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

9. ◦ 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.

10. EPIDEMIOLOGICA
L
DETERMINANTS

11. 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.

12. (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.

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

14. 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.

15. (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.

16. 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.

17. ◦ 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.

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

19. ◦ 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 entering 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).

20. ◦ 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.

21. 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.

22. ◦ 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.

24. 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

25. ◦ 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.

26. • 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.

27. 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

28. 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.

29. 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.

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

31. 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

33. CONTROL OF
YELLOW FEVER

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

35. 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.

36. ◦ 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

37. (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.

38. 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

39. 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.

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

41. ◦ 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

42. ◦ 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.

43. ◦ 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.

44. Get vaccinated
With 17 D
vaccine

45. 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.

46. ◦ 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.

47. ◦ 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.

48. ◦ 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

49. Nearby centres for yellow fever vaccination are
at Delhi

51. THE ELIMINATION YELLOW
FEVER EPIDEMIC (EYE)
STRATEGY- 2017 TO 2026

52. • 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.

53. ◦ 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.

54. 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.

55. 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).

56. 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.

57. ◦ 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