With Swine Flu Returning, Families Can Reduce Risk of Transmission
Tuesday, September 8, 2009
Last winter, a few months before the first outbreak of H1N1 flu, my 13-year-old became ill, first with a cough and runny nose, and then with low-grade fever and nasal congestion. It was not severe enough to have her miss school, but we had her skip indoor soccer practice. A week later her older sister, who shares her room, had the same constellation of symptoms; then my wife and my youngest son. Over a three-week period I carefully tracked the passage of the virus within the family.
This is nothing new for me. I'm an infectious-disease doctor, and a standard question for my patients is: "Is anyone else in the family sick?" The home is always prime territory for sharing disease. But the resurgence of swine flu as summer ends -- already my hospital is admitting two or three cases a day -- has made me reexamine just how viruses spread, as well as what we can do about it.
The H1N1 flu virus, like the seasonal influenza virus and like most other cold viruses, travels by three major routes: close-contact respiratory droplets, the surface of inanimate objects and hand-to-face transfer.
Let's consider the droplets: You've probably seen one of those high-speed photographs of a person coughing or sneezing, emitting a spray of viral particles resembling the Milky Way. A percentage of those droplets remain in the air long enough to find their way to the nasal passages of anyone within three to six feet of the sneezer. The percentage varies with temperature and humidity: Peter Palese of the Mount Sinai School of Medicine in New York says that close-contact studies using guinea pigs -- which are susceptible to infection from human flu viruses -- found that the flu virus was transmitted almost 100 percent of the time in situations where the temperature was below 41 degrees and the relative humidity was below 50 percent.
That's a good reason to sneeze and cough into our tissues, elbows or shoulders, even though the infection rate drops in warmer, more humid environments.
The droplets can also land on shared surfaces such as a dining table, sofa or computer keyboard. How long the virus remains infectious depends on several circumstances: It lasts longer on a stainless-steel tabletop than on cloth or tissue, for example.
"Because there are a number of factors, such as temperature and presence of mucus, involved, there is a wide range of time that a virus can persist outside the body," said Matthew J. Arduino of the coordinating center for infectious diseases at the Centers for Disease Control and Prevention. "Generally speaking, influenza viruses can persist for 24 hours to seven days on a nonporous surface."
At my hospital, an infectious-disease doctor was convinced he caught a virus from the keyboards in the intensive care unit. So at our house, once the viral illness hit, I routinely wiped the keyboard clean with an alcohol swab.
The other route for viral infection is the hands touching the eyes, nose and mouth. Most of us frequently touch our faces: We put things in our mouths, rub our eyes or noses, lick a finger to turn a page, adjust our glasses. I was unable to find any data on how often we do such things, so at a recent meeting with five people at my local medical society, I decided to keep a private tally. Over a five-minute period I counted 17 hand-to-face touches, a rate of about 40 touches per person per hour. At another time, during a hospital training session, I did spot checks on 10 people every 10 minutes. I noticed that at any given check, three or four people were touching their hands to their face. Obviously, our hands are key to transmission of viruses and bacteria.
But what can we do about it? In the hospital, I use sanitizer on my hands and wear gloves for every patient encounter. At home, during the viral outbreak, I was meticulous in my hand washing and insisted on the kids' doing the same. I know you're tired of hearing about hand washing, but there is strong evidence that it works: In one Detroit study, schoolchildren who washed their hands four times a day had 21 percent fewer sick days due to respiratory illness than did students in general, and 57 percent fewer days lost due to upset stomachs.
Once someone in the home has the flu, CDC guidelines suggest that, among other precautions, that person should wear a mask "if available and tolerable."
There are two main types of masks: the common, soft surgical or dust mask, and the tight-fitting N95 mask, which screens about 95 percent of small droplets. At the hospital, where we use N95s, we find them effective but uncomfortable and even suffocating after a few minutes. I don't recommend them for household use.
The soft surgical masks, though less protective, also offer some clinical benefit. In a 2009 study involving sick schoolchildren in Australia, the use of soft masks reduced the risk of acquiring infection by 60 to 80 percent. Given that the soft mask does not screen all the viral droplets, I suspect some of the protection from the masks came from preventing hand-to-face contact.
If H1N1 or a severe flu virus got into my home, I would not hesitate in masking myself or members of my family. But during our viral infection earlier this year, I decided against it, mainly because the disease was quite mild.
I did choose to practice "social distancing." I slept in the guest bedroom for a few nights when my wife was ill; she understood. We banned our 10-year-old son from crawling into bed when he was coughing; he pouted. All hugs were on hold, which did not sit well with our teenage daughters. We didn't share drinks.
Taking precautions reduces, but does not eliminate, the chance of infection. Ironically, as the disease went through my family, the fact that I remained healthy began to make me feel guilty and a little left out. After three weeks, I began to wonder: Was I not really close to these people I love? Or, with a little bit of magical thinking, was the virus avoiding me out of some kind of professional courtesy?
A few days later I woke up with a sore throat, nasal congestion and a low-grade fever. It actually felt good to feel bad.
Manoj Jain is an infectious-disease specialist in Memphis and an adjunct assistant professor at the Rollins School of Public Health at Emory University in Atlanta. Comments: firstname.lastname@example.org.