Mexico readied a "temporarily closed" sign - taking the drastic step of ordering a suspension of nonessential federal government and private business activity as it tried to squelch a swine flu epidemic. The World Health Organization ratcheted up an alert and warned that "all of humanity" is threatened. The dire warning showed that health officials are very worried about the potential for massive numbers of deaths worldwide from the mutated virus, even though the epidemic so far has claimed only a confirmed eight lives in Mexico and one in the United States. Roughly 170 deaths are suspected of having been caused by the virus in Mexico. Switzerland on Thursday became the latest country to report a swine flu infection - a 19-year-old student who health officials said was mistakenly released from a hospital and then hastily readmitted. European Union health ministers held emergency talks in Luxembourg to coordinate national efforts to prevent the spread of swine flu in Europe. The Phase 5 alert, indicating a pandemic could be imminent, prompted Mexico to announce the partial May 1-5 shutdown, Mexican Health Secretary Jose Cordova said late Wednesday. In Washington, President Barack Obama promised "great vigilance" in confronting the outbreak that has sickened at least 93 people in 11 states and forced schools to close, affecting 130,000 students in Texas alone.