Yellow fever

Yellow fever is a viral hemorrhagic fever caused by Viscerophilus tropicus, an enveloped single stranded RNA arbovirus belonging to the Flavivirus genus.
1st viral disease to be discovered
Not present in india and Russia
IP: 2-6 days
Quarantine period: 6 days
Reservoir: Monkeys, Man, Aedes

1. Yellow fever

2. Outline: Introduction
Epidemiology
Transmission Pathogenesis Clinical manifestations Diagnosis Treatment Prevention Syndromes DDx

3. Introduction: Yellow fever is a viral hemorrhagic fever caused by Viscerophilus tropicus, an enveloped single stranded RNA arbovirus belonging to the Flavivirus genus. 1 st viral disease to be discovered Not present in india and Russia
IP: 2-6 days
Quarantine period: 6 days
Reservoir: Monkeys, Man, Aedes

4. Epidemiology: As a result of disease control programs in many countries, yellow fever is now endemic only in parts of sub-Saharan Africa and South America.
It is estimated that there are about 200,000 cases a year resulting in more than 30,000 deaths annually

5. Transmission: Yellow fever is transmitted by female mosquito vectors. In Africa, the Aedes species, particularly A. Eagypti is involved while in South America, the Haemogogus species is the dominant vector. Aside from human hosts, yellow fever also has a natural reservoir in primates.

6. Pathogenesis After transmission from a mosquito, the viruses replicate in the lymph nodes and infect dendritic cells in particular. From there, they reach the liver and infect hepatocytes (probably indirectly via Kupffer cells), which leads to eosinophilic degradation of these cells and to the release of cytokines. Apoptotic masses known as Councilman bodies appear in the cytoplasm of hepatocytes.
Fatality may occur when cytokine storm, shock, and multiple organ failure follow.

7. Incubation: 3-6 Days Period of Infection Period of Remission Period of Intoxication

8. Clinical Manifestations (3 stages) The first stage , or period of infection, is one of severe, non-specific signs of systemic illness corresponding with viremia associated with fevers, malaise, headache, photophobia, nausea, vomiting, and myalgias (especially in the knees) for a period of days. Tender hepatomegaly may also be present as well as
Faget’s sign, described as pulse-temperature dissociation whereby there is relative bradycardia despite high fevers. Moreover, the tongue may develop characteristic erythema along the tip and sides with a central white coating.

9. The second stage , or period of remission, follows with clinical improvement. For the vast majority (85%) of cases, the disease ends here. For the unlucky minority (15%), the respite ends after 48 hours. Amaryl mask : the patient’s face is purple, with a bluish tinge, eyes are anxious, bloodshot, sclera are injected, photophobia, lacrimation is noted. The oral mucosa is bright red, edematous.The pulse during this period is rapid, good filling. Heart tones are muted.
There are no abnormalities in the lungs.

10. The final stage , or period of intoxication, is marked by the return of symptoms seen in the first stage, but further complicated by jaundice, hemorrhage, oliguria, and metabolic encephalopathy. One unique feature of yellow fever is a predominantly AST elevated transaminitis as opposed to an ALT elevation typically seen with most viral hepatitides. Hemorrhage is a result of thrombocytopenia and inability to synthesize coagulation factors due to hepatic dysfunction. Morality rates for those that enter this stage ranges between 20-50%

11. Diagnosis ELISA to detect IgMAb
PCR to detect the presence of viral RNA A preliminary diagnosis is made based on:
1) Arrival or location in an endemic region(Africa and South America) – tropics andsubtropics;
2) symptoms of the disease (“saddle” or“two-wave” temperature curve, hemorrhagic syndrome, jaundice, kidney, liver and spleen damage);
3) Laboratory data: (in biochemistry – increase bilirubin, ALT, AST, urea, creatinine, in General the blood oppression shoots blood- reduction of leukocytes, neutrophils, lymphocytes, reduction of platelets, acceleration of sedimentation rate, urine protein,cylinders, erythrocytes)

12. Treatment Unfortunately limited to supportive care given that no known antivirals have been shown to be effective. As with other Flavivirus infections, no cure is known for yellow fever. Hospitalization is advisable and intensive care may be necessary because of rapid deterioration in some cases. Certain acute treatment methods lack efficacy: passive immunization after the emergence of symptoms is probably without effect; ribavirin and other antiviral drugs, as well as treatment with interferons, are ineffective in yellow fever patients. Symptomatic treatment includes rehydration and pain relief with drugs such as paracetamol (acetaminophen). Acetylsalicylic acid (aspirin) should not be given because of its anticoagulant effect, which can be devastating in the case of internal bleeding that may occur with yellow fever

13. Prevention Other control measures: Area around airport kept free of aedes > 400m Vector control (A. Aegypti) Mosquito nets Mosquito repellents Insecticide treatment of mosquito breeding sites
Wear proper clothing to reduce mosquito bites. When weather permits, wear long sleeves, long pants, and socks when outdoors. Yellow fever vaccine Live Attenuated Strain- 17 D
Diluent- cold physiological saline
Temp=- 30⁰C to +5⁰C Validity of certificate- 10 days to life long
Reaction to vaccination is minimal but in some cases it is sever

14. EYE (elimination yellow fever epidemic) Strategy (WHO,UNICEF,GAVI) Project at – risk population Prevent international spread of YF
Rapid containment of outbreak

15. Syndromes associated with yellow fever Intoxication Syndrome Jaundice syndrome Hemorrhagic syndrome Hepatolienial syndrome Hepatic insufficiency syndrome

16. Differencial diagnosis of yellow fever In a differential diagnosis, infections with yellow fever must be distinguished from: other feverish illnesses such as malaria. Other viral hemorrhagic fevers, such as Ebola virus, Lassa virus, Marburg virus, and Junin virus, must be excluded as the cause.

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