Revisiting 1957-1958 influenza pandemic may provide clues to combating H1N1

Similarities between Asian influenza (H2N2) and H1N1 pandemics may exist.

Issue: September 2009

A review of the H2N2 Asian influenza outbreak of 1957-58 may be useful in planning strategies to combat the current H1N1 pandemic, according to researchers from the Center for Biosecurity at the University of Pittsburgh Medical Center.

Both pandemics were marked by widespread outbreaks in the spring after developing at the beginning of the year. The clinical presentation of cases and transmission patterns of the current pandemic are similar to that of 1957, according to the researchers. In both cases, the disease was not particularly severe and preliminary data indicate that the case-fatality ratios of the two pandemics may be comparable.

Donald A. Henderson, MD, MPH, is a Distinguished Scholar at the University of Pittsburgh Medical Center and Center for Biosecurity. He was working at the CDC in 1957 and was involved in the publication of the current article.

“I would hesitate to say that this provides an absolute blueprint of what will happen in 2009,” Henderson said in an interview with Infectious Diseases in Children. “However, from what we have observed thus far, the pattern of occurrence of cases, in terms of severity and contagiousness, really do not look very different from what we had then. What we had then was a virus that had shifted its antigenic character leaving a population with no previous experience in dealing with a virus of this type. Thus, it was an influenza strain entering a population that had no immunity to it. It was similar to the pandemic we are experiencing this year.”

Henderson said that in the summer of 1957, CDC decided to create an Influenza Surveillance Unit to monitor the behavior of the virus. Strategies implemented by this unit included county-level reports, a national health survey and observation of absenteeism in schools, various industries and hospitals.

Though the outbreak appeared to decrease toward the end of the summer, the beginning of the school year in late August brought a new wave of infections.

“What we went through in the summer of 1957 was very similar to what has been happening in 2009,” Henderson said. “There were a number of outbreaks in camps and conference centers, sometimes with attack rates as high as 40% but with little spread throughout communities. This makes us wonder if the similarities will continue and that we will experience widespread outbreaks coincident with schools opening in the fall.”

Vaccine

There was some debate at the beginning of the 1957 outbreak as to whether dramatic measures such as school closings should take place, but those efforts were abandoned. Thus, the cornerstone of the disease containment effort focused on production and implementation of a vaccine and preparations for care of patients.

“The early stages of the 1957 outbreak were not marked by a dramatic series of events,” Henderson said. “So there was a sort of ‘British resolve approach’ to dealing with it. Maintaining the continuity and integrity of community activities was deemed most important, so there were no recommendations to close schools or postpone major meetings.”

Henderson said that because of this, an effective vaccine program became the de facto key to combating the pandemic. Vaccine production was accelerated but only limited amounts were available in time. By November, epidemic cases were declining rapidly but vaccine enough for only 17% of the population had been received. It was too little and too late to thwart the epidemic. It was estimated that, overall, 25% of the population had experienced illness.

As the epidemic waned, interest in vaccination declined sharply but, in the new year, there was an unexpected recurrence of the disease with an increase in deaths due to pneumonia and influenza from January through March.

Henderson said this is important to keep in mind as public health officials continue to make plans to battle the current epidemic. “It is worth pressing on with vaccination, even if the infection rate drops off in the late fall,” Henderson said.

Though there are lessons to be learned regarding vaccine production from the 1957-1958 pandemic, Henderson said that concerns about avian influenza in 2004 had already begun to drive the need home. “We saw the need to have multiple manufacturers producing the vaccine,” he said. “There was need to streamline the process of production and learn how to grow the virus in great quantities at a rapid pace. Ideally, we need to have a vaccine that provides a more broad-based immunity that is good for several years.”

Beyond vaccine production, Henderson said that hospitals and clinics need to be prepared for a potential influx of H1N1 cases. “I do not believe that we are going to see more than 25% of the population getting sick, and I do not believe that an outbreak will last very long,” he said. “But I think level-headed communication from the CDC through to the clinic and ICU could go a long way in keeping this infection at a manageable level.” – by Rob Volansky

Henderson DA et al. Biosecurity and Bioterrorism: Biodefense Strategy, Practice and Science. 2009;7:1-9.