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In early 2012, experiments that made H5N1 bird flu more contagious caused an uproar. People feared that mutant viruses could escape the lab and kill people. To prevent a repeat, the government has unveiled a policy describing how scientists should study dangerous pathogens and toxins.

After researchers created versions of the bird flu virus that could spread more easily, critics began to worry that the work could spawn a pandemic if a virus escaped from the lab. After halting their work for more than a year, scientists now say the benefits outweigh the risks, and they are set to restart their experiments.

The Food and Drug Administration just approved a flu vaccine made by cells taken from the fall armyworm, an agricultural pest. The cells produce copies of a piece of the flu virus's outer coat that primes the immune system. Conventional vaccines use the whole virus and take longer to produce.

According to the latest update from the Centers for Disease Control and Prevention, the number of people age 65 and older who are getting the flu jumped sharply in the last week or so. But even though 48 states are reporting widespread activity, the agency says there are signs the flu may be easing in some parts of the country.

Flu viruses hijack the machinery inside animal cells to replicate. The theft is a complicated process that takes time. If the virus leaves the cells too early or too late, the risk of infection falls.

Influenza is especially intense this year, and people are flooding into hospitals and doctors' offices. But the flu is just one of a triple whammy of respiratory viruses — plus the nasty norovirus — that are making lots of people sick.

The earliest flu outbreak in years continues to claim victims. Businesses are taking a hit, too. They're faced with an unsolvable problem: If they tell too many sick employees to stay home, the work doesn't get done; those who do come to the office can spread germs.

As students return to class from winter break, campus health official are trying to avert an outbreak. Colleges in Boston are especially worried after the mayor's declaration last week of a public health emergency in the city.

It's still too soon to say whether this is a historically bad flu season. But it's already clear that emergency rooms around the country are filled with feverish throngs that are much larger than during the last flu season.

People expect coughs to last about half as long as they actually do. This misconception may lead patients to ask for antibiotics to treat cases of bronchitis that would go away without treatment.