Yellow fever.pptx

Yellow fever is a viral disease transmitted by the Aedes mosquito. India is free from yellow fever. Vaccination against yellow fever is available and is highly effective. A vaccination certificate is required to travel in a yellow fever free zone/country

1. Yellow Fever Dr Nitika Sharma Assistant Professor Community Medicine KCGMC, Karnal

2. Introduction Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. It a zoonotic disease caused by an arbovirus . The yellow fever virus is found in tropical and subtropical areas of Africa and South America .

3. The virus is spread to people by the bite of an infected Aedes mosquito. Illness ranges from a fever with aches and pains to severe liver disease with bleeding and yellowing of skin (jaundice).

4. Problem statement 47 countries in Africa and Latin America, with a combined population of more than 900 million, are at risk of yellow fever. In Africa, an estimated 508 million people live in 32 countries at risk.

5. Who is at risk Those who haven’t been vaccinated for yellow fever and who live in areas populated by infected mosquitoes are at risk. According to the  World Health Organization (WHO) , an estimated 200,000 people get the infection each year. Most cases occur in 32 countries in Africa, including Rwanda and Sierra Leone, and in 13 countries in Latin America, including: Bolivia Brazil Colombia Ecuador Peru

6. Colombia, Ecuador and Peru at greatest risk. The disease has never been reported in Asia , but the region is at risk because the conditions required for transmission are present there.

7. Epidemiological determinants

8. Agent factors (a) AGENT : The causative agent, Flavivirus fibricus (b) RESERVOIR OF INFECTION is mainly monkeys and forest mosquitoes . In urban areas, the reservoir is man (subclinical and clinical cases) besides Aedes aegypti mosquitoes.

9. (c) PERIOD OF COMMUNICABILITY : ( i ) MAN : Blood of patients is infective during the first 3 to 4 days of illness. (ii) MOSQUITOES : After an "extrinsic incubation period" of 8 to 12 days, the mosquito becomes infective.

10. Host factors AGE AND SEX : All ages and both OCCUPATION : Persons are in contact with forests (wood cutters, hunters) where yellow fever is endemic. IMMUNITY : One attack of yellow fever gives lifelong immunity.

11. Environmental factors (a) CLIMATE : A temperature of 24 deg. C or over is required for the multiplication of the virus in the mosquito. It should be accompanied by a relative humidity of over 60 per cent for the mosquitoes to live long enough to convey the disease.

12. (b) SOCIAL FACTORS : In Africa, urbanization Also encroaching on areas that were previously sparsely populated Bringing man closer to the jungle- cycles of yellow fever. Global travel and the greater speed with which travelers are transported from endemic areas to receptive areas, also a cause for concern.

13. Transmission Yellow fever virus is an RNA virus that belongs to the genus  Flavivirus . It is related to West Nile, St. Louis encephalitis and Japanese encephalitis viruses. Yellow fever virus is transmitted to people primarily through the bite of infected  Aedes  or  Haemagogus   speci -es mosquitoes.

14. Mosquitoes acquire the virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human). People infected with yellow fever virus are infectious to mosquitoes (referred to as being “viremic”) shortly before the onset of fever and up to 5 days after onset.

15. Modes of transmission Three known cycles of transmission : The jungle-or Sylvatic yellow fever. Intermediate yellow fever. Urban cycles yellow fever.

16. Sylvatic (or jungle) yellow fever: In tropical rainforests-It occurs in monkeys that are infected by wild mosquitoes. The infected monkeys then pass the virus to other mosquitoes that feed on them. The infected mosquitoes bite humans enter ing the forest, resulting in occasional cases of yellow fever. The majority of infections occur in young men working in the forest (e.g. for logging).

17. Intermediate yellow fever. In humid or semi-humid parts of Africa, Semi-domestic mosquitoes (that breed in the wild and around households) infect both monkeys and humans. Increased contact between people and infected mosquitoes leads to transmission.

18. Contd...... This is the most common type of outbreak in Africa. An outbreak can become a more severe epidemic if the infection is carried into an area populated with both domestic mosquitoes and unvaccinated people.

