Airborne Pathogens: Elusive and Dangerous

The study of airborne pathogens is complex, but people of every education level know that air quality is important, and that germs let loose in the air can lead to infection of millions of people. Indeed, the issue of air quality and safety is widespread, says Jeffrey Cirillo, PhD, associate professor in the Department of Microbial and Molecular Pathogenesis at Texas A&M University System Health Science Center.

“I believe that the average person is aware of the importance of air quality because it is an issue that everyone discusses on a daily basis — smog reports, environmental protection, infections in air,” Cirillo said. “In my discussions with people it seems clear that everyone understands that if you can’t breathe, you are in trouble.”

The threat of airborne pathogens should be taken “very seriously” because air is the most efficient route by which pathogens can gain access to a large number of people, according to Cirillo. “Epidemic-causing pathogens can often spread by the airborne route for just this reason and efficiency of transmission is one of the most important characteristics that should be considered when evaluating how large an impact infectious diseases can have,” he adds.

One of the primary tools to prevent the spread of airborne pathogens in healthcare facilities is the use of negative air pressure. Negative air pressure regulates environments. By using a negative pressure containment field, such as a portable anteroom, healthcare staffs can prevent harmful pathogens from escaping an airborne infection isolation room, or from ceiling cavities during maintenance work, says John Pierson, product manager for Fiberlock Technologies. “This ability is critical in the event of a sudden influx or surge of patients,” Pierson says. “In fact, the federal government uses the ability of a facility to deal with a surge of patients as one criterion for Health Resources and Services Administration funding.”

Disastrous Proportions

Determining which airborne pathogens are most likely to cause a pandemic event is no easy feat.

“The great unknown is the issue here,” Pierson says. “We truly don’t know what pathogens are more likely to be the cause of a biological disaster. Experts are currently looking at H5N1 very closely as a candidate for pandemic due several of its genetic traits, but the threat of biological agents such as smallpox, anthrax and botulinum being used as weapons complicate the matter.

“There is the possibility that a genetically altered organism used for bio-terror could dramatically alter the playing field in regards to treatment and prevention,” he adds. “The reality could be that a large number of people could, without warning, need to be hospitalized and isolated from other patients. Regardless of the organism, airborne infection isolation would be essential to preventing the spread of disease during this type of event.”

Use of personal protective equipment (PPE) helps reduce the spread of pathogens, and is even more important than usual in a disastrous event. However, PPE is not the end all be all, according to Jeffrey Birkner PhD, CIH, vice president of technical services for Moldex-Metric, Inc.

“Addressing pandemic and emergency airborne pathogen threat response issues must be all encompassing and does not only deal with PPE,” Birkner says. “In addition, administrative and engineering controls must be considered first. PPE, while extremely important, is actually the medical facility’s and staff’s last line of defense to an airborne pathogen threat.”

Two of the major concerns regarding emergency preparedness for a pandemic event include a facility’s surge and isolation capacity, says Gary Messina, principal and CEO of Biological Controls. Messina has more than 30 years experience in the field of high-efficiency filtration and design and manufacture of airborne infection control equipment.

“The Centers for Disease Control and Prevention recommends that hospitals establish isolation rooms maintained under negative pressure,” Messina says. “But most hospitals have a tiny fraction of isolation rooms available compared to the total room count. And at any one time these rooms may already be occupied, which further reduces the availability to isolate individuals entering through the surge. Since many hospitals operate at near capacity levels currently, the addition of undiagnosed patients arriving for treatment in a disaster event poses the question of accommodating a huge surge of individuals requiring both beds and isolation areas. This does not take into account the regular patient load seen everyday at every hospital and medical facility.”

That’s not a pretty picture, but it’s one for which every facility must prepare. Another threat related to airborne pathogens is mold, especially during and after certain disasters, such as floods or hurricanes. In humid areas mold can be a “huge concern” says Grant Rowe, respiratory protection product manager for Bullard.

“The good news is that airborne precautions and contact precautions are very effective regardless of the specific pathogen,” Rowe says. “It is important to understand that some infections can enter in through the eyes (such as mold) and an N-95 mask will not be sufficient; tight fitting goggles, a full face respirator, or a PAPR (powered air purifying respirators) with a loose fitting face piece or hood would be more appropriate in these situations.”

Prevention and Containment

As the old saying goes, an ounce of prevention is worth a pound of cure. In order to prevent airborne pathogen transmission — especially influenza — healthcare staffs should ask and seek answers to certain questions, especially regarding influenza, says Edward Fries, a spokesperson for the NIOSH National Personal Protective Technology Laboratory, which is part of the National Institute for Occupational Safety and Health (NIOSH).

These questions include:

What are the major modes of influenza transmission?

What are the relevant sizes of aerosols?

