Published on November 1, 2007
Old Diseases Still New: Old Diseases Still New There are many terrible diseases, that devastated the old world, still with us. We will go through three such diseases: Plague Cholera Tuberculosis There are many others Cholera: Cholera Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. The disease has a short incubation period, from less than one day to five days. The bacterium produces an enterotoxin which causes a copious, painless, watery diarrhea and which can quickly lead to severe dehydration and death if treatment is not promptly given. When cholera appears in a community it is essential to ensure: hygienic disposal of human feces, an adequate supply of safe drinking water, and good food hygiene. Cholera has reemerged as a global health threat after virtually disappearing from the Americas, most of Africa, and Europe for more than a century. Vibrio cholerae bacteria showing the characteristic comma shaped body and a single polar flagella. Photo: CDC/Dr. William A. Clark Street seller serves contaminated corn drink from a single vessel. Photo: CDC Symptoms of Cholera: Symptoms of Cholera More than 90% of cases are of mild or moderate severity and are difficult to distinguish from other types of acute diarrhea. Fewer than 10% of ill people develop typical cholera with signs of moderate or severe dehydration. Transmission of Cholera: Transmission of Cholera Vibrio cholerae is often found in the aquatic environment and is part of the normal flora of brackish water and estuaries in tropical countries. Cholera is spread by water and food contaminated with the Vibrio cholerae bacterium Sudden large outbreaks are usually caused by a contaminated drinking water supply. In many parts of the world infected with cholera, the local waterways are the only source of water for drinking, washing, and bathing. Treatment of Cholera: Treatment of Cholera Case-fatality rates may be as high as 50% when cholera occurs in an unprepared community (i.e. no facilities for treatment or treatment is given too late). In contrast, a well-organized response can limit the case-fatality rate to less than 1%. Most cases of diarrhea can be treated adequately by giving a solution of oral rehydration salts. During an epidemic, 80-90% of cholera patients can be treated by oral rehydration alone, but patients who become severely dehydrated must be given intravenous fluids. In severe cases, antibiotics can reduce the volume and duration of diarrhea and reduce the presence of V. cholerae in the feces. Pfizer Cholera Cases in 2003: Cholera Cases in 2003 Cholera in Latin America: Cholera in Latin America Cholera struck Latin America in 1991 as part of the seventh cholera pandemic. Cholera had not been seen in Latin America for over a century. Within a year, cholera had spread to 11 countries and by the end of 1994 had spread throughout the continent. Initial epidemics January 1991 August 1991 February 1992 November 1994 Source : MMWR 4(11) (3/24/95) Tuberculosis: Tuberculosis Tuberculosis (TB) is a contagious disease caused by the bacterium Mycobacterium tuberculosis (MTB). Like the common cold, it is spread through the air when infectious people cough, sneeze, talk, or spit. Infectivity of MTB is high when MTB are propelled into the air. A person only needs to inhale a small number of the bacteria to be infected. Left untreated, each person with active TB will infect between 10 and 15 people. The Mantoux test is used to test whether a person has ever been exposed to TB. Tuberculin (a protein extracted from MTB) is injected into the arm. After a few days the arm is examined. If the test area is red, hard, and raised, it indicates previous exposure to TB, ensuring some form of immunity. Photo: CDC The Tuberculosis Epidemic: The Tuberculosis Epidemic A global epidemic is underway. It is growing rapidly in intensity, due mainly to: The breakdown in health services in some countries. The spread of HIV/AIDS. The emergence of multi-drug resistant TB (MDR-TB). In 1993, the World Health Organization (WHO) was so concerned about the epidemic that it took an unprecedented step and declared tuberculosis a global emergency. Pulmonary tuberculosis patient Photo: Surveillance & Epidemiology Branch, Centre for Health Protection, Hong Kong The Tuberculosis Epidemic: The Tuberculosis Epidemic By 1998, the WHO estimated that about one third of the world’s population were already infected with TB. They estimate that 8 million new cases are being added annually and that TB causes about 2 million deaths each year. It is anticipated that between 2000 and 2020: One billion people will be newly infected, 200 million people will get sick, and 35 million will die from TB. Chest X-ray of patient with severe pulmonary tuberculosis. The white spotting indicates tubercular lesions. Photo: Surveillance & Epidemiology Branch, Centre for Health Protection, Hong Kong Symptoms of Tuberculosis: Symptoms of Tuberculosis TB usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, and