The United States and other northern countries are bracing for a second wave of swine flu infections that could sicken millions of people and contribute to the hospitalization and deaths of thousands, including many children and young adults.
While flu viruses are notoriously capricious, making any firm predictions impossible, a second wave could hit the Northern Hemisphere within weeks and lead to major disruptions in schools, workplaces and hospitals, according to U.S. and international health officials.
"The virus is still around and ready to explode," said Dr. William Schaffner, a Vanderbilt University School of Medicine influenza expert who advises federal health officials. "We're potentially looking at a very big mess."
Since emerging last spring in Mexico, the virus, known as H1N1, has spread to at least 168 countries, causing more than 162,000 confirmed cases and playing a role in at least 1,154 deaths, including 436 in the United States.
President Barack Obama arrived in Mexico yesterday for a two-day summit that will include discussions on swine flu, along with Mexico's drug wars, border security, immigration reform and economic recovery.
"Everyone recognizes that H1N1 is going to be a challenge for all of us, and there are people who are going to be getting sick in the fall and die," said John Brennan, the U.S. deputy national security adviser for counterterrorism and homeland security. "The strategy and the effort on the part of the governments is to make sure we ... collaborate to minimize the impact."
As the first flu pandemic in 41 years spread through the Southern Hemisphere's winter over the last few months, scientists have been closely monitoring the virus for clues to how much of a threat it might pose this fall. So far, no signs have emerged that the microbe has mutated into a more dangerous form. Most people who get infected seem to experience fairly mild illness.
Still, the virus has caused major outbreaks involving a disproportionate number of younger people in Australia, New Zealand, Argentina and other countries, prompting schools to close, causing theaters to shut down, and straining some emergency rooms and intensive care units, sometimes forcing doctors to postpone other care, such as elective surgeries.
Swine flu has also begun to spread in South Africa, where at least two deaths have been reported and the national laboratory was overwhelmed last week with samples that needed testing. In India, a 14-year-old girl became the first person to die from the disease in that densely populated nation.
In Britain, meanwhile, where anxiety was running high because of high-profile cases, including Harry Potter film series actor Rupert Grint, health officials were trying to determine the cause of a sharp increase in reported cases in recent weeks.
"This is something that we could see here soon," said Arnold Monto, a University of Michigan infectious disease expert who advises the World Health Organization, the U.S. Centers for Disease Control and Prevention and other federal health agencies. He noted that some emergency rooms were overwhelmed by last spring's outbreak in New York City. "We have to be worried about our ability to handle a surge of severe cases."
Concern about a second wave has prompted a flurry of activity by federal, state and local officials, including intensifying flu virus monitoring and making plans to distribute vaccine and antiviral drugs and other treatments if necessary.
"There's a lot of moving parts to this," said Joseph Bresee, who heads the CDC's influenza epidemiology and prevention branch. "Hopefully we won't have a panic, but instead we'll have the appropriate level of concern and response."
The Obama administration has been updating recommendations for when to close schools, what parents should do if their children get sick, how doctors should care for patients and how businesses should respond to large-scale absences. Officials are hoping to navigate a fine line, urging precautions to minimize spread, serious illness and deaths while avoiding undue alarm and misinformation.
"The last time we had anything similar to this was prior to the Internet," said one senior official who asking not to be identified last week during one of a series of background briefings for reporters.
The virus could cause nothing more than a typical flu season. But many experts suspect the second wave could be more severe than an average flu season, which hospitalizes an estimated 200,000 Americans and contributes to 36,000 deaths. Because the virus is new, most people have no immunity against it.
"This epidemic will transmit faster than usual, because the population is more susceptible," said Marc Lipsitch, a professor of epidemiology at the Harvard School of Public Health who has been helping the CDC project the severity of the upcoming wave. "It's fair to say there will be tens of millions of illnesses and hundreds of thousands of hospitalizations, and tens of thousands of deaths. What we don't know is how many tens of thousands."
Perhaps more importantly, in every country the virus has spread, it has continued to affect children and young adults much more commonly than typical flu viruses.
Most of those who have developed serious illness and died have had other health problems. But those include many common conditions, such as diabetes, asthma and obesity. Pregnant women appear to be especially at risk. And the virus can cause severe illness and death in otherwise healthy people in perhaps a third of cases.
The virus continued to simmer in the United States over the summer, causing more than 80 outbreaks in camps in more than 40 states. Officials estimate that more than 1 million Americans have now been infected. The number of cases could increase rapidly as soon as schools begin to reopen in the next few weeks and could accelerate further as cooler, drier temperatures return, possibly peaking in October.
Although strains of the virus have emerged that are resistant to Tamiflu, one of two antiviral drugs effective in treating it, scientists say both drugs generally appear to continue to be effective. The U.S. government shipped 11 million doses of the drugs to states to add to the 23 million they already had on hand and bought another 13 million doses to replenish its supplies.
hat-tip Avian Flu Diary
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