19. Urban yellow fever. Large epidemics occur when infected people introduce the virus into densely populated areas with a high number of non-immune people and Aedes mosquitoes. Infected mosquitoes transmit the virus from person to person.

20. Symptom Most people will not have symptoms. Some people will develop yellow fever illness with initial symptoms including: Sudden onset of fever Chills Severe headache Back pain General body aches

21. Nausea Vomiting Fatigue (feeling tired) Weakness Most people with the initial symptoms improve within one week. For some people who recover, weakness and fatigue (feeling tired) might last several months.

22. A few people will develop a more severe form of the disease. For 1 out of 7 people who have the initial symptoms, there will be a brief remission (a time when patient feels better) that may last only a few hours or for a day, followed by a more severe form of the disease.

23. Toxic phase During the toxic phase, acute signs and symptoms return and more-severe and life-threatening ones also appear. These can include: Yellowing of your skin and the whites of your eyes (jaundice) Abdominal pain and vomiting, sometimes blood in vomitus Decreased urination Bleeding from nose, mouth and eyes Bradycardia Liver and kidney failure Brain dysfunction, including delirium, seizures and coma Among those who develop severe disease, 30-60% die

24. Risk factors Travel to an area where mosquitoes continue to carry the yellow fever virus including sub-Saharan Africa and tropical South America. Even if there aren't current reports of infected humans in these areas, it doesn't mean being risk-free. It is possible that local populations have been vaccinated and are protected from the disease, or that cases of yellow fever just haven't been detected and officially reported. Anyone can be infected with the yellow fever virus, but older adults are at greater risk of getting seriously ill.

25. Complications Yellow fever results in death for 30 % to 60% of those who develop severe disease. Complications during the toxic phase of a yellow fever infection include kidney and liver failure, jaundice, delirium, and coma. People who survive the infection recover gradually over a period of several weeks to months, usually without significant organ damage. Other complications include secondary bacterial infections, such as pneumonia or blood infections.

26. Diagnosis Yellow fever is difficult to diagnose, especially during the early stages Polymerase chain reaction (PCR) testing in blood and urine ELISA

27. Treatment No specific treatment Only supportive care-dehydration and fever. Associated bacterial infections can be treated with antibiotics. Supportive care may improve outcomes for seriously ill patients

28. Control of yellow fever

29. Jungle yellow fever Jungle yellow fever continues to be an uncontrollable disease. Vaccination of humans with 17D vaccine is the only control measure.

30. Urban yellow fever (1) VACCINATION: Rapid immunization of the population at risk is the most effective control strategy for yellow fever. For international use, the approved vaccine is 17D vaccine It is a live attenuated vaccine prepared from a non- virulent strain (17D strain), which is grown in chick embryo and subsequently freeze-dried.

31. The vaccine is administered subcutaneously at the insertion of deltoid in a single dose of 0.5 ml irrespective of age. Immunity begins to appear on the 7th day and lasts possibly for life

32. (3) SURVEILLANCE : A programme of surveillance (clinical, serological, histopathological and entomological) should be instituted in countries where the disease is endemic, for the early detection of the presence of the virus in human populations or in animals that may contribute to its dissemination.

33. For the surveillance of Aedes mosquitoes, the WHO uses an index known as Aedes aegypti index. This is a house index and is defined as ·'the percentage of houses and their premises, in a limited well-defined area, showing actual breeding of Aedes aegypti larvae" . This index should not be more than 1 per cent in towns and seaports in endemic areas to ensure freedom from yellow fever

34. International measures India is a yellow fever "receptive" area, that is, "an area in which yellow fever does not exist, but where conditions would permit its development if introduced". The population of India is unvaccinated and susceptible to yellow fever. The vector, Aedes aegypti is found in abundance. The climatic conditions are favourable in most parts of India for its transmission.

