comprised a missed pocket but not a geographic pocket.

This experience altered our thinking. Clearly, mass vaccination could protect the vast majority of a population without guaranteeing that smallpox transmission would cease. This reinforced the lesson of the Ogoja outbreak—that there might be a better way.

 

 

 

 

In the first weeks of 1967, Dave Thompson, Paul Lichfield, and I made a choice we could not have predicted. As we designed the eradication project for Nigeria's Eastern Region, we also researched smallpox reports from past years. We recorded the previous outbreaks by date and place on maps of the region, and as we did, a macro pattern appeared. At the beginning of most high-transmission seasons, smallpox outbreaks were generally more prevalent in the northern part of Eastern Nigeria, suggesting that they migrated in from the Northern Region and gradually moved southward. We wondered initially if we could impede the progression, and thus stop smallpox, by building a fire line of mass vaccinations across the northern part of the region. The results in Abakaliki, however, were compelling and gave us pause, especially as they followed so soon after the dramatic results in Ogoja. We decided that the surveillance/containment approach ought to be tested in a larger area.