What does Ebola actually do?

The Pathogenesis of Ebola

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We've heard of the horrors of Ebola. 

What's really horrible is how Ebola can hide Ebola.

Ebola starts off like the flu. Within 2 weeks, it deserves its horrid reputation. It does this by cloak and dagger. Ebola dresses up as a soldier, joins our defenses, infects those cells and individuals meant to protect us - in our immune systems, hospitals, homes.

Ebola enters unnoticed, cloaked

Ebola's entry is often silent.

It spreads through contact with body fluids (blood, saliva, stool, urine, sweat-skin or their droplets) or dirty sheets, clothing, protective gear. It's not water, food, or airborne. It can enter many ways - breaks in the skin, mucus membranes, needlesticks. Many do not know exactly how they were infected.

Ebola first dons a soldier's uniform when it infects cells called macrophages and dendritic cells - our immune system watchtower guardians. Instead of responding to the threat, they become part of it. 

Dendritic cells command our immune system. They normally send our warning signals and present antigens, which for the immune system is like giving a dog a scent to follow. In Ebola, they do not. They do not mature; they become infected and release virus. 

Macrophages should present antigens too. Infected macrophages instead transmit jumbled cytokine signals, producing misdirected immune responses.

This immune response helps create the illness - "septic shock", fever, weakness, low blood pressure, leaking blood vessels - that is Ebola.

Ebola comes with tools to evade notice. Ebola Viral Protein 24 blocks interferon cell signaling which would been a distress signal. Viral Protein 35, hides double strained RNA which would've been recognized as not human.

The virus released from infected guardian cells clandestinely passes through our immune system -lymph nodes, then spleen, thymus. It infects many cell-types and invades the liver, adrenal glands, leading to organ dysfunction, causing problems clotting and low steroid levels that lower blood pressures. It escapes recognition and reaches into endothelial, epithelial cells, and even the brain.

In this mix, other troops, Lymphocytes that fight viruses, elect to self-destruct, without being infected. 

Meanwhile the disease is unnoticed

Ebola hides in plain sight, then infects those who care for us.

Someone infected will initially be symptom-free and at the same time, non-infectious, as Ebola passes through lymph nodes and the spleen before reaching blood and body fluids. Although not infectious, they may travel elsewhere unaware.

The illness begins abruptly and inconspicuously. Ebola develops about 6 days after a needlestick, 8-10 days after contact (4-10, possibly 2-21 days). 

Ebola may be mistaken for another illness.

Initial symptoms include flu-like body aches, fever, tiredness, joint pains, sore throat. Patients will not know the risk they pose. As illness worsens, it may seem like the flu or malaria. They may seek medical care, infecting unaware caregivers, who then infect patients and co-workers.

Just like with our immune systems, those meant to protect may spread the illness. Deaths often occur from exposures through hospitals or homecare.

After 5 days of illness, Ebola begins to emerge. A patient may vomit, have watery diarrhea. It may be mistaken - as in 2014 - for cholera. It may also be mistaken for other diarrheal diseases, like typhoid.

Signs of Ebola may be unnoticed - like hiccups or bloodshot eyes. An upper body rash with red bumps and peeling may be seen, but not on those with darker skin. There may be unseen dark coloration on the palate. Some have hearing loss, ear-ringing.

Women may miscarry, with copious blood-loss contaminating caregivers.

Others develop encephalitis - brain inflammation, seizures, expressionless faces. They become confused, behave irrationally, infect those who calm their agitation.

Some, but not all, develop bleeding. It may be simple bruising or bleeding from a needle prick. This may seem like Lassa fever in West Africa. 

Next..

It cannot be detected in a lab (through PCR) until after symptoms begin, and usually at least 3 days after symptoms begin.

Those who improve usually do so in their 2nd week of illness. Viral load drops. Antibodies form. Survival improves with hydration (oral, IV). Survival ranges 10-60+%.

Many do not create antibodies. Viral levels rise unchecked. Tissues die. Death usually occurs after 1-2 weeks from multiorgan failure, septic shock. Kidneys, livers, hearts fail; blood pressure drops; urination stops; fluid drowns lungs.

What we know

For safety, blood tests and monitoring are minimized. Intensive care monitoring has been reported on only one patient. Data are limited.

We know fevers rise, blood pressure - initially normal - drops. White count (lab value) drops (low lymphocytes, then rising neutrophils). Platelets drop (50-100). Potassium, Sodium are abnormal. Kidney function worsens; protein is in the urine. Liver tests worsen, especially AST, coagulation.

What we don't know

We are learning much about this disease - how to optimize care and best halt transmission.

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