35. The missing link in the chain of transmission is the virus of yellow fever which does not seem to occur in India.

36. The virus of yellow fever could get imported into India in two ways: ( i ) through infected travellers (clinical and subclinical cases}, (ii} through infected mosquitoes. Measures designed to restrict the spread of yellow fever are specified in the "International Health Regulations" of WHO

37. Travellers from endemic zones of yellow fever must possess a valid international certificate of vaccination against yellow fever. The aircraft and ships arriving from endemic areas are subjected to aerosol spraying with prescribed insecticides on arrival for destruction of insect vectors.

38. Airports and seaports are kept free from the breeding of insect vectors over an area extending at least 400 metres around their perimeters. The " aedes aegypti index" is kept below 1.

39. Get vaccinated With 17 D vaccine

40. International certificate of vaccination India and most other countries require a valid certificate of vaccination against yellow fever from travellers coming from infected areas. A few countries (including India) require this even if the traveller has been in transit.

41. It rests with each country to decide whether a certificate of vaccination against yellow fever shall be required for infants under one year of age, after weighing the risk of importation of yellow fever by unvaccinated infants against the risk to the infant arising from vaccination. In this regard, India requires vaccination of infants (> 9 months of age) too.

42. The validity of the certificate begins 10 days after the date of vaccination. For the purpose of international travel, the vaccination must be given at an officially designated centre , and the certificate must be validated with the official stamp of the Ministry of Health, Government of India.

43. The certificate is valid only if it conforms with the model prescribed under the International Health Regulations. On the other hand, for their own protection, travellers who enter endemic areas should receive vaccination against yellow fever

44. Nearby centres for yellow fever vaccination are at Delhi

45. The Elimination Yellow Fever Epidemic (EYE) Strategy- 2017 to 2026

46. urban outbreaks in 2016 demonstrated that despite the advances in immunization activities, challenges remain in ending yellow fever epidemics. The EYE Strategy objectives address these challenges. The strategy aims at building a global coalition to tackle the increased risk of yellow fever epidemics in a coordinated manner and to demonstrate new ways of managing re-emerging infectious diseases. Activities supported through the EYE Strategy work by implementing large-scale interventions to prevent epidemics.

47. The EYE Strategy was developed by WHO, UNICEF and GAVI, in response to increased threat of yellow fever urban outbreaks with international spread. It is guided by three strategic objectives ·: 1. Protect at-risk populations 2. Prevent international spread of yellow fever; 3. Contain outbreaks rapidly.

48. Protect at risk populations Immunization  is considered to be the most important and effective measure against yellow fever. A single dose of yellow fever vaccine is sufficient to provide life-long immunity and protection against the disease. The EYE strategy aims at ensuring universal access to yellow fever immunization so that each and every person in yellow fever at-risk countries is protected against the disease. Risk assessment is done to equitably implement preventive interventions- preventive mass vaccination campaigns and introduction of yellow fever vaccine into routine immunization.   EYE strategy engages with vaccine providers and global health partners to increase vaccine production, making it an affordable endeavor.

49. Prevent international spread EYE Strategy aims to protect high-risk workers (e.g. persons involved in extractive industries at risk for sylvatic exposures), strengthen application of International Health Regulations (IHR 2005) (e.g. increase compliance with vaccination requirement verification at points of entry), and support development of resilient urban centres (e.g. development of readiness plans to reduce risk of large-scale yellow fever outbreak and increase vector control measures).

50. Contain outbreaks rapidly   Outbreaks are unusual events that require additional resources and partner support. Rapid containment of an outbreak is essential to prevent amplification into devastating epidemics. It is dependent on early detection and confirmation; emergency vaccine stockpiles and rapid response. The EYE Strategy is working to improve surveillance and diagnostics to facilitate early detection of outbreaks and rapid response to outbreaks and to assure global stockpile is maintained with a stock of 6 million doses at all times.

51. These objectives are underpinned by five competencies of success: 1. Affordable vaccines and sustained vaccine market; 2. Strong political commitment at global, regional and country levels ; 3. High-level governance with long-term partnerships; 4. Synergies with other health programmes and sectors; 5. Research and development for better tools and practices

52. THANK YOU