EVERY year approximately 10,000 Mexicans die from the effects of seasonal flu. Usually they are the elderly and the very young, people whose immune systems are not robust enough to fight off the virus. But this year has been different. The Mexican disease surveillance system, a network of more than 11,000 hospitals, clinics and doctors’ offices, picked up a minor but troubling trend in April. Across this nation of 110 million people, a handful of young adults had apparently died from influenza. An immediate investigation led, within a few hectic weeks, to the isolation and full genetic sequencing of the microbe causing the illness. The experts’ worst fear was confirmed: it was a new kind of influenza virus.
Some have complained that the Mexican government did not act fast enough to identify this new bug and sound the alarm. But such criticism fails to take into account the real-life complexity of recognizing and responding to an unexpected public health emergency.
As a former minister of health for Mexico, I met with Mexican officials this week to consult with them on their response to the influenza, and I was impressed by how medical scientists in the country quickly perceived the unusual trend of illness against a background of standard flu and then analyzed the virus and alerted global health authorities. Their fast action gave other countries the warning they needed to screen for the new virus, which is why cases of swine flu have already been discovered in a dozen other countries — cases that might otherwise have long gone unnoticed.
The number of confirmed deaths in Mexico from this new virus is still uncertain and may be only several score. Further epidemiologic detective work will tell us whether the virus had been circulating throughout the seasonal flu period in Mexico, beginning as early as last fall, making thousands only mildly ill, and alerting us to its presence only with the unexpected deaths of young adults.
From the moment this so-called swine flu was identified, the Mexican government worked vigorously to contain the contagion — closing all schools across the country, limiting public gatherings and instructing people to wear masks and refrain from greetings involving physical contact. President Felipe Calderón himself led the response, underlining the seriousness of the situation, and that may explain why so many Mexicans have complied. Already, the number of deaths seems to be stabilizing, perhaps indicating that the first wave of this influenza has peaked.
It’s still not known why this flu seems to have been deadly only in Mexico. It stands to reason that for the entire winter flu season, Mexican doctors, not knowing that a new virus was afoot, saw any instances of it as ordinary seasonal flu, and thus did not give patients the antiviral drugs that could have saved their lives. These medicines are effective only if given within 48 hours of the onset of symptoms.
Like many other countries, Mexico had been preparing for an outbreak like this. The deadly 2003 epidemic of SARS and the 2005 outbreak of avian flu taught the world to expect that another microbial agent from animals would one day again infect humans. Over the past six years, Mexico bolstered its disease surveillance systems, built up public health laboratories, cooperated in developing international networks for information sharing and devised response plans. At the same time, the international community was stockpiling antiviral drugs, and scientists were improving their ability to understand new viruses. Most important, the World Health Organization’s International Health Regulations were written to hold countries accountable for monitoring disease outbreaks, publicly reporting all information and cooperating with other countries.
Since the 1980s, Mexico has been strengthening its epidemiologic intelligence service, in cooperation with the United States Centers for Disease Control and Prevention. Hundreds of Mexican doctors and other health professionals have received advanced training in epidemiology. In recent years, Mexico has worked with Canada, Japan, the United States and several European countries to establish the Global Health Security Action Group, a tight public health communications network. Unknown to most people, an army of epidemiologists operates around the clock to defend against microbial threats. Whether this system might have worked even more quickly in the present outbreak can be examined later; for now we must move forward with the knowledge we have in hand.
We don’t have a lot of time. Viruses are sensitive to seasonal temperature change, and this one, like the 1918 influenza, may reappear more robustly in the fall. It is critical to ascertain, from blood tests, the true number of swine flu cases worldwide, both mild and severe. Also, a sound epidemic curve needs to be established, which would reveal how the virus blossomed outward from initial cases and make it possible to quantify its transmissibility. And while we wait as much as six months for a vaccine to be readied, we need to pinpoint the best treatment strategies.
Sadly, it takes a cluster of casualties to alert the world that humans are once more under attack and that we need to marshal our scientific forces. This is, as it must be, a global challenge. With international cooperation, we have reason to hope that casualties will be fewer in this outbreak than they were in the last one, and fewer still when the inevitable next virus arises.
Julio Frenk, Mexico’s minister of health from 2000 to 2006, is the dean of the Harvard School of Public Health.