Case Definition issues

This page collects observations, interpretations, and consequences action about the epidemiology of SARS-CoV2 in general. Please observe the structure of the page, when you add your content. Please use references where possible. Remember to find the relevant page. For example, if your observation is about transmission routes, please use that page, instead of posting your content here.

What is already known

2 March 2020

WHO Case Definition:

• Suspect case:
  • anyone with COVID symptoms + no other etiology + positive travel in a country with local transmission

OR

• • Anyone with COVID symptoms + close contact to a confirmed case

OR

• • a hospitalized SARI case + no other etiology

ECDC Case Definition:

Implementing case definition changes

Observations

• WHO (and ECDC) published their new recommendation on COVID case definition on March 2: this contained a significant shift from the previous approach
  • Countries were not informed in advance by WHO/ECDC that this was coming out. Some had just updated the national protocol and distribute it widely to hospitals and PH authorities, moments before receiving the updated approach from WHO.
  • This created much anxiety. Experts were surprised that WHO did not distinguish between countries with "local transmission". De facto, the majority of returning travelers now came from Corona-Risk areas.
  • This new approach had a significant impact on testing demand, generating discussions on how to deal with that. In addition, it impacted on case identification among the hospitalized SARI cases. Much time was spent (and lost?) on discussing priorities for testing.

Analysis and interpretation

• This led to some countries still having no updated policy two weeks after the new case definitions were published, and as a consequence, most of the medical staff was still focussing on people coming from the original high-risk areas or contact with a confirmed case only; as a consequence, new COVID19 cases remain unreported.
• Some experts strongly disagree with WHO about the need to exclude other etiology first. The recommendation is probably aimed to decrease the need for COVID-19 testing, but the fact that this leads to a significant delay in the COVID-19 diagnosis (and thus increased exposure of healthcare workers to undetected COVID-19) some public health experts find hard to digest.

Consequences for action

• Countries should be prepared to rapidly shift gear when international case guidelines change. During pandemics, it is unrealistic to expect that coordinating organizations such as WHO and ECDC can predict when they will change guidelines, so one cannot expect timetables for this.
  • Communication channels from national public health bodies to health care professionals should allow for such rapid changes, and a platform of rapid exchange of information and advice would be beneficial.
  • Health care providers on their term should be prepared to receive rapidly changing guidelines during international infectious disease crises. What is considered a constant among all large pandemics, is that gaps in knowledge are rapidly filled; therefore new insights have to be translated to an improvement of prevention and control in a timely and efficient way.
  • The best way for countries to prepare for this, is to have regular simulation exercises that take these issues into account.