EPI 390Exam # 2 Study Guide Lectures: 10 - 15Lecture 10 - Smallpox:Clinical course of the disease- Incubation period is 7-17 days- First 7-17 days feel slightly ill. 2-3 days of spike in illness and then lesions start. Lesions can last a couple weeks, and cover everything (unlike chicken pox which are more mild)- Day 5 of symptoms (not incubation) fever starts, lesions everywhereModes of transmissionSmallpox is a human only disease with no animal vectors; it is highly contagious.Person to person transmission occurs via respiratory route (inhalation of droplets from coughing/talking, more rarely via aerosol)Direct contact is less common (w/ infected fluids or items)No transmission from animal reservoir (only spread from another smallpox case)The Prodrome phase (fever, no rash) is less contagiousMost contagious with rash, remain contagious until last scab is goneBasic biology of the diseaseSmallpox virus is a double-stranded DNA virus of the orthopox family. It is the largest known virus.Distinguishing feature of smallpox vs. Chicken pox: smallpox is found in the periphery, limbs, andface. Chicken pox tends to stay concentrated in chestTypes of smallpox- Convergence of lesions (combining of 2 lesions) is a bad prognosis. Confluent smallpox has very high mortality - 70% mortality in sheet mortality – when almost all lesions are confluent. - Hemorrhagic smallpox (bleeding to lesions) is almost 100% fatal- Variola Minor – a mild strain of smallpoxVariolation/Inoculation/Insufflation- Variolation – People realized that if you had smallpox once, you wouldn’t get infected with it again. They would use various parts of smallpox material from the infected (i.e. ground up scabs, or puss, etc.) and would administer in various ways- Insufflation – inhaling particles of smallpox. i.e. in China, they ground scabs into powder and inhaled it.- Inoculation – Placing a part of the disease in the body so it will grow and reproduce. i.e. India applied material to skin. Turkey dipped string into pus then would cut open arm and slide string through cut. This created “mild” case; 1-2% fatality still. History of VaccinationLate 18th century: vaccination introducedEdward Jenner – noticed that milkmaids didn’t get smallpox (milkmaid complexion was prized b/c never had smallpox scarring). They got cowpox, a mild infection of hands gotten from cow udders. The vaccination process: would create one lesion. Take a little from lesion to create lesion on next person. Would vaccinate one person to another (young person or child). Got vaccination toUS by spreading lesion one person at a time; by the time they reached the US from England, thelast person had been vaccinated and still had a lesion that could be used in US.Last US case was 1948, 1966 risk of dying from vaccine was higher than risk of generating disease so stopped compulsory vaccination (only had to get it if traveling to pandemic place)Islands are easiest place to eradicate diseaseImportant dates, people, and placesLady Mary Wortley Montague - tested Turkish method in London/England. Tested it on convicted murderers set to be executed. They could either be executed or be inoculated. If they chose inoculation and survived, they’d be pardoned. All were pardoned.Edward Jenner, late 18th century – developed vaccinations for smallpox from Cowpox.1948 – The last case of smallpox in the USHenderson and Bedson led the 13-year Smallpox Eradication campaign1967 – many countries eradicated. Some small cases of importations. Still endemics in more developing countries.Mass vaccination campaignFirst stage focused on mass vaccination.Challenges: Haj in mecca (pilgrimage destination)Refugees i.e. from Pakistan-Bangladesh warPort outbreak – when the people in the area went home, caused widespread diffusion ofmini outbreaksTough travel conditions to reach everyoneGetting the public to agree to mass vaccinationFor final stages of eradication: isolation zones (aka ring vaccination).Effect of vaccination on smallpox mortality in England/SwedenWhen vaccination was implemented, and when it was made mandatory, there were sharp decreases in the number of smallpox cases and deaths from smallpox. There were occasional spikes in infections, due to people avoiding vaccination, but overall the trend was one of decline.Endemics in smallpox ended in 1895 in Sweden, and 1934 in England.Importance of cowpox/monkeypoxCowpox is transmitted from cow’s udders to humans. It is a non-lethal infection that can be used to prevent smallpox infectionMonkey pox – found in monkeys in 1958, can cause human outbreaks. The disease does cause occasional deaths, mostly in children. Also has rodent host, which creates the possibility of an animal reservoir spreading the disease. Usually, monkey pox is isolated in Congo but had outbreak of monkey pox in US about 7 years ago. Transmitted in prairie dogs in US; pet prairie dogs had been in contact with imported African rodents.Cyclicity of outbreaksFluxes in immunity due to birth of new babies that aren’t immuneResults of mandatory smallpox vaccinationSharp declines in smallpox cases were noticed. Any spikes in the number of cases were due to incomplete vaccination leaving part of the population exposed.What is vaccinia necrosum?A dangerous reaction to vaccination that occurs in immune-suppressed individuals. It results in tissue death at the site of the vaccination.You should know trends related to smallpox in the US in the 20th century:When in 20th century did cases reach a peak?1920About how many deaths?110,000What are the deaths trends (not the exact #s) by decade?An increase from 1900 to 1920 (a sharp increase between 1910 and 1920). From 1920 to 1950, though, the number of deaths greatly decrease until there were 0 cases (and therefor, 0 deaths) in 1950.When were there no more deaths?No more deaths in 1950, excluding the few exceptions (i.e. the engineer from Pakistan and Janet Parker)Problem of cross-national importation of the virusImported outbreaks – travellers could be infected in countries where the virus hadn’t been eradicated and then they would bring the disease back home and infect othersi.e. the Engineer who went to Pakistan: vent ducts spread his disease throughout hospital. Shows how communicable smallpox was (one visitor infected after only 15 min in hospital and went nowhere near engineer’s room)Keys to control of outbreaks- Mass vaccination- Educating the public to