Coronavirus: How social distancing led to 50% decrease in death rates during the Spanish Flu
Places that were once teeming with daily life have become ghost-towns due to massive restrictions, including social distancing and lockdowns. But can social distancing check the spread of COVID-19? Data from the 1918 pandemic flu, also referred to as the Spanish flu pandemic, suggests that strict social distancing and other measures slowed the disease spread and decreased death rates by up to 50% in cities that used them.
Recently, a series of public health measures have been taken to reduce the spread of the disease in the US and across the globe. These “social distancing” measures vary across states and cities but are generally wide-ranging. They include complete lockdowns, canceling sports, music, cultural, political events, and the closing of gyms, schools, and colleges. It also includes recommendations to work from home, to avoid discretionary travel, to avoid eating or drinking in bars, restaurants and food courts, and avoid social gatherings in groups of more than 10 people. US President Donald Trump recently extended social distancing guidelines to April 30.
This situation is not unprecedented, although the 100-year-old precedent is mostly forgotten, say experts. According to a review paper, during the 1918 influenza pandemic caused by the H1N1 virus, the US adopted similar measures known as non-pharmaceutical (public health) interventions. The analysis shows that in some cities — San Francisco, St Louis, Milwaukee and Kansas City — where the measures were implemented early, transmission rates went down by up to 30-50%. The findings have been published in the Journal of the American Society of Cytopathology. The H1NI virus spread worldwide during 1918-19 and the pandemic is estimated to have infected a fifth to a third of the world population and during which 50 million people died globally, including an estimated 675,000 Americans,
“I believe that they should be kept in the US until at least mid-to-end May, but that is just a guess, and I am generally an optimist. In 1918, cities that have discontinued the "social distancing" measures had a second and sometimes even a third wave of cases,” the review paper’s corresponding author, Dr Stefan E Pambuccian, Department of Pathology and Laboratory Medicine, Loyola University Chicago Stritch School of Medicine, Loyola University Medical Center, told MEA WorldWide (MEAWW).
“Obviously the situation was much different, there was a war going on, with patriotic rallies through the streets of major cities, and then peace (armistice) celebrations, and then finished, with greater than 1 million US soldiers returning from Europe. Also, the infectivity rate (R0), and even case fatality rate of the 1918 H1N1 influenza was much higher than that of the current COVID-19 (SARS-CoV-2) pandemic,” he told MEAWW.
The number of reported cases in the COVID-19 pandemic has crossed one million globally, and over 53,000 have died, according to the John Hopkins tracker. In the US, more than 245,000 cases have been reported and over 5,900 have died.
Tale of two cities
In a 2007 study, researchers analyzed data on the timing of 19 classes of non-pharmaceutical measures (NPIs) in 17 US cities during the 1918 pandemic. They found that cities in which multiple interventions were implemented at an early phase of the epidemic had peak death rates 50% lower than those that did not and had less-steep epidemic curves.
To further illustrate this point, the authors of the 2007 study compared the impact of the difference in response times between US two cities: Philadelphia and St Louis.
The first cases of disease among civilians in Philadelphia were reported on September 17, 1918, but authorities downplayed their significance. Social distancing interventions were not implemented until October 3, when disease spread had already begun to overwhelm local medical and public health resources. In contrast, the first cases of the disease in St Louis were reported on October 5, and authorities moved rapidly to introduce a broad series of measures designed to promote social distancing, implementing these on October 7.
“The difference in response times between the two cities (14 days, when measured from the first reported cases) represents approximately three to five doubling times for an influenza epidemic. The costs of this delay appear to have been significant. The costs of this delay appear to have been significant,” says the study that was published in PNAS.
It explains, “Philadelphia ultimately experienced a peak weekly excess pneumonia and influenza (P&I) death rate of 257/100,000 and a cumulative excess P&I death rate (CEPID) during the period September 8–December 28, 1918 (the study period) of 719/100,000. St Louis, on the other hand, experienced a peak P&I death rate, while NPIs were in place, of 31/100,000 and had a CEPID during the study period of 347/100,000.”
The findings suggest that such interventions may be capable of significantly reducing the rate of disease transmission so long as they remain in effect, say experts.
However, the NPIs used in 1918 did not last indefinitely; rather, most cities appear to have relaxed them within two to eight weeks, whereas opportunities for reintroduction and transmission of the pandemic virus extended for many months. They say in the absence of an effective vaccine, cities that use NPIs to mitigate the impact of a pandemic remain vulnerable. In practice, and until emergency vaccine production capacity increases, this means that in the event of a severe pandemic, cities will likely need to maintain NPIs for longer than the two to eight weeks that was the norm in 1918.
“Early implementation of certain interventions, including the closure of schools, churches and theaters, was associated with lower peak death rates, but no single intervention showed an association with improved aggregate outcomes for the 1918 phase of the pandemic. These findings support the hypothesis that rapid implementation of multiple NPIs can significantly reduce influenza transmission, but that viral spread will be renewed upon relaxation of such measures,” says the study.
A recent study also said a single period of social distancing will not be sufficient to prevent critical care capacities from being overwhelmed by the COVID-19 pandemic. The reason: Once such restrictions are lifted, the virus would, in all probability, come roaring back. Accordingly, says the research team, on its own, social distancing may need to be maintained intermittently into 2022 to avoid overwhelming critical care capacity. Another report by the from Imperial College London, UK, also says the effectiveness of any one intervention in isolation is likely to be limited, requiring multiple interventions to be combined to have a substantial impact on transmision.
Current review
The review study also emphasizes that the duration that these “social distancing” measures were kept in place correlated with a reduced death burden. The team says though currently there is no known effective therapy or vaccine prevention for COVID-19, and the world is a quite different place than it was 100 years ago, the efficacy of the measures instituted during the 1918 pandemic gives hope that the current measures will also limit the impact of the COVID-19 pandemic.
The social distancing measures currently in place for COVID-19 pandemic are meant mostly as a mitigation strategy, to limit transmission. It is also aimed at preventing the fast spread of the virus and “level the infection curve” to prevent overwhelming the healthcare system.
“With flattening the curve, we also widen it, the flatter, the wider. So, instead of having a peak that would have overwhelmed us -- resulted in an unacceptably high number of fatalities and disrupted the health care sector, but would have subsided in two-three weeks (until all susceptible individuals would have gotten infected, and either recovered or died) -- with social distancing measures, we are looking at maybe less than 50% of cases and fatalities that would have occurred without them, but spread over a much longer time, I would guess two-three months,” Dr Pambuccian told MEAWW.
He added, “It may be economically impossible to continue these measures as long as they would be needed from an epidemiology point of view, because, apart from a serious disruption of the entire economy, we would probably run out of basics, like food, etc.”
At the same, Dr Pambuccian emphasizes that the most important steps that can be currently taken to turn the tide of the pandemic are to practice social distancing seriously and strictly. “Also, various political and social measures have to be taken: there are many categories of people for which 'social distancing' is meaningless: homeless people, inmates in jails and prisons. Something has to be done about these, but it requires a lot of political will and maybe resources. Nonviolent offenders should be released from jails and prisons, and if they have nowhere to go, try to find a solution for them. The same thing for homeless people,” he told MEAWW.