Table 3.

Bias assessment tool

Criteria	Points
Index case classification
Laboratory confirmation	1
Unspecific clinical presentation or data not provided	0
Secondary case ascertainment
Laboratory testing of possible cases on flight	2
Syndromic (i.e. MERS-CoV-like illness) or no comprehensive confirmation of all possible cases	1
Not provided	0
Public health interventions
Contact tracing of flight passengers	2
Other	1
No intervention conducted or not mentioned	0
Timeliness of contact tracing of flight
Within 1 week	2
Within 2 weeks	1
3 weeks or more	0
Proportion of aircraft contacts followed up
More than 80% followed up	2
Between 50% and 80% were followed up	1
Less than 50% were followed up or retrospective identification	0
Limitations
Alternative exposure before flight possible/alternative exposure not addressed	−1
Resulting evidence levels: 0–4 low, 5–7 medium, 8–9 high.