Thomas Eric Duncan, America's first Ebola fatality, went to a Dallas hospital twice in the days before he died.

The first time he arrived under his own power. The second time, when he was much sicker and more contagious, an ambulance took him in. He ended up exposing three people who rode in the ambulance with him to the virus.

Experts say that this second route, via Emergency Medical Service transport, is how future Ebola patients in the United States are likely to get to a hospital — and in the process, they will expose first responders and other patients to contagion risk. EMS organizations are already adapting, and they're getting support from private companies that make software for first-responders, including Edina's Open Inc.

Open is one of several companies nationally that sell mobile computer systems used to evaluate and record patient health information in the field, before arrival at hospitals. Open rolled out updates to its SafetyPAD system in October that allows the system to detect telltale signs of infectious disease risk and automatically send reports to supervisors, government officials, and public health agencies.

SafetyPAD's first foray into infectious disease monitoring came in 2006 with the arrival of the H1N1 flu virus, and it was expanded to include surveillance for such viral diseases as SARS and MERS. But the news of Ebola in the United States changed everything.

"When the gentleman in Dallas was diagnosed, we saw an exponential growth in our customers having a high level of concern," said Mike ­Vukovich, Open's founder.

SafetyPAD is a program that runs on a rugged tablet computer carried in an ambulance or fire truck. It prompts paramedics to ask specific questions to patients in the field, documents the answers and then analyzes the responses to see if follow-up questions are needed. Alerts for ­potential cases are automatically e-mailed out.

For Ebola, the system looks for key symptoms like high fever, vomiting, coughing blood or unexplained bruising. If those are present, the system will prompt the paramedic to ask whether the patient has traveled internationally in the past 30 days. If yes, what countries did the patient visit? Did the patient visit a hospital there? Did they encounter other feverish people?

"There are very straightforward questions you can ask a patient, and through the answers, you can expand the treatment or the incident if you need to," said Brian Schaeffer, assistant fire chief in Spokane, Wash., which uses the SafetyPAD system. If too many answers are positive, responders can don extra protective equipment and take steps to protect other patients.

Meanwhile, alerts about potential Ebola cases are sent to recipients back at headquarters, or in the hospital or the public health department. Such alerts are "HIPAA cleansed," Vukovich said, which means they can be viewed on smartphones or computers in public without risking exposure of patients' protected health information.

Of course, it might be tough to find a paramedic in America who doesn't already know about the risk of Ebola or the need to ask certain questions when confronted with a feverish patient in the field. But systems like SafetyPAD are designed to make sure every relevant question is asked and ensure uniformity in the responses.

"There are thousands of questions you can be asking in here," said Robert Ball, a supervisor with Hennepin County EMS, as he pointed to a list of disease topics on a tablet computer ­running SafetyPAD.

"Without a prompt, it can be easy to forget," he said. "It's just like a pilot going through a preflight checklist. You know what to do, but you don't want to be in the uncomfortable spot of forgetting something" if something goes wrong.

Unlike the Spokane Fire Department, Hennepin County didn't use the Ebola update — because its users had already used the flexibility of the system to adapt their questions for the disease. So far nine agencies have adopted Open's new Ebola questions, including the Chicago Fire Department and Miami-Dade Fire Rescue, which each have 2,500 providers using SafetyPAD.

In Hennepin County, Ball and the county's emergency preparedness director automatically receive an e-mail alert any time a feverish patient tells a paramedic that they've traveled to any other country in the past 30 days. Since launching the Ebola questions, the system has been flagging a few cases per week, each of which has been negative for the virus.

Right now the questions include any international travel, not just countries with outbreaks, and the alerts of potential contagion risk are sent to a small number of people. "If things go from preparedness mode, which is where we are in the Twin Cities right now, to where we have definite cases, we could change that," Ball said.