What is the infectivity of aerosols?

How does air flow exchange and ventilation affect transmission?

What is the effectiveness of medical masks?

What is the role of fomites?

Should PPE other than respirators be certified? If so, who would be responsible for certification?

“Controlling the spread of a potential influenza pandemic is of critical importance to the more than 14 million healthcare workers in the United States (approximately 10 percent of the U.S. workforce) and their patients,” Fries wrote in a NIOSH blog. “Given that healthcare workers will be on the front lines during an influenza pandemic, protecting them with the best available prevention methods and PPE is imperative to reducing illness and death and preventing the progression of a pandemic.”

The basic steps that medical facilities should take to contain airborne pathogen exposure involve having the necessary equipment on site, and making certain that personnel are properly trained to deal with a wide range of possible threats well in advance, Birkner says.

He believes that for respiratory protection, every facility should have an adequate stockpile of NIOSH-certified N95 respirators or comparable equipment. Every employee should have one. Guidance on the size of the respirator stockpile and other useful pandemic preparation information can be found at:

“Although this document has not been finalized, it has some good information that medical facilities can use to help them prepare,” Birkner adds.

Improper or lacking respiratory protection can be life threatening, says Michael Wang, marketing manager for Bio-Medical Devices Intl. “Purchasers seeking protection for their workers should not be satisfied by minimum protection, and should seek better than the least that is recommended by regulatory agencies,” Wang says. These devices are most useful when healthcare workers (HCWs) know how to use them. “...conduct yearly refresher respirator usage courses for your HCWs so in the event of a pandemic, HCWs are least likely to be in a ‘panic’ mode and remember how to use their respirators properly and effectively,” Wang says.

Proper fitting of respiratory devices can be accomplished through various equipment. For instance, the PORTACOUNT® PRO+ respirator fit tester by TSI can improve risk management programs, according to Tonya Foucault, a spokesperson for TSI.

Of course, if air is clean in the first place respiratory devices aren’t as necessary. Overall air quality can be improved in most settings by maintaining a high number of air exchanges per hour (proper air flow characteristics), proper maintenance of equipment and filters, adequate humidity and consistent air quality monitoring and testing, Cirillo says.

“Healthcare workers can be better prepared for the threat of airborne pathogens through continuing education in infectious diseases, maintaining vigilance regarding normal versus abnormal frequencies of such infections in their setting and ensuring that they are prepared with the proper equipment and training for respiratory crises should they occur in patients,” he adds.

Evaluation of whether patients should be isolated should be done as early as possible to prevent spread of infection from person to person, and sterile technique should be adhered to, including proper use of PPE, Cirillo says.

“It is one thing to treat patients, but how does one receive treatment if all of the healthcare workers are also becoming ill?” Cirillo asks. “It is extremely important that healthcare workers become aware of any outbreak early, communicate with all other healthcare facilities and personnel immediately and help to prevent spread within the healthcare facilities themselves where there are likely to be a high concentration of infected individuals.”

Furthermore, healthcare workers should be vaccinated against as many potential threats as possible, and after an outbreak, it is “most important” that the facilities are properly decontaminated before any uninfected person is admitted, he adds.


The right equipment is rendered almost useless if it is not cared for and inspected. Fortunately, there are several ways a facility can maintain the highest level of equipment preparedness regarding airborne pathogens, Pierson says.

He recommends “methodical and regimented” inspection of all pre-filters and high efficiency particulate air (HEPA) filters in permanent heating, ventilation and air conditioning (HVAC) systems. He also suggests that portable mobile containment units should be kept in strategic areas of the facility along with negative air machines to provide HEPA-filtered negative pressure. “Staff should be aware of these locations and should be trained to construct, move and set airflow (for the unit),” Pierson says.

He also believes that surface disinfectants that are registered by the Environmental Protection Agency should be used regularly on touch points. “Training materials, signs and other printed materials indicating procedures may be helpful as reminders between training exercises,” he adds.

It’s frightening any time an infectious agent makes its way around a healthcare facility, and when this occurs, all departments must work in tandem.

“The ability to quickly isolate patients without moving them from their patient or treatment room is a tremendous asset when dealing with a potentially deadly disease, and while having the appropriate tools ... in place is critical, a response plan should also be worked out and rehearsed,” Pierson says.

“Each part of the infection control response team should know their part and be able to perform it quickly in the event of an emergency,” he adds. “A facility may want to set up mock situations in which temporary isolation must be set up, or a sudden surge of patients flood the ER (emergency room). Staff should understand the importance of patient isolation and be able to set up equipment properly.”

Q & A: Respiratory Industry Insiders

Offer Airborne Pathogen Advice

Grant Rowe, respiratory protection product manager for Bullard, and Michael Wang, marketing manager for Bio- Medical Devices Intl., took part in an Infection Control Today Q&A about prevention and containment of airborne pathogens.

