Mexico is preparing for a second wave of swine flu, looking at what worked and what didn't last spring when it banned everything from dining out to attending school in an effort to control the virus.
As the Northern Hemisphere flu season begins, the rest of the world is also studying Mexico's experience, looking for measures to replicate and costly mistakes to avoid.
So what worked? Public awareness; rapid diagnosis, treatment and quarantine; and a near-compulsive outbreak of hand-washing.
What didn't? Travel bans, school closures, overuse of antibiotics and those flimsy paper face masks that tangled hair, slid down necks and hid the beautiful smiles of this gargantuan city.
When swine flu first flared up in Mexico in April, the government erred on the side of caution, closing schools and museums, banning public gatherings, playing soccer games to empty stadiums and telling people not to shake hands or kiss one another on the cheek. This bustling city of 18 million became eerily hollow.
Mexican health officials say they made the right call.
"Since we were the first country affected by the flu, we didn't know the possible magnitude and severity, so we took measures that we now know can be (focused)," said Dr. Pablo Kuri, the health secretary's special influenza adviser.
In hindsight, Mexico's most effective action — one now emulated around the world — was immediately telling its own citizens when the new virus was detected.
Not every country has been so candid when facing an epidemic: China was heavily criticized for its slow response to SARS in 2003, while Argentina refused to declare a national public health emergency when swine flu flared there in July.
But Mexico's openness didn't come cheap: Economists say the outbreak cost the country billions of dollars, mostly in losses from tourism.
"Mexico shared information early and frequently," said Dr. Jon Andrus at the Pan American Health Organization's headquarters in Washington. "Mexico did this at great cost to its economy, but it was the right thing to do."
At the height of the epidemic in March, you could hardly make it a block in Mexico City without a masked public health worker, maitre d', bus driver or store owner squeezing a dollop of antiseptic gel onto your hands.
Health experts say hand-washing offered the best defense — while the masks probably did little to stop the virus from spreading. Masks are now advised only for health care workers and people who are already infected.
Fear also left behind a cleaner city: Crews now regularly scrub subways and buses, park benches and offices — something almost unheard of before the epidemic.
"Clearly, millions of Mexicanos wore masks this spring everywhere they went, but H1N1 continued to spread," said Laurie Garrett, a senior fellow at the New York-based Council on Foreign Relations. "It now seems clear that the best personal protections are regular hand-washing, avoiding crowded places, and — when it is available — vaccination."
Many Mexicans wait until they suffer full-blown symptoms before going to a doctor, if at all. Often, people self-diagnose and go to a pharmacy to treat themselves since few drugs require a prescription. Since April, however, certain anti-flu drugs are distributed only at hospitals.
Millions of uniformed Mexican children were greeted with a dash of anti-bacterial gel as they returned to school last Monday. Classes were postponed until mid-September in southern Chiapas state because of an uptick in swine flu cases in the past month. Chiapas has had 3,400 swine flu cases to date, the most in the country.
Schools nationwide are checking for possible signs of swine flu among children and teachers and are sending home anyone who seems sick. They also have added new curriculum guidelines to ensure children learn about personal hygiene and basic sanitation.
But this time, schools will be closed only if so many sick children or teachers get sick that education is compromised. Plans are already under way to continue lessons at home.
"We aren't going to panic, but we are being more careful here this year," said Cecilia McGregor, spokeswoman for Colegio Ciudad de Mexico, an 1,100-student private school in Mexico City.
Janitors are required to wash doorknobs every two hours, she said, and an on-campus doctor was performing checks.
Despite all the precautions, Mexico's health advisers say the most important lesson they have learned about swine flu is that in most cases, it's fairly mild.
Swine flu caused 164 deaths in three months in Mexico, where tobacco-related illnesses kill that number every day.
"So now we can put into context what actually happened," Kuri said.