“The world is now at the start of the 2009 influenza pandemic,” World Health Organization (WHO) Director-General Dr. Margaret Chan declared Thursday.

For virologists, epidemiologists and public health authorities who’ve been carefully monitoring the H1N1 flu virus since it began its global onslaught roughly two months ago (though it’s likely been around undetected for much longer), WHO’s announcement wasn’t a surprise. Many authorities had expected a pandemic to be declared much earlier.

Just last month Chan warned that “we expect [the] pattern of international spread to continue."

There are nearly 30,000 confirmed cases in 74 countries, more than 13,000 of which are in the United States spread across every state. H1N1 has killed 27 people in the US, which also isn’t a surprise. Early on, US public health authorities warned that as the virus spread there would most certainly be deaths in the United States.

“And there will be more [illnesses and deaths] – how many more we don’t know,” HSToday.us was told by a government public health official who has been intimately involved in monitoring and preparedness since H1N1 was first identified.

“On the basis of available evidence and ... expert assessments of the evidence, the scientific criteria for an influenza pandemic have been met,” Chan said at the briefing Thursday to announce that a pandemic officially was being declared.

“Spread in several countries can no longer be traced to clearly-defined chains of human-to-human transmission. Further spread is considered inevitable,” Chan said, noting that “we are in the earliest days of the pandemic. The virus is spreading under a close and careful watch.”

Chan added that “no previous pandemic has been detected so early or watched so closely, in real-time, right at the very beginning. The world can now reap the benefits of investments, over the last five years, in pandemic preparedness.

Department of Health and Human Services (HHS) Secretary Kathleen Sebelius stated that WHO’s “decision … was expected and doesn’t change what we have been doing here in the United States to prepare for and respond to this public health challenge. Once we saw how fast this virus was spreading, we activated our pandemic plans and started doing all the things we needed to do to keep the public as safe and secure as possible.”

“What this declaration does do is remind the world that flu viruses like H1N1 need to be taken seriously. Although we have not seen large numbers of severe cases in this country so far, things could possibly be very different in the fall, especially if things change in the Southern Hemisphere, and we need to start preparing now in order to be ready for a possible H1N1 immunization campaign starting in late September.”

“We responded to the H1N1 outbreak from the outset with the presumption that a pandemic was likely, so this decision comes as no surprise,” added Homeland Security Secretary Janet Napolitano. “We acted aggressively to stay ahead of the virus as it spread across the country. Now our challenge is to prepare for a possible return in the fall."

Napolitano said "the Obama Administration has been working together across the government and will continue to do so over the weeks and months ahead to keep the American people safe. We are reaching out to our partners in state and local government, in school districts and the private sector to urge them to modify and update their pandemic plans. We are working with our scientists to test and prepare a possible vaccine. And we are working with governments around the world to share what we know and learn from what is happening in their countries.”

Coupled to fears that this new influenza virus could mutate into a much more lethal strain, one perhaps resistant to antivirals –which it still could – federal, state and local authorities across the United States began mobilizing for a potentially more serious outbreak in the Fall. An outbreak more and more authorities are concerned will occur.

With so much uncertainty about H1N1, authorities have had no choice but to prepare for the worst. The ongoing spread of H1N1 continues to serve as a genuine test of the public health system's ability to respond to an emerging, large scale public health threat and a re-evaluation of overall national preparedness for a lethal pandemic.

Among the issues federal and state public health authorities are grappling with is when to begin making potential vaccines, how to best use antivirals, and whether hospitals in particular are prepared for a surge of flu victims next season. Indeed.

Connie Potter, executive director of the National Foundation for Trauma Care, which has been monitoring the flu-related surge of overcrowding in emergency rooms in some parts of the nation, said hospitals have experienced surge-related problems as expected.

“Once again, as we’ve long been warning, many hospitals are not prepared for a surge of patients” from a mass casualty crises, be it a pandemic  or a terrorist attack, Potter said.

Preparedness for mass casualty event is a problem public authorities have been warning about for years, as HSToday.us and  Homeland Security Today have been reporting.

"This virus has followed the pattern of all the historic pandemics we’ve experienced, but we also missed some precursor signals," said Dr. Carol J. Cardona, a virologist who is an expert in how viruses damage their hosts at the Department of Population Health and Reproduction, and professor in the School of Veterinary Medicine, University of California, Davis.

Speaking at the American Thoracic Society International Conference on May 20, Cardona said H1N1 "sneaked in the door while health authorities who should have known better were busy closing windows.”

Acting Chief/Science Officer of the Centers for Disease Control and Prevention’s (CDC) Emergency Operation Center, Rear Admiral Dr. Kenneth G. Castro told conference attendees that the concern that H1N1 will become a pandemic flu virus “is what we are preparing for and worrying about.”

Echoing many other experts, Castro predicted that we haven’t seen the end of H1N1. "Clearly, this virus has readily spread across the [United States] at a time we're no longer experiencing influenza. The criteria for this virus have nothing to do with the severity problem in pandemic planning. This is very likely to be circulating and you can expect to see it again when our virus season occurs."

Dr. Daniel Jernigan of CDC's Influenza Division earlier had warned that “this is an ongoing public health threat."

“What’s going to happen if H1N1 emerges next flu season is probably a lot more of what we’re already seeing ,” said Tim Stephens, a noted emergency public health preparedness advisor.

Authorities continue to be concerned about H1N1’s co-mingling with the highly lethal H5N1 avian flu virus once H1N1 begins spreading widely throughout Asia where H5N1 continues to be a problem. H5N1 is the flu virus most authorities have long feared would be the strain that would mutate into an easily human transmissible form, triggering a deadly planetary pandemic.

CDC and other authorities also are concerned that as H1N1 co-mingles with regular seasonal flu strains, especially the ones that have shown resistance to antivirals, that a much more infectious resistant H1N1 strain might emerge. The worst case scenario would be a more lethal H1N1 variant against which antivirals have no effect.

Public health authorities have prepared for the possibility that the H1N1 virus will not die out in the coming summer months as is typical for seasonal flu viruses, and that it could re-emerge in the fall in a much more dangerous form, as has happened in past pandemics.

"CDC is preparing for the possibility that [the H1N1 virus] may continue to circulate at present levels through the summer," said Jernigan.

Virologists are especially worried about what will happen as the virus moves through the southern hemisphere, which has entered its winter flu season, and co-mingles with other influenza strains.

CDC director spokesman Von Roebuck said “we’re watching very closely what’s happening with H1N1 in the southern hemisphere. We believe this will tell us a lot about what’s going on with it with regard to what we may expect next [flu] season.”