Nearly 6 million Americans could have caught swine flu this spring, CDC says

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Between 1.8 million and 5.7 million Americans caught pandemic H1N1 influenza this spring, as many as 21,000 were hospitalized and perhaps 800 died, according to new estimates by researchers at the Centers for Disease Control and Prevention. The estimates are necessary because many cases are not reported to public health authorities and the CDC stopped requiring laboratory confirmation of new cases because the labs were becoming overwhelmed.

Epidemiologists from the CDC and the Harvard School of Public Health made the new estimates, which cover the period from the beginning of the outbreak in April through the end of July, in the online journal Emerging Infectious Diseases. There were 43,677 laboratory-confirmed cases of swine flu during the period, 5,009 hospitalizations and 302 deaths, but researchers think those are only the tip of the iceberg. Many infections were too mild for patients to seek medical care, many physicians who were visited did not order tests and many positive test results were not reported to health authorities, so the researchers had to use well-known models of disease spread to extrapolate from the cases that were reported. Similar techniques are used each year to estimate the prevalence of seasonal flu.

The team estimated that about 79 infections occurred for every one detected, giving a mean number of victims of about 3 million. They also estimate that about 2.7 hospitalizations occurred for every one reported, giving a median estimate of 14,000. They did not directly estimate the number of deaths, but other data show that about 6% of those hospitalized died, leading to a figure of 800 deaths. When figures for this fall are included, ‘many millions’ of people have now been infected, CDC officials said.

An estimated 24.8 million doses of swine flu vaccine are now available, an increase of 1.6 million doses since yesterday, Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases, said this morning in a news conference. ‘We aren’t where we want to be, but we are seeing forward progress,’ she said. ‘Many doctor’s offices are now beginning to get doses.’

In other swine flu news:

- President Barack Obama’s daughters, Malia and Sasha, were given the vaccine last week, it was announced Tuesday, and, since then, many blogs and websites have been critical, charging the girls with jumping to the head of the line. Interestingly some of these same sites have been critical about the safety of the vaccine and have argued that if health authorities are so confident about its safety, they should have themselves and their families immunized. Apparently, you can’t please everybody.

For the record, the Obama children were not immunized until the vaccine was available for other children in the District of Columbia as well and, because of their ages, they are in one of the priority groups for vaccination. And having them vaccinated, most experts agreed, set a good example for parents everywhere.

- Antiviral drugs like Tamiflu, Relenza and now peramivir have been the mainstay of treating the very sick who have contracted swine flu, but a common, inexpensive and safe family of drugs may also be useful: cholesterol-lowering statins. In addition to their ability to lower cholesterol, the statins also reduce inflammation, which plays a role in development of the pneumonia that kills many hospitalized patients.

Dr. Ann Thomas of the Oregon Public Health Division reported at a Philadelphia meeting of the Infectious Diseases Society of America on a study of 2,800 people hospitalized with laboratory-confirmed seasonal flu in 10 states in 2007-2008; 801 of them were receiving statins, mostly people who were already on the drugs before they entered the hospital. Thomas and her colleagues found that 3% of those not taking statins died, while only about 1.5% of those receiving the drugs did. Several researchers called for testing to see if the drugs could help patients hospitalized with seasonal flu.

- Various health authorities have been emphasizing since the beginning of the current pandemic in the spring that the swine flu virus cannot be caught by eating pork. Apparently, Chinese authorities have finally gotten the message. Chinese officials said today that they will lift the ban on pork imported from America imposed last April. In 2008, the U.S. shipped nearly 400,000 metric tons of pork worth nearly $690 million to China, but so far this year, shipments have been about half the amount shipped during the same period last year. By the way, the pork industry hates the name ‘swine flu.’

- Many of the millions who will visit Saudi Arabia next month for the annual pilgrimage or hajj will be met at the airport with face masks, hand sanitizer and fever checks, researchers reported today in the journal Science. The hajj attracts about 3 million people annually, and Saudi health officials have been working with CDC researchers to attempt to minimize the spread of swine flu in the close-packed holy cities of Mecca and Medina. Authorities will set up a network of hospitals and clinics linked to a central command center to diagnose cases and track outbreaks. Authorities are also urging all those who plan to attend to be vaccinated at least two weeks ahead of time. China has already announced that it will vaccinate its nearly 13,000 citizens who are planning to attend.

-- Thomas H. Maugh II