Health impact of handwashing
Hygiene promotion, together with improved water
supply and sanitation, is a key component of
intervention programmes which aim to reduce the
burden of diarrhoeal diseases in developing
countries. However, the impact of hygiene promotion,
and the washing of hands with soap in particular,
has wider health implications. This fact sheet
gathers the available evidence of the health impact
of the promotion of handwashing with soap in
developing countries and highlights the gaps in our
Hygiene is the practice of keeping oneself
and one's environment clean and free of
infection risk. Though many hygiene
practices can assist in preventing disease,
the one with the strongest evidence for
effectiveness and cost-effectiveness in
developing countries is handwashing with
promote handwashing with soap?
Hands are vectors that can
transport disease agents from person to person
directly or indirectly via surfaces. Hands that have
been in contact with faeces, nasal excretions and
other bodily fluids, and not subsequently adequately
washed, can vehicle large numbers of viruses,
bacteria and possibly other parasites. They can also
carry pathogens from contaminated sources such as
animal or bird faeces, contaminated foods or
domestic or wild animals to new susceptible hosts.
Handwashing is likely to be especially important
where people congregate (schools, offices), where
ill or vulnerable people are concentrated
(hospitals, nursing homes), where food is prepared
and shared and in homes, especially where there are
young children and vulnerable adults (3).
developing countries the biggest killers of young
children are respiratory infections and the
diarrhoeal disease (4) and both are preventable via handwashing. Further diseases of public health
importance for which the evidence for the impact of
handwashing is less strong are helminth and eye
infections, especially trachoma. Here we review the
evidence for the impact of handwashing on:
Diarrhoeal disease (which
can include shigellosis, typhoid and cholera)
What evidence is there for
the health impact of handwashing with soap?
Diarrhoea is a leading cause of childhood mortality
in developing countries and as a result the large
bulk of hygiene promotion studies have focussed on
the impact of hygiene promotion on the number of
diarrhoea cases. Different authors have reviewed,
with the help of meta-analysis, studies which
investigated the impact of handwashing and
handwashing with soap on diarrhoea over the last two
reviews reported a significant reduction in the risk
of diarrhoea as a result of handwashing or
handwashing with soap (Table 1). Curtis and
Cairncross (2003) estimated further that handwashing
with soap alone was able to prevent 0.5 – 1.4
million deaths per year.
Table 1: Summary of the
findings of reviews on the impact of handwashing on
the risk of diarrhoea
in diarrhoea risk
et al., 1997
et al., 2005
intervention studies / good quality studies
recently conducted randomised control trial in
Karachi, Pakistan, further confirmed the findings of
the two most recent reviews by finding an average
reduction of 45% in diarrhoea incidence when
handwashing with soap was practised (19).
Acute respiratory infection (ARI) and SARS
ARIs are the leading cause of childhood morbidity
and mortality world-wide. There are two possible
links between handwashing and ARIs:
pathogens have been identified on hands and
environmental surfaces by microbiological
especially enteric viruses, which cause
diarrhoea can also cause respiratory symptoms
recent systematic review and meta-analysis on
handwashing and respiratory infections concluded
that handwashing could cut the risk of ARIs by 16%
However the 8 studies that were found suitable
reported a range from 6% to 44% and the authors
reported that the studies were of poor quality, were
only conducted in developed countries and only one
related to severe disease. They consequently
expressed the need for more rigorous studies.
Here we update the results with two further, more
recent, studies which when all taken together, give
a pooled impact on respiratory infection of 23%
Figure 1: Risk of respiratory infection and
handwashing with soap - Rabie and Curtis 2005
review, updates with Luby et al., 2005 and Sandora
et al., 2005.
review of 10 studies conducted during the recent
SARS outbreak in South-East Asia found that
handwashing after patient care was a protective
measure against SARS infection. It needs to be noted
though that although all studies suggested a
protective effect, the pooled findings were not
found to be statistically significant (12).
c) Intestinal nematode infection
Ascariasis and trichuriasis are two of the most
common and wide-spread intestinal nematode
infections, affecting almost two billion people
world-wide (13). Fertile Ascaris and
Trichuris eggs leave humans through stool and
are directly infective in very low concentrations (1
egg could in principle lead to an infection).
