Author: Theresa Sokol, epidemiology manager
When a case of an infectious disease such as measles is confirmed in Louisiana, the epidemiologists in the Louisiana Department of Health’s Infectious Disease Epidemiology Program act as disease detectives to track the causes and consequences of these diseases.
The Program studies the spread of infectious diseases in the community and carries out or coordinates programs that prevent the spread of communicable diseases. With incidents such as the measles case in a traveler from the United Kingdom that was discovered in New Orleans in April 2018, an epidemiological investigation is done.
Measles is spread by airborne transmission. In other words, little particles can transmit the infection from people who have the disease to others. However, there are a number of other routes of transmission for diseases, such as:
- · Droplet, or infections that are spread through respiratory droplets, such as Pertussis (Whooping Cough). This transmission route differs from airborne transmission as someone would need to be much closer to the infected person to be exposed.
- · Fecal/Oral, or infections such as E. coli.
- · Waterborne, or infections that are spread through water.
- · Vector borne, or infections that are spread through vectors such as mosquitos, ticks, etc.
- · Blood borne, or infections that are spread through blood.
- · Sexual Transmission
There are a number of steps undertaken when a highly transmissible infectious disease is confirmed. This begins with an interview of the known patients.
Using the recent measles case in New Orleans as an example, our team interviewed the patient and fellow traveler to determine how they travelled, where they went, what restaurants they visited, and what health care facilities they sought treatment.
For a patient that traveled by air, our epidemiology team works with the Centers for Disease Control and Prevention to determine who was on the plane with the patient or who traveled in a taxi used by the patient. We then try and contact any other travelers who were in close contact with the patient.
It is interesting to note that for an air traveler with the measles, the CDC guidelines are to identify people in seats no further away than five rows in front and five behind. People seated further away than this are not considered to be at risk for exposure.
If a patient visited a restaurant or an event, we might work with the eatery to determine who else ate there at the same time and in proximity to the sick diner. We might also use reservations and credit card recipients to identify others who may have been exposed to the patient.
In the case of someone who attended a public event, we work with the event organizers to learn of others who attended and who may have been seated near the patient. Much the same process is used if it is determined the patient was in other social settings retail stores or other public venues. Depending on the nature of the investigation, we might also contact news media outlets to assist.
When our investigation leads us to others who were exposed to the infected patient, we monitor those people for the duration of the diseases’ incubation period. If no one else develops symptoms by then, it means they are not going to develop the disease. If symptoms do present, infected individuals are isolated, testing is done and the investigative process continues to see if other exposures occurred.
If it appears that an outbreak is a possibility, the health department might also recommend that others who are at risk get vaccinated to keep the disease from spreading. This was the case in 2017 when there was an outbreak of the mumps on the LSU campus in Baton Rouge.
Much like the police investigate a crime; our team looks for clues that help us determine the extent of the exposure and the risk to the community – all with the goal of limiting or eliminating the risk to others.
The investigation is considered closed when it is determined that no new cases are occurring.
For less transmissible diseases, such as mumps, or more infectious diseases that affect a higher portion of the population, such as the flu (which may infected up to 10 percent of the population), the focus is on educating the public. Efforts are made to encourage people to get vaccinated, surveillance is done and information is added to national reports.
Many diseases have been eradicated through the use of vaccines. For example, the last endemic case of measles in Louisiana was in 1996. To prevent future outbreaks, educate yourself and others on ways to protect yourself from infectious diseases.
For more information about Infectious Disease Epidemiology, click here.
For common questions related to infectious disease, click here.