WALNUT CREEK, Calif. — Ironically, the late-spring outbreak of the swine flu might offer the best-case scenario for controlling the spread of swine flu, many health experts say.
That’s because it has provided a prelude of what’s to come this fall.
These kinds of “herald waves” preceded past pandemics in 1918 and 1957.
This time, flu monitoring systems, combined with the unusual timing of the outbreak, allowed public health experts to detect the strain before its expected retreat this summer.
“It’s one possible scenario, and it’s the best possible scenario,” said Dr. Paul Glezen, a flu specialist from Baylor College of Medicine in Houston who coined the term “herald wave” in a 1982 journal article.
Glezen used it to describe an unusual pattern he found in flu outbreaks, in which a new flu strain emerged toward the end of the season and then returned to cause the next year’s outbreak.
That happened in the 1918 pandemic, which killed about 50 million people worldwide. Glezen said researchers realized in retrospect that there was an earlier outbreak in 1917 that heralded the pandemic. In that outbreak, soldiers at a French military camp died from the flu.
The 1957 Asian flu, which killed 2 million people worldwide, also began with a herald wave in the spring in China.
“It spread throughout the summer months around the world at low levels, and then expanded in the late fall to a large number of cases,” said Dr. Robert Belshe, who runs a vaccine development center at St. Louis University’s School of Medicine in Missouri.
“Yes, I agree we might be seeing the herald wave for the fall epidemic,” Belshe said of the swine-flu outbreak.
Many public health experts expect the swine-flu virus to retreat during the summer, when temperatures and humidity work against the microbe because it spreads best under conditions of low humidity.
In a Friday press briefing, Centers for Disease Control and Prevention officials said the CDC and other global health organizations are working with vaccine manufacturers on the early stages of vaccine development and to swiftly ramp up production for a swine-flu vaccine if deemed necessary.
Latest developments
• Deaths: 19 confirmed in Mexico and one confirmed in U.S., a 21-month-old boy from Mexico who died in Texas.
• Confirmed sickened worldwide: 809; confirmed sickened in U.S.: 197.
• Mexico’s health secretary says confirmed swine-flu cases have increased to 473, including 19 people who died. Jose Angel Cordova is urging citizens not to let their guard down, even though cases outside Mexico suggest the flu strain is weaker than feared.
• U.S. President Barack Obama urged caution Saturday in his weekly radio and Internet address. “This is a new strain of the flu virus, and because we haven’t developed an immunity to it, it has more potential to cause us harm,” Obama said. Later, he spoke with Mexican President Felipe Calderon for about 20 minutes to share information.
• The U.S. Centers for Disease Control and Prevention says about a third of the confirmed U.S. cases are people who had been to Mexico.
• A World Health Organization official said Saturday that he thinks the agency’s infectious-disease alert level ultimately will be raised to its highest point. “We have to expect that Phase 6 will be reached,” said Michael Ryan, the agency’s director of global alert and response.
• Canadian officials say pigs in Alberta have been infected with the new swine-flu virus and are under quarantine.
• U.S. Sen. Mark Udall, D-Colo., said the spread of swine flu stresses the importance of investing in research on infectious diseases. He toured an infectious-disease center at Colorado State University on Saturday.
The Associated Press
