Dr.I.Selvaraj,I.R.M.SB.SC.,M.B.B.S.,(M.D Community medicine).,D.P.H.,D.I.H.,P.G.C.H&FW(NIHFW,New delhi)

Sr.D.M.O(ON STUDY LEAVE)

INDIAN RAILWAYS MEDICAL SERVICE

In 1881, Carlos Juan Finlay, a physician in Havana, first proposed that yellow fever was a mosquito-borne illness, which subsequently was proven by Walter Reed and colleagues.

U.S. Army doctor Discovered the Cause of Yellow Fever August 27, 1900

Research and Walter Reed

Walter Reed, M.D., (1851-1902) was an American Army surgeon who led the team which proved the theory first set forth in 1881 by the Cuban doctor and scientist Dr. Carlos Finlay that yellow fever is transmitted by mosquitoes rather than direct contact. The risky but fruitful research work was done with human volunteers, including some of the medical personnel such as Clara Maass and surgeon Jesse W. Lazear Walter Reed Medal winner who allowed themselves to be deliberately infected and died of the virus. All this lead to the elimination of Yellow Fever from Cuba and allowed the final construction of the Panama Canal.

Clara Maass

On August 14, 1901, Maass allowed herself to be bitten by infected mosquitoes for the seventh time. Maass once again became ill with yellow fever on August 18 and died on August 24. Her death roused public sentiment and put an end to yellow fever experiments on humans.

•Thirty-three countries, with a combined population of 508 million, are at risk in Africa. These lie within a band from 15°N to 10°S of the equator.

• In the Americas, yellow fever is endemic in nine South American countries and in several Caribbean islands. Bolivia, Brazil, Colombia, Ecuador and Peru are considered at greatest risk.

•There are 200,000 estimated cases of yellow fever (with 30,000 deaths) per year.

Countries regarded as yellow fever infectedAfrica: 

Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Democratic Republic of Congo (Zaire), Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast (Cote D'Ivoire), Kenya, Liberia, Mali, Niger, Nigeria, Rwanda, Sao Tome and Principe, Senegal, Sierra Leone, Somalia, Sudan (South of 15° N), Togo, Uganda, Tanzania, Zambia.

America: 

Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Trinidad and Tobago, Venezuela, Panama.

•As of 6 December 2005, the Federal Ministry of Health,SUDAN reported to WHO a total of 565 cases, including 143 deaths, with a case fatality rate of 25.3%.

•As of 19 December2005, the Ministry of Health, Guinea has reported a total of 114 suspected cases of yellow fever with 26 deaths, Twenty-three of these cases have been laboratory confirmed.

There are no reported cases of yellow fever in Asia. It is suspected that the high incidence of dengue fever helps confer protection against yellow fever, and that the Asian mosquito strains are not as competent as vectors of the disease.

AGENT

• Genus :Flavivirus fibricus,

Group B Arbovirus

Family : Toga virus

• The yellow fever virus is 35-40 nm in

• size. It consists of a single strand of RNA virus

The photomicrograph shows multiple virions of the yellow fever virus at a magnification of 234,000x

Aedes mosquitoes, including A. aegypti, A. africanus, A. simpsoni, A. furcifer, B. luteocephalus, and A. albopictus (Asian tiger mosquito).  Urban yellow fever is transmitted by the Aedes aegypti

mosquito.    Jungle, or sylvatic, yellow fever is transmitted by Haemagogus and other mosquitoes (such as Masoni africana) of the forest canopy (tree-hole breeding mosquitoes).  

VECTORS

• Reservoir: Monkey, Human, Mosquito

• Incubation period: Intrinsic IP:3to 6 Days

Extrinsic IP: 1to 2 weeks

.Period of communicability: First 4 days of illness

Mode of Transmission : 1.Sylvan cycle

2. Urban cycle

Race: No known racial predilection exists.

Sex: Both sexes are infected equally

Age: All ages are suceptible to yellow fever.

Jungle yellow fever primarily affects nonimmunized adults who work as foresters,wood cutters & hunters in endemic areas and persons residing on the edge of the jungle.

