Several years ago I read a book called ‘The Hot Zone’ by Richard Preston. It’s a thriller about a 1989 Ebola virus outbreak in monkeys at a quarantine center near Washington, DC. It reads like a Michael Crichton novel, but it’s a true story. The monkeys, imported from the Philippines, died from Ebola hemorrhagic fever and many people were exposed. There was great concern about an Ebola epidemic in the US. But nature is full of surprises, and (spoiler alert) the monkeys had a strain of Ebola that did not cause illness in humans.
People infected with other Ebola strains have not been so lucky. The first outbreaks occurred in Zaire and Sudan in 1976. Over 600 people were infected with an astonishing 88% mortality rate. Over the next 35 years there have been multiple outbreaks in Africa. In many of these outbreaks, the first human infection occurred by contact with an infected monkey or chimpanzee. Fruit bats are the most likely reservoir where the virus continues to circulate between outbreaks.
The 2014 Ebola crisis is something we have never seen before. This is by far the largest and most severe Ebola epidemic that the world has ever seen. Guinea, Sierra Leone, and Liberia are the countries most affected at this time. The rapid spread of Ebola has caused a humanitarian crisis in West Africa and a threat to global security. Unlike all prior Ebola outbreaks, this one is affecting urban populations and crossing national boundaries. Health care systems in affected countries are unprepared and overwhelmed; the governments have no resources and critical supplies are not available. The international community has been slow to respond, and the case count is increasing exponentially. CDC computer simulations suggest that over a million cases could occur over the next few months, but the estimates are highly uncertain. It will take a long time to get this under control, and it will require an unprecedented level of international support and coordination. The United States and Europe have the resources and capacity to contain Ebola effectively, but many poorer countries do not. Rapid deployment of a safe and effective vaccine is urgently needed.
We also have an epidemic of Ebola anxiety in the United States. This is not surprising given the 24/7 news media coverage of the cases in Dallas and some highly publicized missteps by the health care system. Ebola is a scary disease, and most people don’t know much about it. A recent poll found that more than 4 in 10 Americans are worried that they or a family member might catch Ebola. Schools have been closed in some communities, and two states instituted a quarantine of all returning health care workers against the advice of CDC and infectious disease experts. A teacher in Maine was forced to take a leave of absence just because she attended a conference in Dallas---she was nowhere near the hospital where the Liberia patient was treated. In Mississippi, a group of parents pulled their children out of school after they learned that the principal had travelled to Zambia, a country that does not have any Ebola cases. These responses, although not typical, reflect the high level of public anxiety and misinformation about Ebola in the United States.
So what are the facts? Should we get ready for an Ebola epidemic in the United States? Here is a brief review of what we know and don’t know:
- Ebola is not easy to catch. It is not like the flu. It does not spread through the air, and you won’t get it from being in the same room with a patient. You can become infected with Ebola if you get blood, vomit, diarrhea, urine, or other body fluid from a victim on your skin or a mucous membrane. Contact with contaminated clothing, bedding or other objects can also pose a risk. Respiratory droplets from sneezing or coughing may pose a risk. Ebola is NOT spread through food, water, or casual contact. It is not a risk in the community----schools, churches, public transportation, sporting events, etc. However, Ebola is a serious risk for doctors and nurses who are caring for critically ill patients. The cases in Dallas demonstrated that specialized Ebola training and equipment are needed, even in US hospitals. We learned a lot from the experience in Dallas, and the response to the recent Ebola case in New York City was much improved.
- Ebola does not spread from people who do not have symptoms. The incubation period for Ebola can range from 2 to around 21 days, but symptoms commonly develop 8 to 10 days after exposure. Patients do not spread the virus before symptoms develop. However, people who have been exposed to Ebola need to be isolated until it is known whether they are infected.
- An epidemic of Ebola in the United States is extremely unlikely. It is possible, even likely, that more Ebola cases will arrive in the US from West Africa. Flight restrictions will not prevent this from happening. The good news is that hospitals are now more prepared to deal with suspected Ebola cases, and patients will be screened to rapidly identify suspected cases. Contact tracing and isolation (when appropriate) will be used by CDC and state public health agencies to prevent further spread after a case is identified. Ebola has a low reproduction rate (average number of people infected by a sick person) and a relatively long incubation period. That makes it is easier to contain compared to diseases like measles or chickenpox.
- There is no treatment for Ebola, but intensive care medicine can improve survival. Ebola kills people before the body has time to mount an immune response. If you survive Ebola, you will be immune. Early aggressive treatment in the ICU to maintain fluid and electrolyte balance can improve survival. In the US, Ebola treatment will occur at hospitals with specialized facilities and training. Several experimental medications are in development, but none have been adequately tested in humans. Still, the situation is so dire in West Africa that a WHO panel said that use of these drugs is ethical even though their effectiveness and safety are unproven.
- Vaccines are being tested and hold promise for controlling Ebola in Africa. A safe and effective vaccine is the key to stopping the current epidemic and preventing future ones. There are at least 2 vaccines in the pipeline that provide 100% protection against Ebola in monkeys, but we don’t know if they will protect humans. Initial human studies to assess safety have started, and larger human studies are planned to measure antibody response and protection. The timeline is being accelerated in the hope that mass production of a vaccine could begin in 2015. However, it is difficult to study an experimental vaccine in the middle of an epidemic, and the ethics of a placebo-controlled trial are still being debated. Even if the ethical issues are resolved (and they will be), the logistics of launching a complex clinical trial will be daunting in countries without a functional government or health care infrastructure.
- We already know a lot about Ebola, but there are gaps in our knowledge. We know that contact with blood or body fluids is a risk factor, but we do not understand exactly how this occurs. We don’t know much about how long Ebola virus survives outside the body in different environments. Why do some patients die and others survive? How will different control measures affect the epidemic? The virus is mutating, but we don’t understand how those mutations will affect the risk of transmission or the severity of the disease. There is an urgent need for more research on virus evolution, factors influencing transmission and virulence, and impact of countermeasures.
Marshfield Clinic has assembled a team of experts to plan and prepare for the unlikely event of an Ebola case in central or northern Wisconsin. If a suspected case is found, appropriate steps will be taken to protect patients and medical personnel. Marshfield Clinic will work closely with state and federal agencies to ensure that appropriate public health measures are taken to prevent transmission.
There are many reasons to be concerned about Ebola, but we need to keep the risk in perspective. There have been very few cases of Ebola in the United States. Thousands die each year from influenza, and we have a vaccine for that. If you want to do something about Ebola, consider making a donation to an organization (such as Doctors without Borders) that is providing medical care for patients in Africa. And don’t forget to get a flu shot.