point out that strategies involving a case isolation policy assume too easily that facilities to effectively isolate individuals will be available, especially when urban transmission occurs on a significant scale. If antivirals are available and useful, they may be considered in lieu of isolation (i.e., **_QA_** vs. **_QI_** ). Where antiviral stockpiles are limited, the use of large‐scale case isolation may be needed – a contingency to be planned and prepared for.

_Discussion_ : The results above indicate NPIs have a role in _mitigation_ at moderate _R0_ and _θ_ , even without TAP or vaccination in tandem. The timing requirements are not more onerous than for drug‐based strategies, but the duration NPIs have to continue to minimize the GAR – based on historical experience – may have significant societal costs. The dichotomy in NPI effectiveness seen in the modeling studies across SE Asia and the US may be due to model‐related factors. The early use of NPI intervention, limited seeding, and the lack of reintroductions in the SE Asian models may explain the observed effectiveness of NPI in containment. In contrast, given some delay in intervention start, multiple infection seeds, reintroduction risk, and widespread transmission as in the US models, a persistent decline in susceptibility and infectiousness through vaccination and/or TAP is preferred (as **_11_** in Table 9). However, pharmaceutical policies are resource and capacity intensive, and may be overkill in conditions of moderate _R0_ if a strategy of cooperative international air travel restriction mixed with border control/airport quarantine is probable. In this case, for countries at secondary risk, the policy objective resembles early containment. This implies that the choice of stringent, layered NPIs at airports and _reactive_ NPIs in communities (as **_15_** in Table 8) could minimize the attack rate. This strategy has _a priori_ lower social cost if a smaller epidemic size is assumed since widespread school and workplace closure are avoided and unfeasible contact tracing during sustained urban transmission is not required. However, in situations of higher infectivity ( _R0_ ), the primary benefit of NPIs will be to delay peak transmission such that a well‐matched vaccination policy becomes viable. However, vaccination contains the assumption of adequate antigen stocks in resource‐poor settings.

# 3. **International air travel restrictions and advisories**

The reduction in the volume of and entry‐points for incoming infectives would eliminate multiple outbreak seeding; increasing the probability of waging containment battles at airports and high risk communities rather than a large‐scale mitigation war. This could be achieved with entry and travel controls, which could also delay an epidemic peak in a country. Depending on the delay, this would enhance the viability and timeliness of other control policies from NPI to vaccination. For pandemic influenza – given higher _θ_ than SARS – symptom‐based entry screening is not expected to be an effective preventive measure<sup>18</sup> . Instead, the cancellation of flights to and from certain (or all) cities worldwide could be considered by each airport. Retrospective modeling of the 1968‐69 pandemic<sup>31</sup> suggested a role of the international air network in the spread of influenza. Recent work by Brownstein _et al._ (2006)<sup>61</sup> analyzed the ‘natural experiment’ of the post 9‐11 shutdown in US air traffic, and found it connected with a delay in the seasonal influenza peak in 2002.

However, control in an actual pandemic situation with higher transmissibility and susceptibility compared to interpandemic influenza needs to be evaluated. The success of international air travel restrictions (IATR) for pandemic control depends on a proactive WHO role, the nature of the initial outbreaks, the identification of highly connected cities that may exchange infectives (which may be isolated from each other), further analysis of the SARS experience, and some voluntary self‐restriction by travelers who expect to have been exposed to infection. There is considerable uncertainty if IATR will be effective. Modeling studies have attempted to bring greater predictability to the issue.

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