American Ward at Fourth Scottish General Hospital, where most patients are influenza cases, in November 1918.
Universal History Archive/Universal Images Group via Getty Images
December 31, 2020 7:00 AM EST

“We were leaden-footed for weeks, to the point where each step meant a determined effort,” Miss Goring recalled. “It also was very difficult to remember any simple thing, even for five minutes.”

Miss Goring was describing the period of her convalescence after the 1918 flu pandemic, which she lived through in her native South Africa. Her memories form part of a collection published by South African historian Howard Phillips on the centenary of that disaster. It’s not the only one. Another collection published around the same time by New Zealand historian Geoffrey Rice is also littered with references to long-term symptoms of that flu—from “loss of muscular energy” to “nervous complications.” Some convalescents, recalled a Dr. Jamieson who worked at a hospital in Nelson, on New Zealand’s South Island, “passed through a period of apathy and depression,” or experienced tremor, restlessness, or sleeplessness.

What’s striking about reading these accounts ten months into a new pandemic, is the historical echo they provide of “Long Covid”—that mysterious affliction, or afflictions, that dogs some patients who were infected with the SARS-CoV-2 virus long after any initial symptoms have subsided, and apparently long after the virus has left their body. “Day 163 post Covid,” tweeted one Long Covid sufferer on Sept. 16. “I managed to walk for 20 mins without chest pain while keeping my heart rate below 120.”

One definition of Long Covid is “not recovering [for] several weeks or months following the start of symptoms that were suggestive of Covid, whether you were tested or not.” It’s an unavoidably woolly definition, until research elucidates the various post-COVID-19 syndromes that Long Covid almost certainly comprises. But in the meantime, it does the job of giving sufferers a label, so that they are more likely to be taken seriously and treated—to the extent that medicine has any treatment to offer them—and which recognises that the the virus can cause chronic symptoms that are distinct from the indirect impact on health of the pandemic’s social or economic fallout.

Research into Long Covid is getting underway—belatedly, because some sufferers were never hospitalized, not having experienced the severe respiratory symptoms that can characterise the acute disease—but for now there are more questions about it than answers. Nobody knows what proportion of those infected with the virus experience lingering symptoms, for example, and the bewildering diversity of those symptoms is only now becoming apparent. Profound fatigue is probably the most common, but others include breathlessness, aches, palpitations, rashes, and pins and needles. No tissue or organ seems to be spared—something that comes as no surprise to Debby van Riel.

A virologist at Erasmus University in Rotterdam, the Netherlands, van Riel has spent years studying how flu causes ravages beyond the respiratory tract. She has done so in human cells grown in a dish, in animal models and in patients—trying to capture, from the different angles these offer, the complex cascade of biochemical events that infection with various subtypes of the influenza A virus sets off in the body’s tissues.

Her subjects have included H5N1, the aggressive “bird” flu that—until last year—was considered a leading candidate for the cause of the next pandemic, the H1N1 “swine” flu that caused the most recent flu pandemic, in 2009, and the mother of them all, the virus that caused the so-called “Spanish” flu pandemic of 1918. Earlier this year, van Riel switched her attention to SARS-CoV-2, the virus that causes COVID-19, and saw that—though it behaves differently from flu—it too has effects far beyond the respiratory tract. “At least in its severe form, we should consider COVID-19 a systemic disease,” she says—something that is also true of flu.

Given these similarities, perhaps history can offer us some insights into what to expect from Long Covid. “The incapacity caused by the flu and its after-effects seriously affected the country’s economy for some time,” wrote Phillips in 1990, in Black October, his comprehensive study of the 1918 epidemic in South Africa. In what is now Tanzania, to the north, post-viral syndrome has been blamed for triggering the worst famine in a century—the so-called “famine of corms”—after debilitating lethargy prevented flu survivors from planting when the rains came at the end of 1918. “Agriculture suffered particular disruption because, not only did the epidemic coincide with the planting season in some parts of the country, but in others it came at the time for harvesting and sheep-shearing.” Kathleen Brant, who lived on a farm in Taranaki, New Zealand, told Rice, the historian, about the “legion” problems farmers in her district encountered following the pandemic, even though all patients survived: “The effects of loss of production were felt for a long time.”

A century ago, a greater proportion of the world’s economy was derived from agriculture, but it wasn’t only agriculture that was affected. Phillips recounts the case of a train driver who was involved in an accident in 1919 who later explained that he suffered a blackout while at the controls: “He claimed that this was the after-effect of an attack of Spanish flu the previous year, which had left him ‘never… quite the same since.’” Similar reports came from all over the world. British doctors noted that cases of nervous disorders including “melancholia”—what we would call depression—showed a marked increase in 1919 and 1920. Schoolteachers lamented that it would take their pupils months or years to recover lost ground.

The trouble with discussing the 1918 pandemic is that it overlapped with World War I, making it difficult if not impossible to determine the relative contributions of the two disasters to any subsequent wave of lethargy or mental illness (the pandemic – like today’s – might also have had indirect effects on health, due to the bereavement and social upheaval it brought in its wake). Studies from countries that were neutral in the war, such as Norway, are therefore invaluable, since they afford a glimpse of the impact of the pandemic that is uncomplicated by that of the war. Norwegian demographer Svenn-Erik Mamelund provided such evidence when he combed the records of psychiatric institutions in his country to show that the average number of admissions showed a seven-fold increase in each of the six years following the pandemic, compared to earlier, non-pandemic years.

As precious as such findings are, we need to be cautious in interpreting them. For one thing, there’s no way of demonstrating, retrospectively, a causal link between the flu and the psychiatric illnesses those patients were suffering from. For another, the taboos around mental illness, as strong if not stronger then than now, mean the numbers may not accurately reflect the extent of the phenomenon. Although it’s almost impossible to gauge how common “Long Flu” was in the years after 1918, the working assumption is that it affected only a small proportion of survivors—and this is also the working assumption regarding Long Covid, on the basis of still-sketchy data.

Nevertheless, given the tens of millions who have already been infected by SARS-CoV-2, even a small minority could amount to substantial misery, not to mention social and economic fallout—as it did 100 years ago. That’s reason enough, says psychiatrist Simon Wessely of King’s College London, “to investigate the Long Covid cases with the same rigour and vigour that studies like PHOSP-COVID are investigating the hospitalised cases.”

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