this past friday, dr. michael ryan, executive director of the world health organization’s health emergencies programme, noted that in the current context, covid-19 “elimination” in most places is unlikely. elimination refers to zero cases of covid-19 in a particular geographic area, such as a country, while eradication refers to bringing the global burden of cases to zero, which would be extremely difficult to achieve. exceptions to this mainly included such geographically isolated countries as new zealand that have been able to drastically reduce covid cases, which is not possible in other areas of the world; however, even in these situations, as borders reopen, there will likely be a resurgence.
what does it take to get an infectious disease eliminated? there are four major principles to eliminate an infection within the human population:
• a biologic intervention that prevents transmission of the disease in nearly all individuals, for example, a vaccine.
• a diagnostic test that picks up the vast majority of, if not all, cases.
• a surveillance system to detect cases as the disease nears elimination and afterwards to ensure there is no rebound.
• no other place for this infection to hide, and then reinfect humans, such as an animal “reservoir” — a disease that exists naturally among animals and can be transmitted to humans cannot be eliminated by defeating it in human hosts alone.