When Patrick Henshaw's son became sick last Friday, little did he know that the 18-year-old had acquired a potentially deadly disease that made its way across the U.S.-Mexico border -- the swine flu.
"It started out where he was sick earlier in the week. Then there was a message ... from the superintendent of our school that two children had tested positive for the swine flu virus, so ... we had him tested for that. And they said, 'Oh my gosh, he tested positive,'" Henshaw told ABC News.
Hayden Henshaw is one of three students at Byron Steele High School in Cibolo, Texas, who acquired the virus. Two were diagnosed earlier this month. Henshaw believes the virus came from Mexico to San Antonio, where the annual Fiesta San Antonio draws hundreds of people from around Texas. Henshaw and his 11-year-old daughter, Hannah, were also diagnosed positive for the swine flu strain.
Cases have been reported from West Coast to the East Coast of the United States, and in Mexico, as many as 68 people have died from it. And now, New Zealand and France have reported suspected cases, too.
The World Health Organization (WHO) warned Saturday that the swine flu outbreak could potentially develop into a pandemic. In an emergency meeting Saturday, WHO Director-General Margaret Chan said the North American outbreak of a never-before-seen virus was a very serious situation.
The Henshaws know how dire the situation is. They have not been able to leave their house since the high schooler became ill earlier last week.
"They wanted us to stay in the house, and they won't let anyone stay in the house," Henshaw said. "Hayden's in the house. They told him to stay in his room for five days. We were told not to go in and out and interact with other people [for an indefinite amount of time]."
His daughter also stopped going to school on Friday, when the state's health department confirmed that Hayden tested positive for the swine flu. But Henshaw -- whose cousin delivers food for the family at their doorstep -- still feels thankful that his son's condition is improving.
"It's not like 'ET' where they have a tent wrapped around our house or anything," he told ABC News. "I hate to know that someone got sick because we leave the house. So we are going to stick by the rules. ... We will stay as long as it takes; because of the seriousness of what's happened south of us, I think it's important that word gets out. ... I'd like for us to be a positive spin on this."
The Henshaws say they are not scared because the health agencies are working quickly to find a resolution for the issue.
"I'd feel a lot worse if it weren't so many people already involved and trying to take care of this. It's calming to know," he said. "Last week there were a lot of children sick at school. ... Who knows how many more are sick with this?"
WHO officials say they are investigating the outbreak of the never-seen-before virus, which is a combination of the swine, bird and human flu strains. Its symptoms are like any other flu -- coughing, sneezing, runny nose, joint aches, headaches, high fever -- which makes it even more difficult to diagnose.
WHO spokesman Gregory Hartl said many questions remain but concerns are high.
"We're not sure exactly of the transmission routes, where the initial infection came from, how efficient it is in transmitting," Hartl said.
None of the people who have so far been reported to have caught the swine flu had any contacts with pigs, which is how experts say the flu is passed, creating an alarm that the virus can easily spread from person to person.
Dr. Martin Blaser, a professor and chairman of the Department of Medicine at New York University Medical Center, said the situation is uncommon.
"Swine flu cases occur. They're usually in people who work with swine. This is spilled out into the general community," he said.
From across the United States, health officials are issuing strong warnings. Doctors and hospitals in California are being told by the state to report any cases with flulike symptoms. California Gov. Arnold Schwarzennegger is activating the joint emergency operations center to help deal with the threat.
Tests on 75 children who fell ill with flulike symptoms at the same time in a New York school showed that eight or nine strains have mild symptoms of "probable case of human swine influenza," New York Health Commissioner Thomas Frieden said Saturday.
Wilma J. Wooten, president of the San Diego Society of the National Medical Association, said public health experts are concerned about the outbreak.
"More than likely we will have additional cases of the swine influenza virus here in our country," she said. "We want people to stay at home if you are sick. Do not go to work. Do no go to school. Do not travel -- airplane, bus -- no form of travel."
The Centers for Disease Control's (CDC) acting director, Richard Besser, also echoed remarks made by WHO yesterday, that the outbreak could be the next flu pandemic.
"This is something we are worried about and we are treating very seriously," he said.
It has made more than a thousand people sick in Mexico, mostly between the ages of 25 and 45. In the country's capital, the mayor on Saturday cancelled all public events for the next 10 days. Mexico City was quiet as schools, libraries, museums and public buildings also closed down. People were wearing masks to prevent themselves from catching the unique virus.
The White House said President Obama is being kept up to date on the situation. The Homeland Security Council, under the leadership of terrorism czar John Brennan, is heading up the administration's handling of this situation -- and working with the CDC, the State Department and the Mexican government.