1. How should medical facilities prevent the spread of airborne pathogens? What steps should be taken?

Rowe: I am not a nurse, a doctor, healthcare worker, or even a facility designer but I can give you my perspective as a respiratory protection manufacturer and as someone who actively participates with APIC (Association for Professionals in Infection Control and Epidemiology) and AOHP (Asthma Health Outcomes Project). First, patients need to be quickly diagnosed and isolated. This doesn’t mean that the exact ailment must be determined immediately but a decision should be made very quickly if a patient should be moved to isolation. The isolation room is typically negative pressure which means that air from inside the room cannot escape due to pressure difference. It will also have ventilation with HEPA (high efficiency particulate air) filtration that completely removes and replaces the air many times per hour. 

Next, anyone that comes in contact with patients suspected to have a potentially contagious infection that can be spread via airborne pathogens should take airborne precautions, and many times must also take contact precautions.

The specifics of these are spelled out by the CDC (Centers for Disease Control and Prevention) but they call for a NIOSH approved respirator such as an N-95 mask or higher protection. It is important to understand that a surgical mask is not a respirator and provides no protection against airborne pathogens. A surgical mask only prevents droplets from the healthcare worker reaching the patient. A respirator prevents airborne particles from reaching the healthcare worker. It is also important to understand that an N-95 mask is a tight fitting respirator that requires annual fit testing of the healthcare worker. In years past, OSHA did not enforce this but the Wicker Amendment has expired and enforcement is now in effect.

In addition, facial hair is not allowed when wearing a tight-fitting respirator such as an N-95 mask. Furthermore, it is important to be aware that there are respirators that do not require fit testing. PAPRs when worn with loose-fitting face pieces or hoods do not require fit testing. This is because air is constantly flowing into the respirator and effectively pushing out contaminants that may try to enter through the loose seal. This type of respirator actually provides higher protection than an N-95; PAPRs carry an assigned protection factor (APF) of 25 or 1000 (depending upon the head top) while an N-95 mask only carries an APF of 10. For more about assigned protection factors go to

Finally, training must be done early and often. Too often I hear about a hospital receiving HRSA (Health Resources and Services Administration) grant money and buying respirators that get locked up in a remote storage location never to be heard from again. The danger here is that when the protective equipment is needed it will be too inaccessible and used improperly.

Wang: Respiratory protection, or the lack thereof, can obviously be life threatening. Purchasers seeking protection for their workers should not be satisfied by minimum protection, and should seek better than “the least” that is recommended by regulatory agencies. The US Department of Labor says, “NIOSH-approved disposable particulate respirators (e.g., N95, N99, or N100) are the minimum level of respiratory protection that should be worn.” NIOSH (National Institute for Occupational Safety and Health) also says that, “Surgical masks are recommended only as a last resort for health care and medical transport workers exposed to SARS patients when no NIOSH-approved respirator equivalent to or greater than the N-95 is available.”

Key respirator qualities and characteristics that would provide proper respiratory and contact protection as well as be safely and conveniently compatible with a wide range of working environments to allow cost effective, full scale implementation, would include ≥ 99.97 percent filtration efficiency, approved by NIOSH (minimum HEPA level efficiency); universal fit — not necessary to fit test users so they are usable by any employee and may be shared with proper decontamination between uses; reusable to provide long term cost effectiveness; be free of bulky, weighty, or extending apparatus so as to not impede aggressive and agile movements as may be required in the work environment; be comfortable and convenient to the wearer to facilitate use compliance; be rugged and reliable for routine, daily use and for extended periods during emergencies; provide visual indication of filtering and operation effectiveness and safety.

Upon close examination, implementing a PAPR- (Powered Air Purifying Respirator) based infection control program for your HCWs (healthcare workers) can be both an increase in HCW safety as well as an advantage to the bottom line.

In addition, some facilities have considered assigning HCWs, who have a high risk of exposure to airborne pathogens, a PAPR to take home to minimize the likelihood of absenteeism in the event of a pandemic.

Lastly, conduct yearly refresher respirator usage courses for your HCWs so in the event of a pandemic, HCWs are least likely to be in a “panic” mode and remember how to use their respirators properly and effectively.

2. In a physical disaster or a pandemic event, what airborne pathogens are most likely to cause problems, and how should they be treated?

