Measles a Plague of Populations

Measles, a Plague of Populations Virus Ecologic niches (– so far in MIC438) Animal Animal Human SARS, Nipah, Rabies, Bird Flu, BSE Insect Animal Animal Bird Bird Insect Human YF, Dengue Insect Insect Human WNV Measles, a Plague of Populations Human only Human Human Measles Smallpox (eradicated) Polio (eradication efforts underway) HIV Hepatitis A, B, C Human Human Measles and Smallpox are explosive diseases (like TB) because of efficient respiratory spread. Measles is THE most communicable infectious disease! Measles, a Plague of Populations If Measles infects humans only, And humans are immune after infection   Then measles would die out in closed small populations! This is exactly what happens. Measles spread depends on new susceptible host - people Influx of people, or  New generation: enough children!  Measles, a Plague of Populations Measles in small island populations As the island size decreases, the percent of months in a year with measles cases decreases As the distance between susceptibles decreases, the duration of the epidemic decreases The Burden of Infectious and Parasitic Disease   World Wide IPDs  25-30 % of all deaths annually = 15-20 million Pneumonia TB HIV Diarrhea Malaria Measles Hepatitis B 14% 10% 10% 10% 8% 6% 3% 60% are infants Leading IPD killers (Percent of deaths)        80% are infants 95% are infants  97% in developing / underdeveloped countries The Burden of Infectious and Parasitic Disease  The underdeveloped world is impoverished, malnourished, and  Infected!  Poor water, crowding, no health services, few vaccines, a young population  Multiply infected! The Burden of Infectious and Parasitic Disease Disease Measles World vs USA ~100 cases v. rare death Pneumonia Diarrhea 40-45 million annually 150-200 / 1000 die most < 1 year old 4 million 82/100 die 3 million 56/100 die 50,000 cases << 1/100 die 100,000 cases << 1/100 die Measles in Developing Countries CDC Data … Control of Measles in USA 1989-91: Spike of cases in US ~About 25 in the peak Completion of vaccination campaigns Vaccine became available in 1962 Control of Measles in USA  Deaths controlled by 1950   Quarantine of households with cases Public health measures and cooperation Effective vaccination Compliance  Cases controlled by 1968    Minor outbreaks still occur in Unvaccinated Control of Measles in USA  Minor outbreaks in USA    Religious groups against vaccinaton Militant resistance to vaccination Not vaccinated because of social poverty  Where does the virus come from in the USA? Measles Pathogenic Pathway ?  Respiratory droplet  throat  local lymph nodes  virus replicates in epithelial cells and lymphocytes (transient immunosuppression)  viremia, spread of virus throughout the body, to other lymphoid organs like the spleen  return of the virus to epithelial surfaces  skin – RASH  brain – Encephalitis (rarely)  lungs – Pneumonia (in AIDS)  Recovery, lifelong immunity Measles Pathogenic Pathway Diagram 1. Virus is shed from respiratory tract just as signs of disease start and lasts for 7+ days 2. Transmission takes place 7+ days before illness Measles Outbreak in a Community with Very Low Vaccine Coverage, the Netherlands Epidemic curve Attack rate, by date of birth: Children 1-7 AFECTED MOST Measles Attack Rates Primary Cases, Households Only those with no vaccine or unknown status came down with Measles The attack rate for susceptibles was 86% Where does the virus come from in the USA? Spread of Measles in the USA due to inadequate vaccination - No vaccination or less than the 3 doses Result: Mandate vaccination - College admissions - Community clinics Where does the virus come from in the USA? Measles virus can be typed using sequence data from case isolates 8 clades, world wide What is REALLY going on with Measles? What is REALLY going on with Measles? Importation Scenario Case: Measles: Mexico from the USA?     A person had an onset of measles on 13 April in Mexico. The patient visited Texas on April 10th. A question arose about the possible exposure of the person to measles in Texas. But during this year Texas has had only one case of measles in an adoptee exposed in China with an onset on 14 Feb. They did not have any cases of measles in the previous year, and in the year before that Texas had 7 cases of which 6 were directly related to international travel. The incubation period for measles from exposure to rash onset averages 14 days (range 7-18 days). The incubation period from exposure to prodromal illness is 10-12 days with the prodrome usually lasting 2-4 days. Is it possible that this person contracted measles in Texas and carried it to Mexico?