October 23, 2013

What Killed Them? Yellow Fever 1854

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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