by Dr. Milton Lum
Cholera is an acute diarrhoeal infection that is present in the community at all times, although its frequency may be low (endemic). It is caused by the bacterium Vibrio Cholerae and is spread by direct faecal to oral contamination or through ingestion of contaminated water and food, which is usually associated with poor management of the environment.
Whenever there is disruption of water supply and sanitation systems, there is an increased risk of the infection spreading if it is present or introduced. Person to person transmission is rare because the number of bacteria needed to cause an infection is very high.
The incubation period of cholera ranges from 2 hours to 5 days, with the common range between 2 to 72 hours. The relatively short incubation leads to an outbreak which is explosive, with many people affected in a short period of time.
Cholera affects both children and adults. Unlike other infections that cause diarrhoea, it can lead to severe dehydration, acute kidney failure and even death in a few hours. People whose immunity is impaired such as HIV/AIDS patients have a greater risk of death if infected.
Most people (about 75%) with cholera infection do not have any symptoms. Such people are called carriers. However, the bacteria remain in their faeces for 1 to 2 weeks and are shed back into the environment, which is a source of infection for other people. There has been a global resurgence of cholera in the past 5 years with more than a quarter million reported cases. The World Health Organisation (WHO) estimates that less than 10% of cases are reported to it, so its true incidence is markedly under-estimated.
The incidence of cholera in Malaysia in 2008 was 0.34 cases with mortality of 0.01 per 100,000 of the population. The current outbreak in Kelantan, Terengganu and Sabah is significant in that there are some cases which are resistant to antibiotics.
After a short incubation period, the person with cholera has an acute watery diarrhoea which is frequently associated with vomiting and muscle cramps. Because of the large amount of body fluids lost, the infected person suffers from dehydration and its complications which include changes in the body's pH.
The clinical features of cholera are different from dysentery which is often due to the bacterium, shigella. The features of this infection include frequent loose stools of small volume, consisting mainly blood and mucus. There is usually fever, abdominal pain and the urge to open the bowels, even straining, without producing stools (tenesmus). The dehydration is not as severe as that of cholera.
Campylobacter infections also cause diarrhoea. The clinical features range from a mild, self-limiting diarrhoea to severe bloody diarrhoea with high fever and bacteria in the blood stream (septicaemia). The spectrum of illness in those whose immunity is impaired especially HIV/AIDS may be relapsing or unremitting and may be accompanied by septicaemia and infections of body parts apart from the intestines.
The diagnosis of cholera is confirmed by finding the bacterium in the infected person's stools. The availability of a rapid diagnostic test has made it possible for quicker diagnosis of the infection.
The treatment of cholera is founded on prompt correction of the dehydration. This can be in the form oral rehydration salts (ORS) and/or intravenous fluids. ORS can provide adequate treatment for up to 80% of patients. However, those who have severe dehydration have to be treated with intravenous fluids.
Antibiotics are also used in the treatment of cholera as they reduce the duration of illness and the volume of body fluids lost leading to a decrease in the fluid requirements for rehydration.
Antibiotic resistance is not uncommon during cholera epidemics. There is wide variation in the patterns of antibiotic resistance at different times and different places. However, the cholera strains often become sensitive to the antibiotics that they were previously resistant to.
As the stools, vomitus and even the soiled clothes of cholera patients are very contagious, hand hygiene is crucial to preventing its spread. The hands have to be washed systematically with soap and water or disinfectants before and after providing care on every occasion. They also have to be washed after defaecation and before handling food or eating. Food has to be prepared and kept in a hygienic manner. The toilets and other water containers used by infected patients have to be washed with disinfectants. The patients are usually isolated from other patients to prevent spread.
The preventive measures in cholera outbreaks primarily involve the provision of clean water and proper sanitation to those who are likely to be affected. Health education and good food hygiene play an important role, especially hand hygiene. This requires the commitment and active participation not only from health care staff but also other sectors including water provision, sewage disposal, education and information.
There are cholera vaccines available. The oral vaccine is suitable for those who are travelling to an area where cholera is endemic. The 2 doses of the oral vaccine, of which there are 3 types available, are taken 10 to 15 days apart. The protection provided ranges from 65 to 85%. Although it has recently been used in mass vaccination, there is no convincing evidence that it provides long-term protection. The use of the injectable vaccine is limited as its efficacy is low and the risk of adverse reactions is high.
The prescription of antibiotics to all members of a community in which there is an outbreak does not affect its spread. Instead, it can create a false sense of security and may pose problems like development of antibiotic resistance.
More info on CHOLERA here.
by Dr. Milton Lum