Welcome to the iCover blog pages . The topic of our discussion today is the so-called. zero patients are the people with whom epidemics begin. The problem of accurate and early identification of “patient zero” is extremely important for world medicine. Having information about the first virus carrier, one can trace the path of the spread of the infection, find out its origin, and develop the most effective methods of combating the disease. The first ever software algorithm to detect patient zero with a high degree of accuracy was developed in Croatia in 2015. We will focus on the phenomenon of patient zero, the strengths and weaknesses of the proposed method in this article.
Zero patients who made history
In order to get some idea of the phenomenon under consideration, for a while, let us turn to history, which has preserved for us a number of classic examples.
If we can talk about the rating of zero patients, who are notorious for their disease, then perhaps the place of the leader in history can be awarded to Mary Mallon of New York State, better known at the time under the pseudonym Typhoid Mary. As the first healthy carrier of typhoid fever in the first half of the 20th century to be identified later on the American continent, Mary completely denied her attitude to the rapidly spreading disease.
Irish by birth, Mary Mallon moved to the United States in 1884. Mary’s Way, a first-class cook who worked from 1900 to 1907 in organizations and private households, was marked by a series of cases of typhoid fever in almost all places of her temporary stay. At the same time, in a number of cases “on duty” Mary was charged with caring for the sick, whom she had infected. Three of the 47 infected Mary patients did not survive. The first to establish a logical connection between Mary and the periodic outbreaks of typhoid that followed her was George Soper, who specializes in sanitary prevention. After another such outbreak in 1906, Soper, distinguished by scrupulousness and manic meticulousness, undertook to examine Miss Mallon’s “track record” and came to the conclusion that she was the source of the problems that befell New York State since her inception. Mary herself vehemently denied any involvement in the disease and firmly refused Soper’s insistent offers to undergo a full medical examination.
Perhaps Mary Mallon would have continued on her way, if not for the persistence of Soper, who managed to bring the police into the case. Compulsory examination in the clinic revealed the causative agent of the disease in the body of typhoid Mary, which confirmed the guesses of George Soper. Based on the results of the examination, the patient was admitted to a hospital on the islet of North Brother, where she was destined to spend three years in quarantine. According to the results of the tests, passed through the indicated period, Mary Mallon was found healthy and released under an oath promise that she will not work in the kitchen anywhere and under any circumstances. Having moved to the continent, Typhoid Mary got a job as a laundress for a meager fee, which she did until 1915. The next position, as you might guess, was the position of a cook at Sloane Women’s Hospital, where Mary was admitted, but under a different name. During her presence there, our zero patient expanded her track record with 25 more cases, one of whom died. After the fraud was exposed, Typhoid Mary was again escorted to North Brother Island for life in quarantine, where she died at the age of 69 in 1938. An autopsy revealed that the causative agent of the disease was the bacteria Salmonella typhi, found in Mallon’s gallbladder. PS Mary Mallon was born completely healthy, despite the fact that her mother had typhoid fever during pregnancy.
SARS, SARS, severe acute respiratory syndrome, atypical pneumonia
These names are one of the surviving and recovered zero patients, Huan Xingchu, a native of Foshan, Guangdong province. Like Mallon, Sinchu worked as a cook after being infected with the virus. From the moment Huang felt the first clear signs of SARS, the pandemic has spread across 29 countries and killed 750 people. The opinions of experts on how SARS is transmitted are divided. Often of them insist on the contact method of transmission of the virus, some argue that SARS, like the flu we know, is transmitted by airborne droplets, which largely explains the rate of spread of the disease. According to the authoritative opinion of the majority, the source of infection for patient zero was the meat of the civet, a predatory mammal belonging to the Vivver family – a traditional food of the inhabitants of southern China. While in Hong Kong and Singapore, the chain of transmission of the disease was restored, in China, where the bulk of the sick is concentrated in Beijing and Gundong province, experts could not track the path of infection.
Patient zero, who unwittingly opened Pandora’s box – Ebola, which killed 7,800 people, was two-year-old Emil Ouamouno from the small village of Meljandu in southeastern Guinea. As the group of researchers found out, on December 2, 2013, the baby played with the hollow of a tree where bats nest. Arriving home, the child felt intense fever and died four days later. The next victims and carriers of Ebola were three women who prepared the body for burial. Philomena, Emil’s sister, did not escape the sad fate. As a result, of all family members, including mother, grandmother and father, only the head of the family, Etienne Ouamouno, has survived to date. An expedition from the Robert Koch Institute (Berlin) found that the infection was caused by an insectivorous bat living in an ill-fated tree trunk. It is characteristic that a large hollow in a tree burned down by a lightning strike immediately after the outbreak of the epidemic is a favorite place for the kids of the whole village to play, but Emil was destined to become patient zero. Modern research has proven that Ebola is of animal origin (zoonosis). In particular, bats, pigs, monkeys fall into the category of dangerous to humans. The largest outbreak of Ebola was recorded in West Africa in 2014 and continues to this day.
The program will help you find a zero patient
Research aimed at finding and accurately identifying patient zero has long been in the focus of attention of scientists from leading laboratories in the world. An algorithm to achieve such a goal with a high degree of accuracy was developed in Croatia by a group of specialists from various fields. Due to the minimal set of theoretical tools available to the research group, in order to develop an effective search model, it was necessary to collect and then subject to analytical software processing a colossal array of statistical data. As a result, the scientists were able to identify the patterns that formed the basis for the model of the proposed algorithm for finding a zero patient. Testing the effectiveness of the algorithm on real statistical data has demonstrated a high degree of accuracy in determining the starting point of the epidemic in most of the cases considered. To determine the target, the algorithm builds a network of nodes that identify infected and healthy people in the epidemic area. The resulting network is digitally processed using analytical and Monte Carlo estimation methods. The result of the calculations makes it possible to obtain a “probability map” accurate to each person-node. After finding the node with a probability close to 100%, the software search for the zero patient ends. The task is recognized as solved.
Despite the convincingness of the search results for most of the analyzed cases, the developed algorithm has its limitations. So, for example, it is possible to identify several zero patients at once. In such cases, making a final decision requires the involvement of the potential of additional analytical tools and the personal involvement of a group specialist. In the process of evaluating the effectiveness of the algorithm on real data, it was noticed that its accuracy is the higher, the greater the speed and area of the epidemic. And, on the contrary, the application of the method on a small area with a relatively small number of people living in the territory covered by the epidemic, after a fairly long time after its start, often gave a result close to 100% for each of its inhabitants. Despite the considered limitations, the method proposed by Croatian scientists is currently the only one that allows in most cases to accurately identify the zero patient and determine the localization of the epidemic. Scientists are convinced that the considered algorithm may also be effective in virtual space, where computer virus epidemics develop according to a similar scenario.