MEXICO CITY - Mexican officials voiced hope on Friday they were getting a handle on an outbreak of a new flu strain as doctors sought to understand how dangerous it is, how far it might spread and where it came from.

The U.S. Centers for Disease Control and Prevention said Mexico's epidemic of the new H1N1 swine flu virus may not be as severe as it looked at first, with many mild cases that were not immediately noticed.

In Mexico City, where many offices and businesses were closed for a five-day break to help slow the spread of the disease, Mayor Marcelo Ebrard said the country's emergency campaign against the virus was bringing results.

Individuals and families have been taking these measures very seriously and as a result we have had timely and early detection of cases of respiratory illnesses that could be of this type. This has led us to a situation where the numbers are getting better every day, he said.

I'm not saying we should let our guard down ... I'm telling you so you know where we stand.

Mexican Health Minister Jose Angel Cordova said the public hospitals that treat roughly half the country admitted just 46 patients with severe flu symptoms on Thursday, down from 212 patients on April 20.

The CDC said in a new report on Friday it had confirmed 84 out of up to 176 deaths in Mexico blamed on the H1N1 strain.

Worldwide, 13 countries have confirmed cases. The latest were Denmark and Hong Kong -- where a traveler from Mexico accounted for the first verified case in Asia.

The United States, the country with the largest number of confirmed cases outside Mexico, reported 141 cases across 19 states on Friday. Almost all infections outside Mexico have been mild, and only a handful of patients have required hospital treatment.

Only one person has died outside Mexico: a toddler from Mexico who traveled to the United States.

EXPLORING THE EPIDEMIC

Experts have been struggling to explain why so many deaths have occurred in Mexico and nowhere else. On Friday, the CDC suggested a simple explanation: there are many cases in Mexico, most are mild, and just the bad ones have been seen so far.

To date, case-finding in Mexico has focused on patients seeking care in hospitals, the report said. A large number of undetected cases of illness might exist in persons seeking care in primary-care settings or not seeking care at all.

Scientists hope to get a clearer picture as data comes in from special test kits that the CDC sent to Mexico to measure the extent of the illness. Even normal flu can be deadly, with seasonal influenza killing an estimated 250,000 to 500,000 people globally every year.

The World Health Organization said on Friday that no meeting of its emergency committee was scheduled, meaning there was no immediate likelihood of its level 5 alert being raised to a full 'phase 6' pandemic alert.

To declare a full pandemic, WHO would have to be convinced the new virus is spreading in a sustained way among communities in another region besides North America and officials said it was not clear this was the case.

On Friday, a WHO vaccine expert said there was no doubt that it would be possible to make a successful vaccine against the virus in a reasonably short period.

The WHO has said it would call the new virus strain Influenza A (H1N1), not swine flu, since is no evidence that pigs have the virus or can transmit it to humans. Pork producers had said consumers were shunning their product.

Most global markets have shrugged off flu fears as traders focused on hopes that a deep U.S. recession may be nearing an end.

ECONOMIC HIT

Some countries and sectors will suffer, however, not least Mexico. HSBC estimated that every week of the crisis could chop 0.3 percent off Mexico's annual economic output.

Continental Airlines Inc said it was halving its seat capacity to Mexico from Monday because of lower demand. The United States, the European Union and Canada have all advised citizens against non-essential travel to Mexico.

Both Roche AG's Tamiflu, known generically as oseltamivir, and GlaxoSmithKline's Relenza, known as zanamivir, have been shown to work against the new virus, and prescriptions for antivirals rose sharply in the United States amid media coverage of the flu scare.

The United States has begun sending 400,000 doses of treatment to Mexico. But Greece, which has not reported any cases of the virus, banned the export of Relenza and Tamiflu.

Mexican President Felipe Calderon has asked Mexicans to stay home from May 1 to 5 over the long Cinco de Mayo holiday, and urged businesses to close. The streets of the capital were much quieter than usual.

Mexico Medicine