TB Infection Control

I think the risk from drink sharing is theoretically possible but very
small. Tb is largely spread by airborne spread of droplets about 1
micron or less in size which are inhaled and retained in the lungs.

This isn't an argument to not work on hygiene but I don't think is a
major contributor to Tb spread. Thx.

http://www.monitor.co.ug/artman/publish/opinions/Tuberculosis_awareness_still...

Talking about straws and risk of infection! I found this article in one of Uganda's daily that highlights some of the gaps in TB awareness. I thought I would share it even though its not a scientific paper but a journalists description of villagers who have given up on TB Control!

Moses Bateganya

I will make a short response to this question. TB is essentially an
infection of the alveolar macrophage, although it can survive and grow
in other cells and in extracellular spaces like lung cavities. Although
direct puncture wounds occasionally lead to a granulomatous lesion, the
so called "prosector's wart", infection by any route other than the
lungs is highly unusual. Here are a few statements I consider facts:

1. Sharing straws, dishes, cups etc will not transmit TB. While
drinking contaminated milk can lead to bovine TB, there is no comparable
mode of transmitting human TB.

2. Sweeping floors or shaking bed clothes in hospitals cannot re-suspend
TB organisms in a small enough particle size to be inhaled deep in the
lung and reach the alveoli. There is no need to decontaminate surfaces
from a TB control perspective - as is done in some countries.

3. Gowns and gloves are not effective in preventing TB transmission in
the laboratory or anywhere else.

The bulk of evidence over decades suggests that virtually every case of
TB is passed person to person by the airborne route only. Of course,
these modes of transmission may apply to other infections that are
droplet or ...

I will make a short response to this question. TB is essentially an
infection of the alveolar macrophage, although it can survive and grow
in other cells and in extracellular spaces like lung cavities. Although
direct puncture wounds occasionally lead to a granulomatous lesion, the
so called "prosector's wart", infection by any route other than the
lungs is highly unusual. Here are a few statements I consider facts:

1. Sharing straws, dishes, cups etc will not transmit TB. While
drinking contaminated milk can lead to bovine TB, there is no comparable
mode of transmitting human TB.

2. Sweeping floors or shaking bed clothes in hospitals cannot re-suspend
TB organisms in a small enough particle size to be inhaled deep in the
lung and reach the alveoli. There is no need to decontaminate surfaces
from a TB control perspective - as is done in some countries.

3. Gowns and gloves are not effective in preventing TB transmission in
the laboratory or anywhere else.

The bulk of evidence over decades suggests that virtually every case of
TB is passed person to person by the airborne route only. Of course,
these modes of transmission may apply to other infections that are
droplet or contact spread.


Edward A. Nardell, MD
Associate Professor
Harvard Medical School (Medicine; Global Health and Social Medicine)
Harvard School of Public Health (Environmental Health; Immunology and
Infectious Diseases)

Brigham and Women's Hospital
Division of Global Health Equity
FXB Building, 709c
651 Huntington Ave.
Boston, MA 02115

Dear Ed,
Dear colleagues,

Do we have any reference to the aerodynamic diameter/size of the
particulate mass produced in dry sweeping the floors?

Thanks and regards,
Masoud

Dr Masoud Dara
Senior Consultant
International Unit
KNCV Tuberculosis Foundation
Parkstraat 17
2514 JD The Hague
The Netherlands

More than 1.5 million people lose their lives to tuberculosis every
year. With early detection and proper treatment, most people with
tuberculosis will fully recover. Our efforts and investment in
tuberculosis control help to save millions of lives worldwide. For more
information, please visit www.kncvtbc.nl.

Re. the relative size and settling of dust vs. droplet nuclei - the
dried residua of cough-generated droplets.

There are likely many more precise modern measurements, but here is your
answer from the "bible". In Wells' 1955 text figure 5 give % particles
above a given diameter in micrometers. Course factory dust is 50% above
65 microns whereas "bacterial dust rubbed off raw material" is 50% above
20 microns. Droplet nuclei are 50% above 2.7 microns (generally
considered 1 - 5 microns).

Riley in his classic 1961 monograph on airborne infection devotes a
chapter to droplets, droplet nuclei and dust. Figure 6 shows data on
settling velocity in feet per minute from a variety of published sources
and shows that dust particles cluster around 1 to 1.5 ft per min whereas
droplet nuclei, cluster around 0.1 to 0.05 ft per min. Sedimentation
rates are a direct consequence of mass and mean aerodynamic diameter.
Not only do dust particles not remain suspended like droplet nuclei, but
if inhaled droplets or dust particles are likely to impinge on the upper
airway which is specifically designed to impact larger inhaled particles
and have them swept up the mucociliary blanket and swallowed or ...

Re. the relative size and settling of dust vs. droplet nuclei - the
dried residua of cough-generated droplets.

There are likely many more precise modern measurements, but here is your
answer from the "bible". In Wells' 1955 text figure 5 give % particles
above a given diameter in micrometers. Course factory dust is 50% above
65 microns whereas "bacterial dust rubbed off raw material" is 50% above
20 microns. Droplet nuclei are 50% above 2.7 microns (generally
considered 1 - 5 microns).

Riley in his classic 1961 monograph on airborne infection devotes a
chapter to droplets, droplet nuclei and dust. Figure 6 shows data on
settling velocity in feet per minute from a variety of published sources
and shows that dust particles cluster around 1 to 1.5 ft per min whereas
droplet nuclei, cluster around 0.1 to 0.05 ft per min. Sedimentation
rates are a direct consequence of mass and mean aerodynamic diameter.
Not only do dust particles not remain suspended like droplet nuclei, but
if inhaled droplets or dust particles are likely to impinge on the upper
airway which is specifically designed to impact larger inhaled particles
and have them swept up the mucociliary blanket and swallowed or coughed
out. While some droplet nuclei also impact on the upper airways, more
of them reach the lower airways to be engulfed by the alveolar
macrophages.

Edward A. Nardell, MD
Associate Professor
Harvard Medical School (Medicine; Global Health and Social Medicine)
Harvard School of Public Health (Environmental Health; Immunology and
Infectious Diseases)

Brigham and Women's Hospital
Division of Global Health Equity
FXB Building, 709c
651 Huntington Ave.
Boston, MA 02115

Dear Professor Nardell,
Thank you for the very useful information these data will be very important
for me in upgoinng discussions.
M. Shulgina