Updated

Just as Category 4- and Category-5 hurricane warnings help citizens prepare for catastrophic storms, a new set of guidelines from the Centers for Disease Control and Prevention includes a five-level "pandemic severity index" based on projected fatalities to help states understand when to take drastic measures.

Click here to read the CDC's pandemic mitigation recommendations.

The CDC guidelines issued Thursday, the government's most specific flu preparedness recommendations yet, stop short of directly advising states on when to implement critical prevention measures, such as closing schools.

But the benchmarks may help state and local leaders, businesses, schools and families better prepare for superflu and lessen economic fallout.

"It became clear about a year ago that we're probably not going to be adequately prepared when the first wave of a pandemic hits," said Dr. Michael Sauri, of Occupational Health Consultants, a Maryland-based consulting firm.

"But, if we harden our business and communities to the effects of pandemic flu, then we can minimize the economic impacts and social disruption," Sauri said. "In order to do that, it's helpful to have these guidelines based on prevalence of the disease."

A pandemic flu could last months and have several waves, with a second wave starting three to 12 months after the first, according to the Maryland Department of Health and Mental Hygiene.

When a pandemic begins, a well-matched pandemic strain vaccine will likely not be available, the CDC recommendations say. Communities must prepare to cope with a first wave without vaccine and potentially without enough antiviral medication to fight massive spread.

"The community is left having to initiate, as they did in 1918, self-shielding or social-distancing strategies," Sauri said. In the past, ad-hoc community strategies to cope with rampant flu ranged from closing movie theaters to alternating patterns of work in factories.

The CDC recommendations focus on non-pharmaceutical interventions that can be used to help delay mass contagion, "buy time" for production and distribution of an effective vaccine and reduce deaths in a community during a pandemic's first wave.

They include: voluntary isolation and quarantine of infected individuals and their contacts; canceling public gatherings; instituting liberal work leave policies and "teleworking strategies", and mass dismissal of students from schools, universities, day-care centers and other child care programs.

Based on the new severity index, the Spanish Flu of 1918 , which killed over a half-million Americans and an estimated 50 million people worldwide, according to the CDC, would be considered a Category 5 flu. The 1957 and 1968 pandemic influenzas would fall under Category-2. The average seasonal flu constitutes a Category-1.

In Category-4 and -5 pandemics, at least 900,000 U.S. deaths are projected. The CDC recommends isolating and quarantining infected individuals and household members, altering workplace schedules and practices, and closing schools for up to three months.

In a Category-2 pandemic, 90,000 to 450,000 U.S. deaths are projected. Communities should consider, but not necessarily act on, halting mass gatherings such as stadium events, modifying workplace schedules and shifts and closing schools, day care centers and other child care programs for up to one month.

"I think one of the hardships of national plans and guidelines is that it doesn't take differences into account, like population density and school configuration," said Mary Kusler, assistant director of government relations for the American Association of School Administrators.

A crowded urban school district might need to handle a pandemic threat differently than a small community school district in a rural area, Kusler said.

"Guidelines on a national level, how useful they are, I don't know," said Carl Roberts, superintendent of Cecil County (Md.) Schools. "But, they do cause discussions."

For example, Roberts said, the schools have been good at educating students and the community about hand-washing to prevent the spread of viruses, however, more drastic measures may be a matter of money.

"What we don't have a handle on is closing school for extended periods of time," Roberts said. "My community is not at this point ready to receive instruction, nor is my community ready to deliver school instruction remotely on a massive scale."

Preparing a school district to operate remotely during a pandemic, he said, will require fiscal resources, and wealthier communities will more quickly be able to prepare.

The recommendations are considered useful benchmarks by some local health departments.

"There are national plans and there are state plans, but local health departments have to look at these plans to see how they can best apply to individuals in local communities," said Elin Jones, spokeswoman for the Anne Arundel County (Md.) Health Department.

Jones' department will compare the guidelines to a plan it began developing in 2005, she said. "Our (flu preparedness) plan is a work in progress, so we're always looking at ways to improve."

Capital News Service contributed to this report.