Transmission occurs through ingestion. Ascaris
eggs have an especially ‘sticky’ nature and they
have been found adhered to money, agricultural
produce, cutlery, crockery and hands.
Although an association between
ascariasias-trichuriasis and handwashing with soap
seems likely and is often suggested only one single
study has investigated this (14). This study showed
no difference both in intensity and prevalence of
Ascaris infection between the two trial groups.
The study was however a short trial which did not
allow for sufficient time for reinfection, did not
control for confounding variables, including
household clustering and in general was (too)
limited in size. Other studies have included
handwashing and/or the availability of soap in the
household in their risk factor analysis. The
evidence of these studies again suggested a
protective effect but were in most cases confounded
by sanitation and socio-economic status of the
households involved (15,16,17,18).
Although there is no evidence that handwashing with
soap has an impact on the risk of schistosomiasis,
soap is known to be toxic to schistosomiasis
cercariae. There is no clear association between
hookworm infection and handwashing with soap, as
hookworm disease is caused by a larvae which
penetrates the skin in contact with contaminated
d) Eye infection
study promoting handwashing with soap on Lombok,
Indonesia, found besides a strong decrease in
diarrhoea prevalence also a significantly lower
prevalence of infective conjunctivitis.
four reviews on diarrhoea and handwashing and the
one on handwashing and ARI highlighted that many
handwashing studies had methodological short
comings, especially the older ones. Problems with
studies included one or more of the following:
was not randomized
disease data not provided
group selected / no placebo intervention
unsatisfactory definition of the outcome
control for confounding variables
measure of handwashing
High loss to
addition some studies tested the health impact of
more than one intervention. The recent large
randomized control trial in Pakistan showed that
household water treatment resulted in a 53-59%
reduction in the weekly diarrhoea prevalence and
handwashing with soap in a 45% reduction. A
combination of both interventions however resulted
only in a 50% reduction in diarrhoea (19). The
authors suggested that introducing two interventions
simultaneously does not allow their optimal combined
use as behaviour change is best achieved through
major limitation of the studies on ARIs and
handwashing with soap was that the majority of these
were conducted in developed countries and that as a
result focussed on colds and influenza. In
developing countries severe pneumonias are
responsible for the majority of ARI deaths which
makes extrapolation of the review findings to
developing countries uncertain.
What are the benefits of the use of soap?
use of soap (or other mediums like sand or ash) has
the added benefit that it increases the contact
time, facilitates friction and breaks down grease
and dirt (which contain the largest concentrations
of microbes). The use of soap in addition results in
fresh and clean smelling hands, which makes
promotion much easier. Trials in Bangladesh and
Zimbabwe showed that handwashing with soap was more
effective than handwashing with only water to reduce
faecal bacteria on hands (20, 21).
Two of the most common problems with studies that
have investigated the health impact of handwashing
with soap are:
The presence of
soap in the household has been assessed without
assessing actual use of soap. Past surveys
have shown that soap is almost universally
present in households but its actual use for
handwashing is often considerably lower (ranging
from 3% to 47%) (22).
the use of soap were investigated with the help
of a pre-designed questionnaire. The use of
questionnaires is likely to result in what the
interviewee perceives as the desirable answer
and is likely to result in an over reporting of
handwashing with soap. Structured
observations, although time-consuming and more
expensive, are the best way to assess the use of
soap for handwashing (23, 24).
There is strong evidence that handwashing with soap
can considerably reduce the incidence of diarrhoea
and ARIs in children, however, little to nothing is
known about its impact on the morbidity and
mortality of other vulnerable groups like: the
elderly and the immunocomprised.
washing with soap after defecation is suggested as
the key moment, however is this alone sufficient?
and what are the added health benefits of
handwashing with soap at other moments during the
handwashing with soap able to reduce the incidence
of skin infections and Trachoma?
in Ghana and Pakistan have shown that unhygienic
handling of food at markets resulted in a
significant contamination of vegetables and fruits.
This would indicate that handwashing with soap by
street vendors and market salesmen could have an
impact on food-borne diseases.
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