Related by context. Frequent words. (Click for all words.) 45 vigilance 43 heightened 43 heightened alert 38 alert 37 remain vigilant 34 Heightened 34 preparedness 34 terrorist attacks 34 bioterrorism 33 precautions 33 subways 33 vigilant 32 precautionary measures 32 Homeland Security Secretary 32 urgency 31 heightened tensions 31 alertness 31 wariness 31 heightened tension 31 reprisal attacks 30 panic 30 attacks 30 pandemic influenza 30 scrutiny 30 compromised immune 30 intense scrutiny 30 foiled plot 29 radiological 29 extreme caution 29 influenza pandemic 29 counter terrorism 29 emergency preparedness 29 Chertoff 29 calmness 29 counterterrorism 29 complacency 28 threat 28 countering terrorism 28 intensification 28 spokesman Russ Knocke 28 pandemic 28 threats 28 quarantine 27 anxiety 27 chemical biological radiological 27 terror 27 preventive measures 27 parcel bombs 27 bomb sniffing dogs 27 unease 27 precaution 27 strictly enforce 27 communicable diseases 27 combating terrorism 27 skepticism 27 bird flu pandemic 27 air marshals 27 intensity 27 retaliatory attacks 27 nervousness 27 concerted 27 unprecedented 26 pat downs 26 threat posed 26 security 26 caution 26 terrorism 26 precautionary 26 radiation detectors 26 nonessential travel 26 vulnerability 26 renewed 26 apprehension 26 outbreaks 26 redouble 26 travel advisories 26 intensified 26 paranoia 26 avian influenza 26 lockdowns 25 tighter controls 25 beefed 25 potentially hazardous 25 assertiveness 25 openness 25 homegrown terrorists 25 disenchantment 25 patrols 25 sophistication 25 priority 25 concern 25 pandemic preparedness 25 act decisively 25 surveillance 25 flu pandemic 25 disquiet 25 confidence 25 revulsion 25 ramped 25 pandemic flu 25 clampdown