Sunday 4 January 2015

Tracking Suspected Ebola Cases

One of the problems in this epidemic so far has been the lack of good surveillance data that can identify Ebola cases and potential transmission events. Epidemiologists might say that if we had good data, it would be easier to dispense teams of prevention workers to hot spots and stop Ebola transmission.  To understand the challenges of collecting good surveillance data in this environment, you have to understand how cases are tracked through the system.  This process has become clearer (but probably imperfectly clear) to me while we have been here in Freetown. The procedures that are being used here are the same ones used everywhere when outbreaks occur, and these procedures can work really well, as we saw they did in Nigeria.  However, the lack of coordination, a strong government and health system has created obstacles to the procedures working as they should.

If someone suspects a case of Ebola in their community or is a suspected case themselves, they are advised to call the national hotline (117) in Freetown.  I've read that only about three percent of these calls trigger a household visit for a suspected case of Ebola.  Once a household visit is triggered, a surveillance team goes to the house in an ambulance wearing full PPE (personal protective equipment), which I imagine is a bit scary.  At the house, the surveillance team then evaluates whether the person meets the case definition for Ebola (http://www.cdc.gov/vhf/ebola/hcp/case-definition.html):
  1. Fever or symptoms, including severe headache, fatigue, muscle pain, vomiting, diarrhea, abdominal pain, or unexplained hemorrhage; and 
  2. An epidemiologic risk factor within the 21 days before the onset of symptoms, including but not limited to exposure to: contact with body fluids of someone with Ebola, a dead body from Ebola, or a person who had symptomatic Ebola. 
If the person meets the case definition, the surveillance team washes the area with chlorine and then takes the person to a holding center where they await the results of a laboratory test for Ebola and malaria.  Today we heard from MSF that 48 hours is the fastest they can get an Ebola test result back from their laboratory (and this is probably the fastest in the country).  So for two days the person who possibly has Ebola is sitting in the holding center waiting for the lab result with all other cases that could possibly be Ebola.  If there are good and rapid lab services, people who only have malaria get identified and out quickly, reducing the chances they get Ebola.  However, if the lab services are not good, or if the person's malaria test was negative, the person waits longer, increasing possible exposure to Ebola at the holding center.  If the Ebola test comes back negative, the person is sent back home. However, it is possible that the person had Ebola all along but needed a couple more days before the test turned positive (remember there is a lag time between getting the virus and having a positive Ebola test because you have to be symptomatic). It is also possible that the person contracted Ebola while at the holding center. So, really, they will need to test again.  Then anyone who returns home from a holding center is supposed to be monitored daily and quarantined for 21 days.

Once a person has been confirmed positive with an Ebola laboratory test, that person provides a list of all people they have had physical contact with in the past 3 weeks (physical contact includes sharing the same room/bed, caring for a patient, touching body fluids, or closely participating in a burial www.ebolaalert.org/SOPct.pdf).  There is a team of contact tracers (in Sierra Leone many are volunteer medical students) who elicit and then trace the infected person's contacts.  All of these contacts are then monitored daily for 21 days for fever and symptoms. In addition, the contacts are quarantined for 21 days and given food, buckets, gloves and bleach. There have been some concerns mentioned to us that quarantined households have not been given enough supplies or food.  During the daily visits, the quarantined contacts are asked if there are others in their households have become sick. If anyone falls ill while under quarantine, they are taken to a holding center for the Ebola test.

A person with a positive Ebola test goes from a holding center to a treatment unit, if there are beds available. In the beginning of this epidemic, even people who had a positive Ebola test could not get a treatment bed because there were so few in the country.  People would stay at home and infect their household members.  Fewer people were reporting suspected cases to the hotline because they knew there would be no treatment beds for them.  Now there are a lot more treatment centers in Sierra Leone, which leads to improved surveillance and contact tracing. But no one knows the effect that those early days had on the response. Some people fear that people don't trust the hotline anymore. The other problem is that treatment centers are still not everywhere in the country.  A sick person might have to travel many hours to then wait for a laboratory test or a treatment bed.

Who is providing all of these services? The government of Sierra Leone is taking all the help it can get. This means that in the contact tracers might be hired by the WHO, but the holding center is run by MSF or another organization.  The burial teams are being largely run by the Red Cross. There is no one entity coordinating all these agencies, and therefore there is no one entity tracking identified or suspected cases.   Which brings me back to my point about surveillance.. without coordination it's nearly impossible to track people through the system, creating a huge barrier to precise data collection and monitoring.

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