Infants born of immune mothers have antibodies up to 6 months of life

ENVIRONMENTAL FACTORS

• TROPICAL CLIMATE

• HUMIDITY (60%)

• TEMPERATURE ( 24ºC)

• SOCIAL FACTORS : URBANISATION , TRAVEL &EXCESSIVE RAINS

• The natural host for the yellow fever virus in forest areas is non-human primates (usually monkeys and chimpanzees).

• The vectors of yellow fever in forest areas in Africa are Aedes africanus . In South America, the primary vector is the Haemagogus species.

• In urban areas of both Africa and South America, the vector is Aedes aegypti.

The natural yellow-fever cycle is mosquito-monkey-mosquito.

 The shift from jungle yellow fever to urban yellow fever is thought to be the result of humans entering the sylvan setting and becoming part of the yellow-fever cycle:

 Initially, wood cutters and other forest workers were bitten by forest-canopy mosquitoes carrying the yellow-fever virus.  The humans then returned to the urban settings.  

Clinical features of yellow fever

Yellow fever presents with a variety of clinical signs and outcomes ranging from mild to severe and fatal cases. Yellow fever in human beings has the following characteristics:

· An acute phase lasting for four to five days and presenting with:

- a sudden onset of fever

- headache or backache

- muscle pain

- nausea

- vomiting

- red eyes (infected conjunctiva).

The diagnosis can be strongly suspected when Faget's sign is present. Faget's sign: The simultaneous occurrence of a high fever with a slowed heart rate.

This phase of yellow fever can be confused with other diseases that also present with fever, headache, nausea and vomiting because jaundice may not be present in less severe (or mild) cases of yellow fever. The less severe cases are often non-fatal.

· A temporary period of remission follows the acute phase in 5% to 20% of cases. The period of remission lasts for up to 24 hours.

A toxic phase can follow the period of remission and presents with:

- jaundice

- dark urine

- reduced amounts of urine production

- bleeding from the gums, nose or in the stool

- vomiting blood

- hiccups

- diarrhoea

- slow pulse in relation to fever

No specific treatment is available for yellow fever. In the toxic phase, supportive treatment includes therapies for treating dehydration and fever. In severe cases, death can occur between the seventh and tenth days after onset of the first symptoms.

http://www.cmaj.ca/content/vol170/issue13/images/large/19tt2.jpeg

CONTROL OF YELLOW FEVER

Theiler won Nobel Prize in 1951 for his accomplishments

YELLOW FEVER VACCINE

• The virus first isolated in 1927 by inoculating rhesus monkeys with the blood of an African patient (Asibi).

• Edward Hindle developed inactivated vaccine 1928.Theilar and Smith developed 17D vaccine from the Asibi strain in cell cultures from embryonated chicken eggs.

• It is a safe & effective vaccine.

• Yellow Fever Vaccine, Live (17D Strain Live, Freeze Dried).Each 0,5 mL contains Yellow Fever Virus 104.1 pfu.

• Vaccine must be maintained continuously at temperatures between 5 and -30°C

• The vial of diluent should not be allowed to freeze.

• The reconstituted vaccine must be kept cool and used within 60 minutes following reconstitution.

• The product appears slightly opalescent and light orange in color after reconstitution.

• Vials of 5 doses with vials of diluent.

• Reconstitute the vaccine using only the diluent supplied (Sodium Chloride Injection).

• Slowly inject the diluent into the vial containing the vaccine, let stand for one or two minutes and then carefully swirl mixture until a uniform suspension is achieved. Avoid vigorous shaking as this tends to cause foaming of the suspension.

• Administer the vaccine subcutaneously.

The yellow fever vaccine has a long record of safety, but clinicians should be aware of two severe complications from the vaccine.

1. Yellow fever-associated neurotropic disease (previously known as post vaccine encephalitis), occurs 7–21 days after vaccination. Of the 1/8 000 000 people who contract this disease, full recovery is typical.

2. Yellow fever-associated viscerotropic disease occurs 2–5 days after vaccination. It is characterized by fever, myalgia, arthralgia, increased liver enzymes and bilirubin, lymphopenia, thrombocytopenia, disseminated intravascular coagulation, hypotension, oliguria and rhabdomyolysis. There have been 13 cases reported out of over 100 million doses administered worldwide.

Persons exempted from production of vaccination

1.Infants below the age of six months.

