Anyone who thought infectious diseases were being consigned to history has been shaken out of their complacency in the past two years by the emergence of the coronavirus pandemic.
While three non-communicable conditions — heart disease, stroke and chronic obstructive pulmonary disease — have long been the world’s top killers, the surging burden of Covid-19 is now running close behind. According to the World Health Organization, the virus has resulted in more than 220m cases of infection and more than 4.5m deaths.
It has also focused fresh attention on the dangerous spread of viruses and other pathogens around the world; highlighted the weaknesses of health systems everywhere; and revealed the blurred boundaries of cause, effect and interaction between communicable and non-communicable disease.
The pandemic has caused extraordinary economic and social disruption globally, closing schools and offices, sealing borders and limiting social contact. Governments with squeezed budgets have struggled to cope with the hardship and inequality that Covid-19 has exposed — and worsened.
Hans Kluge, European regional director of the WHO, who this month released findings of a Pan-European Commission on Health & Sustainable Development to learn the lessons of Covid-19, says: “We have all been taken by surprise. Health systems that we deemed very strong were overwhelmed. It is time to rethink preparedness.”
Some of this surprise stems from the fact that, for many years, communicable diseases were on the wane as a result of improved diets, reduced poverty, better sanitation and the introduction of innovative medicines and vaccines. Smallpox was eradicated; deaths caused by measles, malaria and meningitis sharply reduced; and more recent emerging infections, such as HIV, were brought under better control.
Even in lower-income countries, economic development and investment in healthcare systems have helped ease the relative impact of infections. But, paradoxically, such economic progress has helped create a “double burden” that includes various non-communicable conditions associated with longevity and “lifestyle”, such as diabetes.
Still, transmitted respiratory diseases have remained significant contributors to morbidity and mortality everywhere. Tuberculosis burdens poorer and more marginalised groups in richer, middle-income and developing countries. Other infections and variants have also appeared, such as Sars, Zika, chikungunya, MERS and Ebola.
Furthermore, the overuse of antibiotics in humans, animals and even plants, combined with poor manufacturing practices and hospital hygiene, has led to a surge in drug-resistant microbes. That is reducing the effectiveness of available treatments and risks outstripping the thin pipeline of new products in development.
However, no health condition has mobilised more action in recent years than Covid-19. It has been the most devastating outbreak since the great influenza pandemic of 1918, which levied a death toll estimated at 50m — more than were killed in the fighting during the first world war.
SARS-Cov2, the virus behind Covid-19, transmits rapidly and easily, and has continued to mutate, defying attempts to limit a spread that has been helped by intensifying globalisation. The most effective initial defensive tactics were barely changed from those used to tackle the plagues of centuries past: notably quarantine and isolation.
Yet, recent advances in science and technology have permitted a far more powerful response than would have been possible even a decade ago, when the last flu pandemic — which ultimately petered out with relatively few deaths — caused significant global disruption.
New vaccines, medicines and diagnostics have been developed in record time and widely distributed in richer countries. Mobile communication has allowed people to work and study remotely, and helped collect data to track the disease and identify optimal drugs to treat it.
But while progress has been made in tackling Covid-19, much less is understood about “long Covid” — the varied range of symptoms associated with the virus’s after-effects, experienced by a large share of those infected. There is not yet a diagnostic test, and there are competing theories on its mechanisms, leaving doctors and patients uncertain of how to respond.
One indicator, so far, is that many of those most affected have had underlying medical conditions, either non-communicable diseases such as diabetes, or precursors such as obesity.
Minimising the effect of the pandemic — and mitigating the impact of future outbreaks — pushes public health specialists including Martin McKee from the London School of Hygiene and Tropical Medicine to call for greater investment in supporting healthier lifestyles, such as efforts to curb tobacco use and poor-quality diets.
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He argues for the need to tackle underlying structural “social determinants of health”, which contribute to many diseases. These include addressing inequality and strengthening the resilience and inclusiveness of health systems, to redress imbalances.
McKee, who advised Kluge’s commission, also stresses the importance of “One Health” — considering the interactions between human, animal and plant health that contribute to the growing spread of infections between species. “We have to have a much more holistic approach to health, with One Health at its centre,” he says.
This month, more than 220 editors of medical journals argued that the world needs to step up its efforts in tackling climate change, which poses an existential threat to humanity through the risks of conflict, food insecurity and the spread of zoonotic disease between animals and people.
These themes were picked up by Mario Monti, the former prime minister of Italy, who chaired the Commission. He calls for new mechanisms, including a global health board under the auspices of the G20 group of mostly wealthy nations, to elevate the political focus on health, prioritise investment and increase accountability.
But the ambition of the recommendations, coupled with previous failures to heed the advice of pandemic postmortems, leaves many sceptical that they will gain momentum. Monti concedes that “policymakers have some chronic diseases” of their own: short-termism and short-sightedness — not thinking beyond their own electoral cycles or their own national boundaries.
But Monti points to parallels with the creation of the Financial Stability Board by central bankers in the wake of the 2008 financial crisis, and says the unprecedented focus of leaders on the pandemic presents a chance.
He says: “I’m optimistic. I think we are approaching a moment of discontinuity in the quality and seriousness of public policymaking. There is readiness and willingness to do something similar in health.”