Download Study of Disease Occurrence and Transmission | MIC 205A and more Study notes Microbiology in PDF only on Docsity! 1 Epidemiology Study of Disease Occurrence and Transmission Emerging Infectious Disease • Mutation of organism to new serovar (antigenic type) • Migration of humans and animals into new environments • Travel • War and natural disasters • Decline in vaccination rates • Climatic changes Microbe of the Day • Vibrio cholerae • Gram negative curved rod • Toxin alters sodium pump in intestinal cells fluid loss Cholera 1800s Cholera: the Disease • Entry: oral • Colonization: small intestine • Symptoms: nausea, diarrhea, muscle cramps, shock Infant with Cholera 2 First Cholera Pandemic • Why does an epidemic end? Second Cholera Pandemic Cholera New York 1830s John Snow and the Pump Handle John Snow and cholera in 1854 London http://www.ph.ucla.e du/epi/snow.html John Snow • John Snow is credited by many with developing the modern field of epidemiology 5 Cholera in the 1990s • Epidemic in Peru beginning 1991 • From 1991-1994 –Cases 1,041,422 –Deaths 9,642 (0.9%) • Originated at coast, spread inland World Cholera 2000-01 Why Has Cholera Re-emerged? • Deteriorating sanitary facilities as larger population moves into shanty towns • Trujullo, Peru – fear of cancer from chlorination so water untreated • Use of wastewater on crops • Africa – civil wars and drought caused migrations into camps How Has Cholera Re-emerged? • Simultaneous appearance along whole coast of Peru • Traveled in ship ballast? • Traveled in plankton from Asia? • Always present in local zooplankton (copepods) but dormant until triggered by ??? Copepod Carrying Vibrio cholerae 6 Cholera and El Niño • Periodic warming of water near coast of Central and South America • Large plankton blooms, especially in coastal waters with nutrients from sewage runoff Cholera and El Niño • Cholera in Bangladesh also seen to fluctuate with El Niño, but with 11 month lag • Rita Colwell and multinational group studying link between climate and cholera • Satellite and surface data used to show cholera incidence is related to sea surface temperature Cholera from Space Cholera and Sea Surface Temperature Cholera in the 1990s • Cholera O139 emerges in Asia • Different O (coat) antigen, 99% genetic identity • O antigen is how human immune system recognizes and protects against V. cholerae • More people susceptible 7 Cholera Antibiotic Resistance • Cholera is becoming resistant to several antibiotics
