Bacteria Counts Spike When We Are In The Room

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A person's mere presence in a room can add 37 million bacteria to the air every hour - material largely left behind by previous occupants and stirred up from the floor - according to new research by Yale University engineers.

"We live in this microbial soup, and a big ingredient is our own microorganisms," said Jordan Peccia, associate professor of environmental engineering at Yale and the principal investigator of a study recently published online in the journal Indoor Air. "Mostly people are re-suspending what's been deposited before. The floor dust turns out to be the major source of the bacteria that we breathe."

Many previous studies have surveyed the variety of germs present in everyday spaces. But this is the first study that quantifies how much a lone human presence affects the level of indoor biological aerosols.

Peccia and his research team measured and analyzed biological particles in a single, ground-floor university classroom over a period of eight days - four days when the room was periodically occupied, and four days when the room was continuously vacant. At all times the windows and doors were kept closed. The HVAC system was operated at normal levels. Researchers sorted the particles by size.

Overall, they found that "human occupancy was associated with substantially increased airborne concentrations" of bacteria and fungi of various sizes. Occupancy resulted in especially large spikes for larger-sized fungal particles and medium-sized bacterial particles. The size of bacteria- and fungi-bearing particles is important, because size affects the degree to which they are likely to be filtered from the air or linger and recirculate, the researchers note.

"Size is the master variable," Peccia said.

Researchers found that about 18 percent of all bacterial emissions in the room - including both fresh and previously deposited bacteria - came from humans, as opposed to plants and other sources. Of the 15 most abundant varieties of bacteria identified in the room studied, four are directly associated with humans, including the most abundant, Propionibacterineae, common on human skin.

Peccia said carpeted rooms appear to retain especially high amounts of microorganisms, but noted that this does not necessarily mean rugs and carpets should be removed. Extremely few of the microorganisms commonly found indoors - less than 0.1 percent - are infectious, he said.

Still, understanding the content and dynamics of indoor biological aerosols is helpful for devising new ways of improving air quality when necessary, he said.

"All those infectious diseases we get, we get indoors," he said, adding that Americans spend more than 90 percent of their time inside.

Study Shows First N.C. Case Of Feral Pig Exposure To Brucella suis Bacteria

A North Carolina State University study shows that, for the first time since testing began several years ago, feral pigs in North Carolina have tested positive for Brucella suis, an important and harmful bacteria that can be transmitted to people.

The bacteria are transmitted to humans by unsafe butchering and consumption of undercooked meat. Clinical signs of brucellosis, the disease caused by the bacteria, in people are fairly non-specific and include persistent flu-like symptoms. The bacteria can also spread in pig populations, causing abortions in affected swine.

In a study conducted to test N.C. feral pig populations for several types of bacteria and viruses, about 9 percent of feral pigs studied in Johnston County and less than 1 percent of feral pigs surveyed randomly at 13 other sites across the state showed exposure to B. suis.

Dr. Chris DePerno, associate professor of forestry and environmental resources at NC State and the corresponding author of a paper describing the research, says the results are troubling for people who hunt feral pigs for sport or food.

"Now that exposure to Brucella suis has been found in North Carolina's feral pig populations, people need to take care when hunting, butchering and cooking feral pigs," DePerno says. "That means wearing gloves when field dressing feral pigs and cooking the meat to the proper temperature."

Dr. Suzanne Kennedy-Stoskopf, an NC State research professor of wildlife infectious diseases and a co-author of the paper, says that testing positive for antibodies to B. suis. means the feral pigs have been exposed to and mounted an immune response against the bacteria. Antibodies do not eliminate B. suis. from pigs, so the animals are considered infected and capable of transmitting the bacteria to other pigs and people. She adds that control and eradication programs introduced in the late 1990s eliminated swine brucellosis from all commercial pig populations in the United States.

Kennedy-Stoskopf says that B.suis can be transmitted among pig populations when pigs ingest infected tissue or fluids. Direct contact with infected pigs or ingestion of contaminated food and water could cause currently uninfected pig populations to become infected.

"Spillover from infected feral pigs to commercial pigs is an economic and a public-health concern," Kennedy-Stoskopf says. "The biggest public-health risk is to pork processors and hunters who field dress feral pigs. Although cases of brucellosis are rare in the United States, people need to understand the clinical signs - like intermittent fevers and persistent headaches - and go to the doctor for diagnosis and treatment if they have these flu-like symptoms." Because clinical signs are so non-specific, it is important to tell your physician if you have had any exposure to feral swine carcasses and meat.

Feral pig populations are exploding across the country, DePerno says. Besides the rabbit-like reproductive proclivity of feral pigs, people are partially responsible for the population boom. There is strong evidence that humans have transported feral pigs into new areas for hunting.

"Control of feral pig populations is difficult at best," DePerno says. "Research indicates that about 70 percent of the population will need to be removed each year to keep a wild population stable. Regarding feral pigs, hunting usually removes from 8 to 50 percent of a given wild population."

Feral pigs can be destructive to the environment and can outcompete native animals. They dig, root and tear up crop lands; eat just about anything; and can spread disease to animals and people.

DePerno hopes that more research on how far feral pigs travel - and increased scrutiny of hunters who move feral pigs from place to place - will help keep feral populations from spreading.

NC State graduate student Mark Sandfoss and postdoctoral researcher Dr. Maria Palamar conducted research and co-authored the paper, which is published in the Journal of Wildlife Diseases. Researchers from the U.S. Department of Agriculture and Rollins Animal Disease Diagnostic Laboratory contributed to the research.

The study was funded by NC State's Fisheries, Wildlife and Conservation Biology Program and the Department of Forestry and Environmental Resources; the Howell Woods Environmental Learning Center; and the U.S. Department of Agriculture/APHIS/Wildlife Services National Wildlife Disease Program.

"A Serosurvey of Feral Swine (Sus scrofa) in Eastern N.C."

Authors: Mark R. Sandfoss, Christopher DePerno, Maria B. Palamar, and Suzanne Kennedy-Stoskopf, North Carolina State University; Carl W. Betsill. USDA-APHIS-Wildlife Services; Gene Erickson, Rollins Animal Disease Diagnostic Laboratory
Published: April 2012 in Journal of Wildlife Diseases

Abstract: As feral swine (Sus scrofa) populations expand their range and the opportunity for feral swine hunting increases, there is increased potential for disease transmission that may impact humans, domestic swine, and wildlife. From September 2007 to March 2010, in 13 North Carolina counties and at Howell Woods Environmental Learning Center, we conducted a serosurvey of feral swine for Brucella suis, pseudorabies virus (PRV), and classical swine fever (CSF); also, the samples obtained at Howell Woods were tested for porcine circovirus type 2 (PCV-2). Feral swine serum was collected from trapped and hunter harvested swine. For the first time since 2004 when screening began, we detected B. suis. antibodies in 9.2% (9/98) of feral swine at Howell Woods and
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