Alert Green Isolated external or local cases of animal-to-human transmission. Threat of human-to-human infection remains low. The disease, if any, is basically limited to animals. Strategy is to step up vigilance and make preparations to meet the potential threat. Action: Place close contacts of cases under phone surveillance and observe them for flu-like symptoms. Encourage healthcare workers and high-risk groups to get vaccinated against seasonal flu. Instruct use of personal protection equipment for those looking after suspect cases. Advise public to practise good personal hygiene habits and responsible social behaviour.
	Alert Yellow Inefficient human-to-human transmissions of flu caused by a novel virus, requiring close and sustained contact to an index case. Further spread can be prevented through public health measures to isolate cases and quarantine contacts. Risk of import into Singapore elevated. Isolated imported cases may occur but there is no sustained transmission. Strategy is to prevent further import of cases, and to ring fence and isolate cases to prevent spread. The focus will be to provide treatment of all cases, and antiviral prophylaxis to contacts including exposed healthcare workers. Action: Alert Green action apart, institute home quarantine for close contacts of cases. Institute temperature screening and impose restriction on hospital and clinic visitors. Restrict inter-hospital movement, except in emergencies. Healthcare workers to take temperature twice a day. Institute temperature screening for passengers arriving from affected countries at border control checkpoints. Travellers from affected countries given Health Alert Notices (HANs) and advised to monitor their temperature daily for 1 incubation period.
	Alert Orange Virus becoming increasingly better adapted to humans but may not yet be fully transmissible , requiring close contact with an index case. Larger clusters appear in one or two places outside Singapore but a pandemic has not yet been declared. A cluster of cases may also occur in Singapore but human-to-human spread remains localized. Public health measures such as isolation and quarantine will be effective to break the chain of transmission. Strategy is to contain spread arising from any local cases and break the chain of transmission, while preserving essential services and resources. All the measures taken in Alert Yellow will continue where operationally feasible. Action: Implement “No visitor” rule at all hospitals. Restrict all inter-hospital movement of patients or healthcare workers. Set up Flu Clinics at the 18 Polyclinics for assessment and anti-viral treatment of flu-like patients. Commence antiviral prophylaxis for identified essential services. Encourage temperature taking at schools and all non-healthcare workplaces, markets, places of mass gatherings etc. Carry out temperature screening for in-bound and outbound passengers at all air, sea and land border checkpoints. Consider closing of schools and suspension of public gathering and events.
	Alert Red WHO declares that an influenza pandemic has begun. Singapore eventually also affected. Higher risk of acquiring the disease from the community once pandemic spreads to Singapore . Strategy is to mitigate the impact of the pandemic. All measures taken in Alert Orange will continue to be applied. Closing of school and suspension of selected events to prevent congregation of large groups of people.
	Alert Black High rates of severe disease and deaths. Emergency measures implemented to bring the situation under control. Healthcare and social support systems are overwhelmed by the pandemic. Economic activities are severely disrupted. Strategy is to ensure that medical & public health measures take precedence over social & economic considerations. Focus is to contain the “damage” and regain control of the situation, Drastic measures like stopping all social events may be implemented. The majority of measures are as in Alert Red plus the following action: Suspend all public gatherings, schools and Institutes of Higher Learning (IHL) closures. Issue advisory to public to stay home or even consider imposing curfew.