The government has stepped up preventive measures against the spread of swine flu, ordering travelers returning from Mexico to undergo medical checks at Ben Gurion International Airport. Prime Minister Binyamin Netanyahu's office said Thursday he also instructed the Health Ministry to increase stocks of antivirus medicines above the levels recommended by the World Health Organization. It gave no details, but medical experts say Israel already has enough medicine to treat nearly one-fifth of the population. Thursday's moves followed the WHO decision to ratchet up its global alert. Israel has confirmed two cases of the disease and says that neither patient is in danger.