Emerging infections are a recurring phenomenon. SARS-CoV-2 virus is just the latest example. Most of these emerging infections are zoonotic, meaning they crossed from animals to humans. HIV, a blood-borne and sexually transmitted infection, crossed from primates into humans. SARS, the original, crossed from bats probably via civets, a cat-like creature. MERS, which still causes sporadic cases, is transmitted from camels to humans. Ebola probably originated in bats or non-human primates, and it can be passed from one animal species to another. Influenza (whose likely original hosts are water birds and other avian species) has an impressive range of host species, including avian, porcine, and human, among others. The fragmented structure of the influenza RNA makes it especially facile at sorting and re-combining its genome into new varieties.
SARS-CoV-2 has rightly commanded everyone’s attention right now, as the COVID-19 pandemic it has caused is raging around the world. Before the first SARS outbreak in late 2002, caused by a related but distinct virus, the coronaviruses known to infect humans caused relatively mild disease, literally the common cold. But the SARS virus was different, as enshrined in its name, Severe Acute Respiratory Syndrome. The virus originated in southern China and went on to reach 26 countries, cause more than 8,000 illnesses and 774 deaths before it was brought under control. Fortunately for the U.S., only eight individuals in this country, all of whom had traveled to other parts of the world, were diagnosed with SARS through 2003.
The danger to humans (or any other species) of an emerging virus rests, among other things, in three properties:
- Infectivity, or, what dose of viral particles are needed to cause infection.
- Transmissibility, or how readily transmitted is the virus from one individual to another.
- Severity, or what is the spectrum of illness, from asymptomatic to lethal that the virus causes.
This, in turn, may be related to the original inoculum and depends on many host factors, including immunity from related, previous infections.
Many zoonotic infections do not result in a virus that can be readily transmitted among different members of the new host species. Unfortunately, the new SARS-CoV-2 is highly transmissible among humans via the respiratory route, and it falls somewhere between the lethality of influenza (0.1 percent) and SARS (almost 10 percent), perhaps at one percent overall as a ballpark. The number of severely ill patients who die will be a function of the age profile of the infected population, presence of chronic disease, genetic and perhaps other attributes of the patients, and quality of care available at the time of illness. This is part of the rationale for physical distancing, to slow the spread of infection to the point where hospitals will not be faced with larger numbers of sick patients than they can properly treat. The actual case fatality rate will depend on knowing the full extent of spread of SARS-CoV-2 in the community, including asymptomatic individuals, which is not established at this time.
While we cannot yet predict the emergence of a specific, new virus, scientists have identified properties of viruses that make them of graver concern, and coronavirus was put on the list of worrisome organisms a few years ago. In general, a number of factors play a part in fostering emerging infection, including urbanization, size and proximity of animal populations, opportunities for human-animal interactions, travel, mass gatherings, climate change, population displacement, and humanitarian disasters. Here, I will just say a few more words about cities and travel.
Approximately 55 percent of the world’s population currently live in cities, and the proportion is projected to exceed two-thirds by 2050. In 1990, only ten cities in the world had more than 10 million inhabitants. Now there are more than thirty such megacities, and the number is expected to reach 43 by 2030. Most of this urban growth is occurring in low latitude (tropics and subtropics) and low- or middle-income countries, a setting where many infectious organisms can thrive and spread. While cities supply many benefits to many people efficiently, they feature densely concentrated populations. The more densely packed and highly interactive a population, the more readily a respiratory virus, such as influenza or SARS-CoV-2 can reach a new person to infect.
The ease and accessibility of travel, at least in normal times, also contributes to the rapid and wide-ranging spread of viruses. Once you are able to get back on an airplane, you will be able to reach anywhere in the world within a day, and a recently infected, asymptomatic traveler can bring a deadly virus from virtually anywhere in the world to the United States in the same span of time.
As must now be evident to everyone, the world is ill-prepared to cope with major pandemics. After we overcome COVID-19, and we will overcome it, we must not ignore what it will take to be better prepared for the future: political will, financial resources, capacity building, scientific knowledge and social trust.
Political will: We need the political will and commitment to collaborate effectively across nation-states and among the government, corporate and nonprofit entities required to respond in these types of health crises. The U.S. has a long history of providing a measure of financial support and then largely ignoring the World Health Organization. Maybe it is time to start paying more attention. Global threats can best be met through a concerted effort involving every country willing and able to contribute.
Financial resources: Government, corporate and philanthropic entities should put forward, over the long term, the necessary resources for research, preparedness, containment and treatment efforts. The huge economic cost of the COVID-19 pandemic demonstrates why investment in preparedness is a relatively cheap insurance policy. Our public health and health care systems struggle financially in the best of times. When crisis strikes, they may be unable to cope. Here in the Silicon Valley, it is great to see philanthropy stepping in to help. Local community foundations are raising funds to expand local response efforts and the Chan Zuckerberg Initiative has enabled UCSF and Stanford to significantly expand their testing capabilities.
Capacity building: In this crisis we are witnessing health care and public health systems stressed beyond capacity. The frontline health-care providers, in this country and across the globe, deserve the protective gear, equipment, supplies and other resources they need to protect themselves and to care for those stricken in the pandemic. Private funders, including the Robert Wood Johnson Foundation and Kaiser Permanente are funding the CDC Foundation to increase our local public health departments’ ability to respond.
Scientific knowledge: Accurate information and evidence is critical if we intend to combat current and future threats. I applaud the Bill & Melinda Gates Foundation, Wellcome Trust and MasterCard for committing $125 million to speed the development of and access to COVID-19 treatments.
Social trust: Public safety depends on people’s ability to access and trust reliable and accurate information about health risks. A recent press release from the National Academies of Science, Engineering and Medicine underscored this point. “It is imperative that evidence-based information from expert sources be freely shared in order to counter the spread of rumors, misinformation, and uninformed speculation.”
It is a privilege to work for an organization such as the Gordon and Betty Moore Foundation, whose board encouraged me to take up the chairmanship of the National Academies Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats. Through that neutral forum, we are convening experts on a moment’s notice to provide scientific and technical advice to the White House Office of Science and Technology Policy and Department of Health and Human Services.
I hope this committee will also serve as a vehicle to investigate some of the critical longer-term issues, such as devising better predictive models for emerging diseases. The current crisis highlights the extraordinary potential for solutions such as a universal influenza vaccine that would provide safe, effective and long-lasting protection against all strains of the influenza virus. Over time, influenza has been the most regularly re-emerging pathogen, and influenza kills hundreds of thousands around the globe every year.
The conditions that led to COVID-19 will persist when this crisis passes. Government, businesses, philanthropy and our health care systems would be wise to design and fund global solutions that are effective and equitable. Science and technology, along with financial investment and the political will that undergirds it, can help us be better prepared for the next emerging disease.