Level of risk during consultation of TB/MDR TB patients/droplet transmission?
Started by Ana Serralheiro on 20 Jan 2010
Dear all,
I'm wondering about the risk of a Health-care worker consulting 5 to 6 TB/MDR TB patients per day in an OPD clinic if we consider that is a well ventilated room; patient is located 1 meter from the health care worker and is protecting the cough?
Also, "how much" is TB transmitted through droplets in comparison to airborne? According to some discussion already in GHD is not transmitted through the GIT (e.g. sharing spoon, etc). So then how high is the risk through the mucosa (e.g. droplet emitted when patient is coughing in front of the HCW)?
Is there any bibliography on this?
Thank you
Ana
Ana Serralheiro
Infection Control Specialist
MSF Switzerland
Swaziland Mission
Keywords: Articles, General Resources, TB IC Guidelines, Technical Consultants
Edward Nardell, MD
Hi Ana,
There is no easy answer to quantifying risk in any given situation. We can say that seeing MDR-TB patients does pose a risk of transmission. The biggest variable is source strength which varies greatly from patient to patient. In our studies, those of Escombe, and those of Riley, very few patients infected most of the exposed guinea pigs. Epidemiology studies suggest that the same is true in human to human transmission. Except for rare inoculations in the lab, ALL TB is spread by droplet nuclei (airborne) because organisms MUST reach the deep lung to come into contact with alveolar macrophages, the place they are adapted to replicate in the human body. Large droplets are highly unlikely to cause any infections at all. No infection of mucosal layers of eyes or mouth. Close contact, however, puts the worker in the area where the concentration of airborne droplet nuclei is higher. There is a lot written on transmission, but no handy bibliography.
I will post a review on GHDonline.
Ed Nardell, MD
2:48 PM, 21 Jan 2010 | Permalink
Ana Serralheiro
Hi Ed,
Thank you for your answer. Yeah the risk depends from each situation, number of patients, practices at the Health facility, etc.
My question comes because we are presently working on a policy for using of respirators because there’s an increasing tendency to overuse them. We are presently discouraging the use at OPD, medical wards, etc. and reinforce on administrative and environmental measures.
According to your answer droplet precautions will then be necessary because TB is only transmitted through droplet nuclei (airborne). So, only airborne precautions?
When it comes to write the policy and discourage the staff on their use this is important because we have to provide clear and consistent information on this...
Thank you
Ana
12:49 PM, 22 Jan 2010 | Permalink
Edward Nardell, MD
Hi Ana,
While I cannot comment on your specific risk setting, I am afraid that I have to disagree with your recommendation to discourage use of respirators when dealing with MDR patients in the OPD, medical wards, etc. The reason that we recommend respirators at all is that neigher administrative controls nor environmental measures are entirely effective. A respirator is one more fail-safe mechanism to protect the worker when confronted with an unsuspected TB case under conditions conducive to transmission.
We must not confuse droplet spread (contact) with droplet nuclei spread (airborne). I can see how it could be confusing. Droplet nuclei are the dried residu of larger droplets that become airborne. All TB is essentially spread by the airborne route, not by contact with larger respiratory droplets. Therefore, respirators are an important part of airborne infection control. All international recommendations for TB will be consisetent on this matter.
Ed Nardell, MD
4:02 PM, 22 Jan 2010 | Permalink
Ana Serralheiro
Hi Ed,
Thank you once again for your clarifications.
the staff is presently being teach accordingly on the differences between Droplet and airborne trnamission. But I agree with you that can be confused when we are talking about the PPE that should be used.
Following the recommnedations form CDC on on the use of "Respiratory Hygiene/Cough Etiquette in Healthcare Settings" (droplet precautions at http://www.cdc.gov/flu/professionals/infectioncontrol/resphygiene.htm) under "Management of Persons with Symptoms of TB Disease" (http://www.cdc.gov/tb/NewsandAnnoucements/FacilityGuidance.htm); why is it advised to "observe Droplet Precautions (i.e., wearing a surgical or procedure mask for close contact), in addition to Standard Precautions, when examining a patient with symptoms of a respiratory infection, particularly if fever is present (...)"?
This is applied to influenza but shouldn't the N95 be advised when examinating a patient with symptoms of a respiratory infection/TB suspect (airborne precaution) instead of surgical mask (drplet precaution)?
Thank you
Ana
1:17 PM, 1 Feb 2010 | Permalink
Ana Serralheiro
Hi Ed,
Thank you once again for your clarifications.
The staff is presently being teach accordingly to your clarifications on the differences between Droplet and Airborne transmission. But I agree with you that can be confused when we are talking about the PPE that should be used.
Following the recommendations from CDC on the use of "Respiratory Hygiene/Cough Etiquette in Healthcare Settings" (droplet precautions at http://www.cdc.gov/flu/professionals/infectioncontrol/resphygiene.htm) under "Management of Persons with Symptoms of TB Disease" (http://www.cdc.gov/tb/NewsandAnnoucements/FacilityGuidance.htm); why is it advised to "observe Droplet Precautions (i.e., wearing a surgical or procedure mask for close contact), in addition to Standard Precautions, when examining a patient with symptoms of a respiratory infection, particularly if fever is present (...)"?
This is applied to influenza but shouldn't the N95 be advised when examinating a patient with symptoms of a respiratory infection/TB suspect (airborne precaution) instead of surgical mask (droplet precaution)?
Thank you
Ana
1:21 PM, 1 Feb 2010 | Permalink