The World Health Organization (WHO) says that only “collective international public health action” will stem the spread of a future infectious disease pandemic. WHO, a United Nations agency based in Geneva, Switzerland, says the risk of a global pandemic, especially an outbreak of avian influenza, has never been higher. Its annual World Health Report warns that the threat of a “pandemic of influenza from this virus is still a matter of when, not if.”

Authorities have reported just 310 cases (including 189 deaths) of human H5N1 avian flu infections since the disease was first identified in Hong Kong a decade ago. But WHO says we should not become complacent. “Pandemic influenza would have devastating consequences,” states the report. “If a fully transmissible pandemic virus emerged, the spread of the disease could not be prevented.” It further notes that since influenza viruses are genetically unstable, it is impossible to predict which specific virus strain will be the cause of the next pandemic or where it might start.

In an effort to help countries improve their readiness, WHO introduced a new set of international health regulations this summer. Called IHR (2005), the new rules are broader and more demanding than previous regulations, with a basic aim of preventing the spread of disease across international borders. The objective is to have detection and control systems fully in place by 2012.

International action has become more necessary—and more challenging—as transportation networks become more interconnected. Dr. Otávio Oliva, an influenza pandemic expert at the Pan American Health Organization in Washington, D.C., says, “The world, as well as flat, has become very small. Transmission times for diseases have fallen. You’ve got a week, at the most, to detect and control an outbreak.”

Another factor in assessing world health risks is that infectious diseases have been emerging at a faster rate in recent decades than in years past, the report notes, although this may be because researchers have become better at detecting them. Scientists now know of nearly 40 diseases that were unheard of a generation ago.

Equally disturbing, many diseases that were once substantially contained, such as cholera, malaria, dengue fever, and yellow fever, have made a comeback. Polio, once controlled, has returned to west and central Africa. HIV-AIDS continues to infect millions, especially in Africa. And tuberculosis, once waning, now kills 1.6 million people yearly.

However, none of these diseases rival the influenza virus in its ability to rapidly infect and kill a large number of people. The death rate during the 1918 to 1919 influenza pandemic was around 2.5 percent. Experience from past pandemics indicates that around 25 percent to 30 percent of the world’s population—more than 1.5 billion to 2 billion people—could be affected in a worst-case outbreak. A human strain of avian flu with the same lethality as H5N1 could kill 100 million people.

The WHO report highlights that adequate safeguards can limit the impact of a pandemic. It says the 2003 SARS epidemic in Asia could “possibly have been a global pandemic responsible for millions of deaths. Instead, using classic surveillance and epidemiological response techniques, the epidemic was limited to 8,422 cases.”

The SARS outbreak killed 11 percent of those it infected and the cost of prevention was high. Affected countries spent about $2 million per person infected.

International cooperation will be crucial in containing future epidemics. China, which used to suppress news about disease outbreaks, has improved its monitoring and dissemination capability. But Indonesia remains a key battleground. It has suffered 106 cases of H5N1 and 85 deaths since 2003, more than any other country. Yet its officials have a poor reputation for international cooperation and effective internal controls.

One potential aid: the Internet. It now ensures that these epidemics can no longer be kept secret. The report says that in future, “non-state sources of information about outbreaks will often pre-empt official notifications. This includes situations where countries may be reluctant to reveal an event in their territories. WHO is now authorized through IHR (2005) to take into account information sources other than official notifications.”

WHO’s new rules also mark a shift from reliance on controls at airports and ports to block the import of cases toward rapid responses at the source of an outbreak. WHO says its Global Outbreak Alert and Response Network (GOARN) can deploy response teams to any part of the world within 24-hourse to support local public health agencies. 

Many governments have also stockpiled antiviral drugs to immunize some parts of their populations. WHO and some member states have created international stockpiles of oseltamivir, an antiviral drug that could stop early stage transmission, but the organization notes that this would only confer partial protection. It would take research laboratories time to isolate a new virus and develop an effective vaccine specific to the new outbreak.

Vical, a California-based vaccine company, says it has begun human trials of a new pandemic influenza vaccine, which it claims could protect against the H5N1 virus and stimulate immune responses for cross-strain protection too.

In addition to stockpiling antivirals, many governments have developed pandemic plans. However, influenza expert Oliva warns that “A good plan only works when... people are being trained.”

Furthermore, not all governments have prioritized how drugs and medical equipment would be distributed in an emergency. Lori Uscher-Pines, a researcher at Johns Hopkins University, found that of 45 government plans surveyed last year, one-third had not consistently prioritized who should get antiviral medications, vaccinations, and critical medical resources such as ventilators or face masks.

Of the 28 countries that said they had determined who would have priority rights to such resources, health workers were most often designated as the first to receive vaccines or antivirals. Many governments differed on which groups—essential service workers or high-risk groups like the elderly or the young—would be next in line to get the drugs.