One of the craziest concepts that a lot of us have been forced to be familiar with lately is asymptomatic carriers. I know we’ve all heard the term and most people understand what it means. Asymptomatic means a person does not show symptoms while they are infected. This concept applies to many diseases that have been a scourge to human populations across history. Diseases that have been confirmed as being capable of having asymptomatic carriers range from typhoid, HIV, influenza, and many more including SARS. Because of the nature of asymptomatic carriers there are some misconceptions and it is very difficult to study the spread from person to person. In the following some history of asymptomatic carriers and the possible meaning for today is discussed.
Famous Occurrences in History
Throughout history, all the way back to the ancients, it was widely understood that people infected with certain diseases are able to infect more people. Procedures have been put in place for thousands of years to curb the spread of disease. Most often, this was done through the use of quarantines and isolated hospital colonies. Infected peoples were placed in isolation until it was deemed safe, which wasn’t all that common. This is effective at slowing the spread of many diseases, but it rarely impedes the progression of infection totally.
In early Greece and Turkey during instances of great sickness like the plague, there were quarantines imposed on shipping vessels requiring 40 days sitting in the harbor before they were allowed to port. This was done to ensure the sailors would not spread disease once they were in port. However, there were still instances of disease transmission in cities with strong preventative procedures. This may have been because of disease vectors like rats or fleas spreading disease. Or these diseases may have been transferred by an asymptomatic carrier who spread the disease wherever they traveled.
It wasn’t until the 1910’s when an actual asymptomatic carrier was identified and isolated in the United States. The story has become an urban legend inflated to the likes of a tall tale. The first discovered asymptomatic carrier of typhoid fever in the United States was a woman named Mary Mallon. Mary has a very interesting story that altered the legal and ethical framework of law and procedures regarding public health.
In 1907, Mary was discovered working as a cook for many families and soldiers. At the time, germ theory and proper hand sanitation was not common among the public compared to medical communities. The idea that healthy people could transmit disease was highly uncommon even in the medical community. However, after a high percentage of the households she had cooked for over a period of five years had an occurrence of infection, medical experts became suspicious. Their suspicions were correct. Mary was a seemingly healthy person who could spread the disease to others. In fact, the total cases that were confirmed to be caused by Mary Mallon topped thirty-three infections with at least three deaths. Urban legends have greatly exaggerated this number, but the confirmed total is thirty-three.
Because of her condition she was initially quarantined on a hospitalized island outside New York City for 2 years and 11 months. Upon her release, the details of her condition were fully explained. The government explicitly forbade her from returning to work as a cook. After a couple year period of performing lesser paid work and falling on hard times, Mary once again became a cook. As expected, there were instances of typhoid at most of the places she worked during this period. She changed jobs often making it difficult for authorities to locate her. After a total of five years she was discovered and forcefully returned to the island where she would reside for nearly three decades until her passing.
Today’s medicine is incredibly advanced compared to practices in the early 1900’s. Our diagnosis procedures, quarantine methods and range of tools available make us far better equipped to deal with a newly discovered asymptomatic carrier than ever before. The idea that just a few carriers could maintain an epidemic is not nearly as probable as they were before the era of mass surveillance and effective diagnostic tools. However, asymptomatic carriers still pose a considerable threat.
Recently, the WHO has made some statements regarding COVID and the prevalence of asymptomatic carriers based on some preliminary data. As reported by Newtrals, Dr. Maria Van Kerkhove stated it “appears to be rare that an asymptomatic individual transmits onward.” This has been a very large point of concern because asymptomatic carriers would not be aware that they are spreading the disease and are therefore impossible to control unless they are already voluntarily quarantining. According to minimal data, it appears that there may be a reduced likelihood that “healthy carriers” can pass the disease as readily as cases with moderate or severe symptoms.