In 1854 Dr John W Comfort, age 32, died of Yellow Fever in
New Orleans leaving his wife with 3 young children. Further investigation
identified a horrific epidemic in numerous southern port cities in the mid
1850s with New Orleans losing 10% of its population to this infection in 1853
with thousands more succumbing in 1854-5. The cause was not known and no cure
existed. It made me wonder why Yellow
Fever had been such a scourge and why we don’t hear much about it today.
Accounts
from individuals present in New Orleans depict a very grim picture of a disease-ridden
city filled with the stench of dying and dead bodies in the heat of the summer.
The city’s business leaders tried to keep the news quiet as they feared the
entire city would be quarantined in an effort to prevent the spread of the
disease upriver. Mobile, Charleston, even Philadelphia and Baltimore were
infected – port cities !
It is believed that the disease originated in Africa and was
introduced to Europe and the Americas by the slave trade. The first definitive
report was from Barbados in 1647 and soon thereafter from the Yucatan Peninsula
where the disease was called “ blood vomit”.
Patients have fever, convulsive black vomit and develop jaundice as the
liver fails (hence, Yellow Fever). Decades passed before the cause was
identified and a vaccine developed.
In 1881, a Cuban physician, Carlos Finlay, proposed that Yellow
Fever might be transmitted via mosquitoes, but received a cool reception from the
medical community at the time. A team
led by the now famous Walter Reed, (prompted by heavy losses from the disease
in the Spanish-American war) finally confirmed Finlay’s hypothesis in 1901
subsequently leading to the eradication of yellow fever first in Havana and
then later during the construction of the Panama Canal.
Yellow fever is a viral disease that is endemic (present at
a fairly constant rate) in Africa and South America and transmitted
to humans by the bite of female mosquitoes of the Aedes species in Africa and Haemagogus
species in South America. The bite of an infected female mosquito introduces virus
particles under the skin where replication occurs before spreading via the
lymphatic system and bloodstream to the major organs. Symptoms of Yellow Fever start after an
incubation period of 3 to 6 days and most non-vaccinated people in endemic
areas will suffer a mild infection with fever, chills, backache, headache,
nausea and vomiting lasting 3 to 4 days; no jaundice is seen. This acute phase
is followed by a period of remission of about two days where symptoms abate and
recovery is seen. However, in about 15%
of individuals in whom recovery seems apparent, a second ‘toxic’ phase occurs
with recurring fever, nausea, liver injury and jaundice, kidney injury and characteristic
black vomit due to stomach bleeding.
Death, due to multi-organ failure, generally follows in 7 to 10 days killing
20-30% of native Africans who enter this toxic phase, and 50-60% of native
South Americans. Surviving the infection
confers life-long immunity and typically no permanent organ damage occurs.
The Yellow Fever virus was first isolated in 1927 from a
diseased patient in Ghana. This led to
the development of a vaccine in 1936 by Max Theiler, a South African microbiologist
working at the Rockefeller Institute in NYC, who received the Nobel Prize in
1951 for this achievement. Immunity
against all forms of the virus occurs in nearly 100% of vaccinated individuals,
lasting for at least 10 years. Since
World War II, mainly because of effective vaccination programs, yellow fever is
only rarely seen in travelers returning to Europe and North America. Yellow fever has never
appeared in Asia. Today, there still is
no cure or specific antiviral therapy.
Many thanks to microbiology expert, Dr CJ, for scientific content
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