November 25, 2024
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Preventing future pandemics requires confronting the dangers of silent spread.
Targeted public health interventions are needed to reduce transmission from asymptomatic carriers. As with the coronavirus, when a pathogen spreads silently, it can cause more infections and deaths.
Bimrat Deniz/Getty Images
The obvious runny nose of a cold, or the fever and aches associated with the flu, are hallmarks of respiratory illness, along with its symptoms. Public health messages rely on these symptoms, urging people with symptoms to stay home and avoid others. That makes sense. Reduce the risk of one case becoming many.
But what happens when infection is not necessarily linked to symptoms? COVID-19 has shown that asymptomatic spread of disease can have devastating social consequences. Preventing future pandemics therefore requires greater investment in targeted public health interventions to reduce transmission, including transmission from healthy infected individuals.
In fact, asymptomatic infection is a sign that the novel coronavirus, which rapidly spread in Wuhan, China in early 2020, has become a global pandemic with more than 1 million deaths reported in the United States by May 2022. It was essential for the transition to The person can infect others before symptoms appear (presymptomatic stage) or even if no symptoms appear. A comparison of data from the early stages of the outbreak revealed that about half of those infected were asymptomatic. That would be good news if asymptomatic carriers were not contagious. But that wasn’t the case.
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On February 23, 2020, researchers from China, France, and the United States published a joint analysis of more than 450 new coronavirus infections in 93 cities in China. The analysis focused on the serial interval, or the time between someone showing symptoms and the time an infected person shows symptoms. Contrary to expectations, the analysis showed that the time between successive infections of the new coronavirus is often less than zero, meaning that symptoms appear before the infected person. These statistics were evidence of widespread presymptomatic infection. Public health experts have warned that efforts to contain the virus through symptom screening (such as tests for elevated body temperature and shortness of breath) are bound to fail and that “unprecedented measures” are needed to fight back. I tried to ring it.
The deadly effects of asymptomatic infection quickly arrived in the United States On March 10, 2020, the Skagit Valley Chorale gathered in a Seattle suburb for a rehearsal. Despite efforts to limit physical contact, within days it became clear that someone in the group had unknowingly infected others. In the end, 53 of the 61 participants were infected and two died. This superspreading phenomenon reveals that the new coronavirus can spread through the air even when there are no symptoms. However, the relevance of asymptomatic infection remains controversial. On June 8, 2020, a senior WHO official declared asymptomatic infection “very rare.” The pandemic was raging, and we were losing precious time to fight the silent spread. The consequences were severe. Anthony Fauci, head of the White House Coronavirus Task Force, said in August 2020: In some cases, it can be severe enough to cause death. ” Asymptomatic infection is a double-edged sword. Individual outcomes may be better, but silent spread may result in more infections and worse outcomes for the population.
What can be done to reduce asymptomatic transmission? Early responses to the pandemic included restrictions on gatherings and curfews. However, the unusual combination of severe and asymptomatic outcomes of the coronavirus has led various stakeholder groups to invest in unconventional approaches to reduce the risk of silent spread. These approaches include real-time risk assessments, rapid testing at scale, situational masking, and improving indoor air quality. Each of these plays complementary roles in reducing silent spread and, if deployed at scale, could become essential weapons in the ongoing fight against pathogens with pandemic potential.
In the absence of symptoms, real-time risk assessments leveraging outbreak models and disseminated through mobile-accessible dashboards can serve as predictive threats. These dashboards could provide mapped information on various infectious disease risks, such as the spike in coronavirus cases being reported in wastewater. People can then decide to avoid events where the risk exceeds an acceptable level. However, even if someone does attend an event, rapid testing on-site and the use of masks could limit transmission. This could have significant benefits, especially in nursing homes and long-term care facilities, which account for a disproportionate share of overall deaths from the coronavirus. Regardless of individual behavior, infrastructure investments in indoor air quality (through improved filtration, air turnover, and UV-C sterilization of upper rooms) can improve health outcomes.
Finally, we must commit significant resources to the development and effective distribution of vaccines in the United States and around the world, especially in developing countries. Billions of vaccine doses have been produced in just one year since the emergence of the coronavirus, an incredible demonstration of the power of basic research and public-private partnerships. However, producing a vaccine does not necessarily mean it will be injected into arms. Public health agencies need to improve their messaging to explain why individuals can benefit from vaccines, when they should get the vaccine (and boosters), and what each vaccine means. . In the case of the new coronavirus, mRNA vaccines have been shown to reduce the incidence of symptomatic illness by more than 90 percent. However, these vaccines do not protect against all infectious diseases. This means that vaccinated people can still get infected, test positive, and infect others, but the risk of severe outcomes is reduced. Masu. This is exactly the point. However, the fact that vaccines did not provide complete protection against infections (asymptomatic or not) not only against influenza and coronavirus, but also against preventable childhood diseases such as measles , has accelerated the spread of misinformation that threatens to reduce vaccine uptake.
It’s been nearly five years since the early warning signs of the novel coronavirus, which spread in Wuhan with asymptomatic transmission and soon to become a global pandemic, appeared. At the time, risks to public health and socio-economic stability seemed remote. Since then, scientists, public health experts, government agencies, and the biotechnology sector have developed a series of countermeasures to combat the dangers of silent spread, and the impact of silent spread of avian influenza in the wild and domestically. There is still work to be done, including identifying the animal. To reduce the continued burden of COVID-19, we need to build on this momentum with data-driven threat assessments, high-impact interventions (ranging from testing and air quality improvements), faster vaccine deployment, and increased support from doctors and public health agencies. It is essential to convert it into a more effective message. These actions will make the world better prepared to identify, prevent and respond to upcoming pandemic threats before it is too late.
This is an opinion and analysis article and the views expressed by the author are not necessarily those of the author. scientific american.