the spine. TB infected people may not get sick with the disease because the MTB may enter a dormant phase when the body’s immune response walls-off the bacteria in tiny, hard nodules known as tubercles. The bacteria may become active years later if the person’s immune system becomes weakened (due to some other illness, e.g. HIV/AIDS). Inset shows Mycobacterium stained pink Worldwide Cases of TB (2003): Worldwide Cases of TB (2003) NOTE : These figures reflect only the cases reported to the WHO. Many thousands (possibly millions) of cases are unreported each year. Drug Resistant TB: Drug Resistant TB With appropriate antibiotic therapy, TB can usually be cured. However, in recent years the number of drug-resistant cases of TB has increased dramatically. Drug resistance occurs when: Patients fail to take their full (6 to 12 months) course of medication necessary to destroy all M. tuberculosis present. Patients are treated with too few drugs or inadequate doses. One reason for this lack of compliance is that TB patients may feel better after only two to four weeks of treatment and stop taking their medication. The increase in the number of people with multi-drug resistant TB (MDR-TB) is particularly alarming. It is caused by M. tuberculosis strains resistant to two or more drugs. TB is of international concern Woman with TB medication Photo: CDC Photo: CDC MDR-TB in Russia: The tuberculosis (TB) epidemic in the Russian Federation has reached alarming proportions, particularly in the prison system. Russia has the highest incidence of MDR-TB in the world. This is a global problem because the Russian prisons act as an epidemiological pump releasing tens of thousands of active TB and MDR-TB cases and hundreds of thousands of infected individuals into the community each year. Young men enter prison and die even before their cases are tried in court, a process which may take up to 18 months. MDR-TB in Russia Black Death: Black Death Slide16: Historically there have been three recognizable plague pandemics. The first occurred during Roman times in the reign of Emperor Justinian (541 to 544 a.c.) and reoccurred several times in the next two centuries. It is believed to have killed upwards of 40 million people during that time and is believed to have been one of the causes of the fall of the Roman Empire. The disease was brought from the East via caravan routes, and then in the subsequent years spread throughout he empire with the movement of armies, traders and by sea to ports. The disease never really left Europe for 200 years. Slide17: The next great pandemic, known historically as the Black Death, begun around 1347 and was brought from the Crimea by Genoese sailors that fled from a Mongol siege of a city in that area. (Plague began in the Mongol army and was carried to the city by the Mongols themselves throwing dead bodies across the walls, an early method of biological warfare. The Mongols eventually lifted the siege of the city and left carrying the plague with them to the East.). The Genoese landed in the port city of Messina in Sicily. The disease raged north from there and covered all of Europe in three years (map). An estimated 1/3 to 1/2 of the European population of that time died of the disease. Institution of quarantine methods eventually stopped the epidemic. The disease also spread east to Asia Minor, the Near East, India and China. Chinese records of this time show that millions died in this pandemic. Slide18: The disease remained chronic in Europe from then to modern times with sporadic occurrences of epidemics. For example: two epidemics occurred in the city of Venice 1575-77 and 1630-31 causing the death of a third of the population each time. Epidemics occurred in Northern Spain in 1596-1602, 1648-52 and 1677-85 killing more than a million people (a possible cause of the decline of Spanish economic and political power). The Great Plague of London in 1665 killed half the population and was only stopped by the Great Fire of 1666. Epidemics continued to modern times when tha advent of immunization, the discovery of antibiotics made the disease trivial and easily curable. Slide19: From 1980 through 1994, 18,739 cases of plague and 1853 plague-related deaths were reported to the World Health Organization by 24 countries in Africa, the Americas, and Asia. Also from 1980 through 1994, 229 cases of plague were reported in the U.S., an average of about 15 per year, with 33 deaths. All but one (acquired in South America) was spread by flea bites from wild rodents in western states. The bacteria is endemic in wild rodent populations in the western US today. Plague is far from gone, especially since antibiotic resistant strains are beginning to appear. A 16 year old boy (from Madagascar), stricken with bubonic plague, was recently found to have a multi-drug resistant strain. This strain was found to be resistant to all first line antibiotics (streptomycin, gentamycin, tetracyclines and chloramphenicol).