Community Health Toolkit

New App Supporting Event-Based Surveillance for COVID-19

Over the past few weeks, the Medic Mobile team built a reference version of a COVID-19 Event-Based Surveillance App for use by Community Health Workers, CHW supervisors, and MoH Investigators.

The current version of this reference application is based off of design work the Medic Mobile team has done with the Ministry of Health in Kenya, CDC, KEMRI, and HJFMRI to develop and deploy a community-level, event-based surveillance system in two counties. The system was the first of its kind in Kenya and it is ready for reuse and scale in Kenya and countries with similar requirements to respond to COVID-19.

CHT System Features

This is a simple workflow that enables CHWs to use SMS to report signal codes for specific health threats to their supervisors for verification, which are then escalated to the sub-county for investigation and follow-up. This CHT reference application is designed to be flexible in nature and there is the potential to combine EBS with other CHT COVID-19 workflows, including, for example, Contact Tracing or COVID Self-Checks.

  1. No hardware costs, by leveraging personal devices in the hands of the CHWs, CHW supervisors and sub-county teams, as well as facility or county-owned computers/laptops
  2. Free-to-end-user interaction with centralized SMS billing and an existing short-code
  3. Simple and user-friendly SMS and mobile application design
  4. Scalable platform which can be sustained as a national platform in the future
  5. Built-in escalation mechanism to ensure timely response

Our application enables real-time reporting and visualization at multiple levels of the health system to inform decision-making related to COVID, including HRH and PPE allocation, planning for isolation centers, and adapting PHC protocols to maintain care.

Time-Sensitive Opportunity

For many countries around the world, now is the time to be planning early detection and surveillance interventions to try to mitigate the impact of COVID-19 through proactive identification and treatment of patients before the size of the case counts is too high to do so.

For partners interested in deploying Event-Based Surveillance using the CHT, we want to share some insights on this opportunity:

  1. Medic Mobile will support training for all CHWs, Supervisors, and Health Admins on COVID-19 signals and reporting procedures
  2. Additionally, Medic Mobile is working on building workflows on the CHT core framework to train CHWs remotely through a series of SMS instructions on the case definition, reporting role, and reporting process, as well as associated videos and images
  3. This app enables monitoring for COVID-19 signals via a signal ID sent to the MOH shortcode
  4. EBS allows for collaboration with existing partners with district-level coverage
  5. We focus on COVID-19 signal reporting now and can add additional signals codes later
  6. Our goal is to achieve the earliest possible detection of cases to minimize local transmission
  7. The hope is to achieve visibility into signals, reports, and investigations centrally

For more information on this COVID CHT use case, please refer to our CHT EBS documentation resource.

We’d love to hear from the members of our community. What do you think about Event-Based Surveillance in the community? What feedback or questions do you have for the team at Medic Mobile? We look forward to discussing this with you here!


That’s great news. We are starting to adopt this here in Zanzibar, where we support the Ministry of Health in their national CHV program. We think that community-based EBS can become an important pillar of an IDSR after COVID-19.

We already have CHVs working in some districts who are using a CHT app, but want to include CHVs from additional districts who don’t have smartphones. We are currently thinking about the best us of the tools:

  • For CHVs without smartphones, the situation seems pretty clear. A practical/implementation question is, how to setup the shortcode system. Does anybody have any experience with phone providers or middle men (I seem to remember someone mentioned you are collaborating with Afrifa’s Talking), what are expected turnaround times and costs?
  • For CHVs with smartphones, we could
    • Create new forms in the app, which would require close monitoring of data packages or reverse billing set up, and making sure they have a place where they can get connectivity at least once a day. For monitoring of data packages, an MDM with that functionality would be easiest, but we do not have that at the moment. An alternative approach might be to monitor “last synced” times and use some kind of cascade through district managers and supervisors. Reverse billing would probably be easiest, but we haven’t been able to set this up yet.
    • Use medic-collect; that way they we would have more usable and richer reporting, while still leveraging the more reliable SMS communication.
    • Use the same process as for CHVs without smartphone. The advantage would be simpler implementation.

One thing that is not so clear yet: if we follow a mixed approach, what will be the challenges harmonizing workflows and data as we go further up the reporting hierarchy? What is also not so clear yet is whether and how we need to adapt our user hierarchies.

I’d be interested what the experience so far is of folks who have already implemented something similar.

Hi @hhornung, indeed we are happy to provide you with all the information you require and support your work in Zanzibar.
We have been working with Africa is Talking to support in setting up and maintaining the shortcode platform. Unfortunately, they are currently not in Zanzibar but I am sure there are other options available in Zanzibar. Regarding costs and the turnaround time, it took approximately 1 week to have the shortcode active with AT. The cost also depends on the selected package, this information is available upon request. However, these two factors depend on the service provider and local settings.
I am happy to provide more information on this if required.

