In 1918, the Spanish flu infected about one-third of the world's population and killed some 50 million people. Some died within hours of the first symptoms.

Nearly 100 years later, the threat of influenza still looms. "A highly virulent strain similar to 1918 could have a similar impact today," says John Brownstein, a public health surveillance expert and professor at Harvard University.

Scientists have worked for decades to speed threat detection, improve preventative vaccines, and reduce response time during an outbreak, but the question persists: A century after the Spanish flu, how far have we come in our ability to prevent and fight infectious and newly-emerging diseases?

UNIVERSAL CHALLENGE

Though medical knowledge, technology and communication has come a long way in the past 100 years, Brownstein says that, “vaccines are still our main weapon.”

Recently, the U.S. government and the private sector have focused specifically on expanding the nation’s vaccine supply and improving effectiveness. Advances include vaccines targeted for people 65 and older who are among those at greatest risk — and a ‘quadrivalent’ vaccine that protects against four flu strains. Some researchers are trying to create the holy grail: a universal vaccine. It would offer broad immunity against all influenza infections rather than targeting the constantly-changing surface antigens of a virus, as current vaccines do. That appears to be years away.

In the meantime, Brownstein says, “We face this onslaught of misinformation” about vaccines and their potential side effects. Those misconceptions are mostly associated with the measles, mumps and rubella vaccine, but hesitancy extends to other vaccines as well. To combat this, Brownstein says the public health community needs “to report fact-based discussions in public health.”

DETECTION AHEAD OF RUNAWAY INFECTION

Beyond preventing outbreaks in the first place, rapidly detecting them is the next best thing, says Paul Biddinger, vice chair for emergency preparedness at Massachusetts General Hospital: “It gives you an opportunity to intervene.” As global travel and trade continue to increase, so too will the need for accurate and rapid threat detection.

As it stands, the first reliable testing in the U.S. for an emerging flu strain happens at the Centers for Disease Control and Prevention (CDC) in Atlanta. Only once an outbreak is well underway are these tests distributed to state labs and then hospitals.

For example, during the 2009 swine flu epidemic, it took three weeks for the diagnostic to be developed, manufactured and distributed. Biddinger notes, “By the time many are diagnosed, they’ve been in the community — or the hospital — potentially infecting others.”

While current ‘rapid influenza diagnostic tests’ can be administered anywhere and give results in 15 minutes, false negatives are common — and they don’t distinguish between seasonal flu and the more virulent influenza A viruses. More sensitive tests are needed.

SOUPED-UP SURVEILLANCE

When a threat is detected, it should be met with a robust public health response. If not, a few infections could blossom into an epidemic. To fashion that response, says Stephen Redd, director of the CDC Office of Public Health Preparedness and Response, scientists first need to understand the enemy: how a virus is transmitted. They can then determine the level of quarantine necessary for patients in hospitals, whether to move stockpiled anti-viral drugs to state health departments — and whether to close schools to limit transmission.

Those who have developed solid emergency plans will fare best, says Daniel Kollek, director of the Centre for Excellence in Emergency Preparedness at McMaster University. Those communities will have identified clinics, schools, universities and other public spaces to care for patients and set up home-care strategies. A plan will be in place for highly contagious pathogens, like Ebola, which require medical teams to wear protective clothing. That, Kollek notes, is problematic, since protective gear is not widely available and requires intensive training to use without self-contaminating.

But planning is not enough. “You need full-scale drills,” Biddinger says. “Places that have not practiced will not be ready,” because “response to disasters has so much commonality that you don’t practice the disaster, you practice the response.”

There have been some big leaps forward in datasharing across the United States and internationally that have saved lives. Within weeks of the emergence of SARS in Hong Kong, for example, researchers determined that only those with active symptoms were contagious. “That allowed global public health agencies to shut down a rapidly-spreading epidemic,” says Biddinger, which he calls “unprecedented.”

However, influenza is harder to control than emerging diseases like Ebola since it can be transmitted before a patient even shows symptoms. “If you want to look into your crystal ball,” Biddinger says, “flu remains our number one global infectious disease threat.”