Rowe: At present pandemic flu is the most likely danger. Experts are somewhat divided over whether the question is a matter of if or when the next pandemic will occur, but history has shown that there is a definite trend pointing to a pandemic in our near future. Other concerns are TB which appears to be patients that actually contracted it years ago and are having flare ups in the present day. Mold is a huge concern especially in areas where flooding or humidity can be heavy. The good news is that airborne precautions and contact precautions are very effective regardless of the specific pathogen. It is important to understand that some infections can enter in through the eyes (such as mold) and an N-95 mask will not be sufficient; tight-fitting goggles, a full face respirator, or a PAPR with a loose-fitting face piece or hood would be more appropriate in these situations. 

Wang: In a physical disaster or a pandemic event airborne pathogens such as TB, SARS, Bird Flu (H5N1), Anthrax, mold/fungus, and other contagious elements expelled from buildings, underground, and other closed areas which can house such contaminants, may cause serious public health damage.

Please refer to your facility or CDC guidelines for proper treatment procedures.

An easy and obvious “preventive” measure is to properly wear a respirator during and after the incident. In addition, make sure your eyes are covered/protected with goggles. Thus, making MAXAIR an ideal choice of respiratory, head, face, and neck protection in the event of a physical disaster or a pandemic.

3. What materials should every healthcare facility have on hand to prevent airborne pathogen transmission?

Rowe: Signage, educating visitors, patients, contractors, vendors, and healthcare workers. Respirators, negative pressure isolation rooms, plans to handle surges including stockpiles of PPE (personal protective equipment), emergency surge capacity shelters and educational materials.

Wang: Respirator and surgical masks are most commonly used to prevent airborne pathogen transmission. However, more and more attention is being directed toward the use of PAPRs.

Why? The principle purpose of a surgical mask is to protect the surgical field and others (patients) from the spread of droplets from the users. Additionally, surgical masks may be used for user protection from splash during surgery.

A larger concern about surgical mask protection for a HCW is that they are typically not designed to make a seal against the face of the wearer. Without a good seal, their protection against viral and bacterial contaminants is poor.

Even N95 respirators are receiving greater scrutiny relative to their ability to provide cost effective bacterial and viral protection due to their low-filter efficiency and need for fit testing verification for each individual, for each brand and style of respirator, annually.

Fit testing is accomplished by qualitative as well as quantitative protocols. Qualitative fit testing is perhaps the easiest and fastest means of fit testing. The results are along the lines of “you get what you pay for” as results are variable.

Quantitative fit testing requires more technical skill and $10,000-$20,000 of test equipment.

The main concern about fit testing is that even when done properly and accurately, the HCW is only assured of a good fit for the masks that were used during the testing. Once they leave the test area, putting on another mask is another fitting episode. Is it done by the individual the same way each time, under the pressing conditions of the infected patient care regime? If not, disaster can happen as it did in Toronto during the SARS epidemic.

Also, masks, N95 and surgical, can not be fitted to HCWs with facial hair and other variables in facial shape, such as scars, large weight gain or loss, etc.

Even with a secure fit, the inherent filtering efficiency is less than PAPRs.

FDA (U.S. Food and Drug Administration) does not test surgical masks as they do respirators. Surgical masks are rated by the manufacture, and their reported particle filtration efficiencies, e.g., >95 percent, may be considerably higher values than what would be obtained using NIOSH N-95 test methods, e.g., as low as 70 percent.

Similarly, the maximum, ideal filtration efficiency of an N95 respirator is only guaranteed to be 95 percent. That means that with an excellent fit, 5 percent of the contaminant has to be expected to get through.

PAPRs (helmet-style respirators) use inherently higher efficiency filters than either surgical masks or N95 respirators. And, they are positive pressure respirator systems so they do not require fit testing. Also, they are reusable and are used interchangeably between HCWs, with appropriate decontamination between uses.

Masks and N95s are negative pressure devices. When the user inhales they create negative pressure within the mask that will suck in contaminated air anywhere there is an incomplete seal with their face. This is why a perfect seal, or fit, is so crucial.

PAPRs on the other hand, are positive pressure devices. For example, the MAXAIR System blower pulls the contaminated air through high efficiency filters, with from 99.97 percent to 99.997 percent filtering efficiency.

Now only .03 percent to .003 percent of the contaminant may get through. That is at least 150 to 1,500 times less than a mask.

The MAXAIR blower pulls in air, filters it, and passes it gently down in front of the face at a user selectable 6 CFM to 9 CFM. This provides sufficient air for all working conditions, and it provides an automatic cooling effect to the user.

More importantly, the high volume of air flow creates a positive pressure within the helmet so that the HCW can not pull in contaminated air from around the facial seal. This is the reason PAPRs do not require fit testing.

Another benefit of the PAPR air flow control is that is makes breathing as natural as if the HCW wasn’t wearing a respirator at all. This is not the case with masks as they present resistance to breathing.

Just as a leading healthcare institution published in 2005, you can achieve both better respiratory protection and a long term cost advantage with a non conventional PAPR solution such as MAXAIR.