I will let my colleague @bernard to provide more information on the other issues.

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@hhornung the reference app in this post has been built using the app you already have some of the CHVs using, so your first option that involves adding the new forms to the app is very doable. In fact, all of the options you list are all valid. The uncertainty, as I understand it, is around how to manage billing if you were to go with the first approach and what the complexities of using a hybrid deployment are if you were to go with the other options.

You are right, the ideal solution to connectivity and billing challenges when using the app is to set up reverse billing which is done by white-listing the app URL by a Telco for internet connectivity. As you are probably aware, setting this up is a very Telco specific process that is usually not part of Telcos normal services. From your comment, it sounds like you have experience with that process and we would love to hear more about that experience.

Medic Collect is a viable option for users with smartphones where the desire is to have users submit reports via SMS and so is plain SMS. Where Africa’s Talking is not an available option, the use of Medic gateway may be the next best option. Medic Collect would then be configured to send the reports via phone number attached to the Medic Gateway. It would work the same way as in the case of the use of a short-code. To harmonize data for a CHV submitting reports via both Medic Collect and CHT app, the only requirement would be to ensure the phone numbers in CHV profiles are the correct ones. That way, the reports submitted via Medic Collect would be automatically added to their profile, using the phone numbers as the linking field.

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@hhornung I’m linking the pricing page for Africa’s Talking - You’ll find a pricing filter (by country) almost half-way down the page. They have coverage in Tanzania - do you use the same MNOs in Zanzibar?

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Thanks all for the helpful explanations. Regarding reverse billing, we are still trying to set this up, but haven’t been successful so far.

Africa’s Talking seems to be an interesting option. Here, the concerns are around pricing, scalability and robustness. We have a toll free number and closed user groups, so CHVs can send and receive SMS without additional cost. We could thus set up a phone as the SMS gateway. My questions here are:

  • Would this scale reasonably well for up to 2500 CHVs? I expect with Africa’s Talking, we wouldn’t have an issue here.
  • How robust would that be, if the phone is also used for different purposes and not always connected to the internet? We currently use the toll free number to receive support calls from CHVs and supervisors. And with intermittent internet connectivity here in Zanzibar we could have stretches without connectivity, so messsages might pile up in the queue.
    If we work with Africa’s Talking, how do we connect the service to the CHT server? Or would this also go through Medic gateway? (Please feel free to point me to documentation. I remember to have read about the integration, but couldn’t find the documentation on github)
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Would this scale reasonably? We have run a pilot with 400 CHVs with MOH Kenya using SMS and Medic Collect for close to 8 months now and while that number is not close to the 2500 you have indicated, there is no reason at this moment to think that it would not scale well. SMS deployments generally scale well. It is also worth mentioning that we are also working on a number of feature requests to be released soon that are informed by this pilot that will generally improve the app to support this even better.

On gateway robustness, unfortunately, it is encouraged that the phone being used as the gateway is not used for other purposes so that messages flow is not interfered with. It is also a requirement that it is connected to the internet as that is the only way messages are forwarded to the server and messages from the server are received by the gateway for forwarding to clients. One way we have worked around this in other setups is to ensure that the phone is loaded with cellular internet credits so that when there is no WiFi connectivity the gateway can fall back to using that. It may also be that the gateway is put in an office closer to a reliable connection as the gateway’s location does not affect the deployment.

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@hhornung here is the documentation to how set up Africa’s Talking

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Hi, Heiko – echoing others, I’d recommend deploying with AT if it’s available in Zanzibar.

Medic Gateway is a great option if AT isn’t available; I don’t think you’ll run into scaling issues with EBS given the expected frequency of use/messaging.

I’d also suggest the simplest possible implementation and onboarding approach across the national network, which is likely SMS for initial onboarding to reporting responsibilities and process, a phone call with supervisors for any Q&A, and SMS for all CHWs for reporting signals.


Thanks, Bernard for the pointer to the documentation, and Josh for the recommending AT and suggesting the simplest possible approach, which is definitely in line with our thinking, given that we try to deploy something as soon as possible. I’ll continue to post updates here as we talk to our ministry partners and make decisions about program and technology design.


Hi @hhornung, I also want to flag that we are having a working session on Monday, April 20th from 9-10:30am PST to discuss EBS design and requirements across different CHT deployments and it would be wonderful if you could join the conversation. Please let me know if you are interested and I’ll follow-up with additional information!


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HI @helenelizabeth, that would be great. I’d definitely like to participate! We had some internal conversations and were able to talk to our ministry partners, so some of the ideas are starting to get more concrete.


Wonderful! We will make sure that you are included on the invitation for Monday’s session and we look forward to working with you on this.