2. Crew and passengers of an aircraft transiting through an airport located in yellow fever infected area provided the Health Officer is satisfied that such persons remained within the airport premises during the period of stay.

•The validity period of international certificate of vaccination or re-vaccination against yellow fever is 10 years, beginning 10 days after vaccination.

REFERENCE CENTRES INDIA

• 1. National Institute of Virology, Pune

• 2. Central Research Institute, Kasauli

Aedes aegypti index

It is a house index.It is defined as “the percentage of houses and their premises showing actual breeding of Aedes aegypti larvae. This index should not be more than 1% in airports and seaports in endemic areas at least 400 meters around their perimeters to ensure freedom from yellow fever

MosquiTRAP. is a novel, simple, easy, low cost, and efficient trap especially developed to catch Aedes mosquitoes. MosquiTRAP. allows the identification of the mosquito species in the field, thus saving time and avoiding laboratory routine such as counting eggs and larval identification. Trapped mosquitoes can also be used for virus diagnosis. New entomological indices are

(a) the Positive MosquiTRAP Index

(PMI), the percentage of positive traps,

and (b) the Adult Density Index for A. aegypti and for A. albopictus. Field data can be collected using hand-held PDAs and then loaded directly into a Geographical Information System (GIS), for an efficient determination of local entomological indices.

YELLOW FEVER RECEPTIVE AREA

• An area in which yellow fever does not exist, but where conditions would permit its development if introduced

• The population of India is unvaccinated

• The vector Aedes aegypti is found in abundance

• The climactic conditions are favourable for its transmission

• The common monkey of India is more susceptible for yellow fever

• The missing link is in the chain of transmission is the virus of yellow fever

INTERNATIONAL MEASURES

• A valid international certificate of vaccination

• Aerosol spraying of prescribed insecticides on the arrival of aircrafts and ships from endemic areas

• Airports and seaports are kept free from the breeding of insect vectors at least 400 meters around their perimeters

• Clinical surveillance, entomological surveillance, epidemiological surveillance

• A) For entry into India:- Any person, Foreigner or Indian, (excluding infants below six months) arriving by air or sea without a vaccination certificate of yellow fever will be kept in quarantine isolation for a period up to 6 days if:

• He arrives in India within 6 days of departure from an infected area.

• Has come on a ship which has started from or transited at any port in a yellow fever affected country within 30 days of its arrival in India provided such ship has not been disinfected in accordance with the procedure laid down by WHO.

• (B) For leaving India:There is no health check requirement by Indian Government on passengers leaving India.

• The Government of Guyana requires that all persons including diplomats traveling to that country from India to possess valid yellow fever and cholera inoculation certificates before they leave India.

GUIDELINES FOR YELLOW FEVER SURVEILLANCE

• Make sure that personnel at health facilities in the district know how to identify suspected cases of yellow fever.

• Make sure that health facilities use a standard case definition to report suspected cases of yellow fever.

• Assist health facilities with investigation of suspected cases.

• Collect samples for diagnostic testing and laboratory confirmation. If necessary, transport samples to a drop-off point or specified laboratory.

• Notify the national level about the suspected case. Alert other health facilities in nearby areas about the potential for additional cases.

• Receive and report laboratory results about confirmed cases.

• Coordinate the response to the confirmed case with a district emergency response committee.

• Carry out intensified surveillance activities to identify additional cases in areas where the patient lived, worked or travelled. Collect diagnostic specimens from any new suspected cases.

• Monitor and supervise routine disease surveillance activities. Analyse data for trends suggesting a yellow fever outbreak. Report data from routine activities to the national level on time.

• Assist and support health facilities with the integration of yellow fever vaccine into the routine childhood immunization schedule. Make sure vaccine and immunization supplies are available for routine yellow fever activities.

• Ref : Monitoring the mosquito Aedes aegypti: A novel surveillance method and newentomological indices using the gravid trap MosquiTRAP. and a synthetic oviposition attractant (AtrAedes.)

• Ref: Aedes aegypti survey of Chennai* Port/Airport, India

• PREVENTIVE &SOCIAL MEDICINE 18th edition

• TEXT OF COMMUNITY MEDICINE –T. BHASKAR RAO

• Manson’s tropical disease – 21st edition

• http://www.who.int/vaccines-documents/DocsPDF/www9834.pdf

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