An excerpt from Outbreaks and Pandemics: The Life of a Disease Detective.

The importance of disease detectives in solving and controlling outbreaks and pandemics must be recognized. We are the backbone of our public health system. We are scientifically savvy, inquisitive, detail-oriented, and able to follow the data wherever it leads, hopefully to answers and solutions to public health problems. Disease detectives are important in characterizing diseases in terms of defining risk factors for illness and establishing prevention measures to mitigate infections and deaths. We provide health care professionals with epidemic curves and future projections for outbreaks and pandemics based on typical human behaviors. We are able to characterize the mode of transmission of pandemic microbes, such as foodborne, waterborne, sexually transmitted, respiratory droplet, and person-to-person contact. Disease detectives are essential to developing effective interventions to reduce infections, such as chlorinating water, thoroughly cooking and irradiating foods, following safer sexual practices, wearing masks in public, thorough handwashing, and social distancing. In some cases, we put our own lives at risk in order to investigate outbreaks, especially those of unknown origin or emerging pathogens. In future pandemics, we must applaud and support these disease detectives, whose primary aims are to respond to epidemics and pandemics, prevent disease, and save lives.

John Snow, the most famous epidemiologist or disease detective in history, was able to determine that contaminated water from the Broad Street pump in London was the primary source of the cholera epidemic in 1854 and that removing the handle off the pump was the public health intervention to end the epidemic. Walter Reed was able to determine that mosquito bites were the primary route of transmission for the Yellow Fever pandemic in Cuba in 1901. In the early 1980s, epidemiologists at the CDC, along with doctors in California and New York, determined that the new immunodeficiency found in homosexual men was likely caused by a sexually transmitted agent yet to be identified. Once it was determined that the primary mode of transmission was sexual activity, safe sex using latex condoms could be used to reduce the risk of transmission even before the causative agent was identified. Smallpox ravaged the world for over three thousand years until Edward Jenner discovered that exposure to cowpox protected against smallpox infection, which led to the eradication of one of the greatest scourges of all time. Tuberculosis, or consumption, is a well-known respiratory disease that causes epidemics across the world. It was Robert Koch, in 1882, who discovered the bacterial agent which causes tuberculosis, and which subsequently led to the development of the BCG vaccination and the development of effective antibiotics. Ignaz Semmelweis is known as the father of hospital infection control, but other disease detectives such as Louis Pasteur, Robert Koch, and Joseph Lister also made important scientific discoveries that led to aseptic procedures such as universal hand disinfection in the hospital setting and the sterilization of medical and surgical equipment. William Foege, a former director of the CDC, devised a successful global strategy to eradicate smallpox. Peter Piot was able to figure out that Ebola in Africa, which causes severe internal bleeding and fever and has a high mortality rate, was spread by the reuse of unsterilized injection needles and contact with deceased persons who died from Ebola during funeral rituals, which included washing the body of the deceased. Jonas Salk and Albert Sabin were virologists who discovered safe and effective polio vaccines, leading us to the near-global eradication of the disease that paralyzed and disabled so many people. Dr. Paul Farmer, who died at the age of 62 while teaching at a medical school in Africa that he helped develop, strongly believed that health care was a fundamental right. All these scientists, doctors, and disease detectives played critical roles in helping us understand the transmission of diseases and how best to control diseases to minimize their impact on people and their communities. At least 10 of my former medical students and medical residents and infectious disease fellows have gone on to join the Epidemic Intelligence Service because of my influence and mentoring. These mentees have solved numerous outbreaks and had a meaningful impact in the fields of public health and medicine. My recruitment and contribution to the development of the next generation of disease detectives has been a source of great pride for me.

Vaccines are the most important public health measure for controlling over one hundred different infectious diseases. Before we had effective vaccines for COVID-19, epidemiologists were able to mitigate infections by employing the wearing of masks, social distancing, and quarantine. Once it was determined that Yellow Fever, West Nile, Malaria, Zika, Dengue Fever, and Chikungunya were mosquito-borne infections, control measures such as the elimination of mosquitoes and their breeding sites, and the prevention of mosquito bites using bed nets, pesticides, insecticides, and insect repellents, were used to reduce the risk of acquiring infection. The control of foodborne infections was greatly improved by adequately cooking high-risk foods, such as ground meats and eggs, the pasteurization of milk and fruit juice products, and the irradiation of spices. Similarly, waterborne diseases, such as cholera, E. coli, and typhoid fever, were controlled by water chlorination. As a result of hard work by disease detectives over the past 75 years, we have seen global improvement in life expectancy and a reduction in child and maternal mortality, and a reduction in numerous infectious diseases. Vaccine-preventable diseases have been the most substantial improvement in global health.

Now and in the future, disease detectives will remain extremely important for discovering and controlling new and emerging infections. Throughout history, human populations have been repeatedly challenged by pandemics. Given current events and trends, such as ongoing wars and refugees in resource-limited countries, the deforestation of our global rain forests, impact of global warming, migration of people away from cities to rural and mountainous areas, and increased natural disasters, animals, which harbor deadly viral pathogens, are likely to be brought into more frequent contact with human populations. Virus reservoirs in bats are likely of the greatest concern because they have been previously linked to Ebola, SARS-CoV-1, and COVID-19 infections in humans. There has always been a constant battle between our human existence and various opportunistic microbes, with respiratory viruses being the greatest threat to our continued existence and the continuation of human life on Earth.

The past several decades have been an extremely challenging time to be working in public health and medicine. Disease detectives have worked tirelessly in responding to infectious disease outbreaks and pandemics. I got to bear witness to both the HIV/AIDS and COVID-19 pandemics during my career, which had a tremendous impact on doctors, disease detectives, and other health care providers. We chose these careers to save lives and prevent illnesses, which is extremely rewarding and noble, but the HIV/AIDS and the COVID-19 pandemics, by causing millions of deaths, have brought us to our knees with their staggering impact on our world, the global economy, our lives, and how we interact with people. Despite these feelings of pessimism and defeat, we must continue to endure and learn to meet new public health challenges as they arise; we must continue to march forward in our well-worn shoe leather, because new outbreaks and pandemic battles are on the horizon, which we must combat and win to save humanity from extinction.

Nicholas A. Daniels is an internal medicine physician and author of Outbreaks and Pandemics: The Life of a Disease Detective.