I usually don’t post TWiM episodes here, but #90 has a lot of virology. In this episode, recorded in La Jolla, CA at the annual meeting of the Southern California Branch of the American Society for Microbiology, I first speak with Laurene Mascola, Chief of Acute Communicable Diseases at the Los Angeles County Department of Public Health. Dr. Mascola talks about how Los Angeles county has prepared for an outbreak of Ebola virus. Next up is David Persing, Executive Vice President and Chief Medical and Technology Officer at Cepheid. His company has developed an amazing, modular PCR machine that is brining rapid diagnosis everywhere, including the United States Post Office. And it might even be available on your refrigerator one day.

Watch TWiM #90 below, or listen at microbeworld.org/twim or iTunes.

 

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The Wild Types

29 October 2014

The Wild Types is an interview show about scientists hosted by Ushma Neill and Richard White. Ushma interviewed me for episode #2. The show name doesn’t refer to the fact that all scientists are wild (some are; I am not) but the genetic term referring to the strain or organism that is compared with mutants. As in, ‘the wild type virus was compared with the mutant virus that transmits among ferrets by the airborne route’.

 

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Peter L. SalkJonas Salk, who lead the team that developed the first poliovirus vaccine, was born 100 years ago today, 28 October 1914, in New York City. Numerous sites across the country have convened symposia in his honor. Last week City College of New York, where Salk earned a bachelor’s degree, held a centennial celebration. The photo shows Salk’s son Peter speaking at the celebration. New York University Medical Center, where Salk obtained his MD degree, also had a celebration last week. The Salk Institute, founded by Jonas Salk, will hold a celebration on 13 November. And today’s Google Doodle is in honor of Dr. Salk.

In honor of Salk’s memory, I’ve included below my interview with his son, Peter, and a list of all the articles on poliovirus from virology blog. If you can only read one, make it Dreaming of inactivated poliovirus vaccine. Then realize that WHO has called for a switch to Salk’s IPV.

Oral polio vaccine-associated paralysis in a child despite previous immunization with inactivated virus

Poliovirus escapes antibodies

Implications of finding poliovirus in sewers of Brazil and Israel

Polio-like paralysis in California

India has been free of polio for three years

World Polio Day

Poliovirus silently (and not so silently) spreads

The wall of polio

Poliovirus on Time

WHO will switch to type 2 inactivated poliovirus vaccine

Virology lecture: Picornaviruses

World Polio Day

Can India remain polio-free?

India polio-free for one year

Wild poliovirus in China

Transgenic mice susceptible to poliovirus

Poliomyelitis after a twelve year incubation period

Poliovirus vaccine safety

Is bivalent poliovirus vaccine a good idea?

Viruses and journalism: Poliovirus, HIV, and sperm

Poliovirus on BBC radio

Poliovirus type 2 returns

Polio returns to Minnesota

Poliovirus vaccine litigation

Polio among the Amish

Dreaming of inactivated poliovirus vaccine

Polio in Nigeria

Polio and Nobel Prizes

Polio in Pakistan and Afghanistan

Jonas Salk’s Poliovaccine

Poliovirus

Poliovirus is IRESistable

Vaccines lecture, 2014 (YouTube)

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On episode #308 of the science show This Week in Virology, Tom Solomon, an infectious disease doctor from Liverpool, talks with Vincent about viral central nervous system infections of global importance, Ebola virus, and running the fastest marathon dressed as a doctor.

You can find TWiV #308 at www.twiv.tv.

This morning I received this email from President Lee Bollinger:

Dear fellow members of the Columbia community:

As you may have seen in the media, Dr. Craig Spencer is being treated for Ebola at Bellevue Hospital in Manhattan. Dr. Spencer, an emergency department physician at NewYork-Presbyterian/Columbia University Medical Center, recently returned from a humanitarian mission with Doctors Without Borders to one of the outbreak areas in Western Africa. We admire and appreciate all of those willing to do this vital and selfless public health work around the globe.

It’s critical to bear in mind what our public health and infectious disease experts have emphasized – that the risk to people in New York City and at Columbia remains extremely low. If you or anyone has any concerns, please visit the University’s Ebola Preparedness site or the New York City Department of Health Ebola update page. You may also contact Student Health Services or Workforce Health and Safety for Faculty/Staff with Hospital Responsibilities.

We must keep Dr. Spencer in our thoughts and wish him a full and speedy recovery, as we do the vulnerable populations he serves. We will also continue to keep the Columbia community informed as we learn more from City, State, and Federal health officials.

Sincerely,
Lee C. Bollinger

The transition between incubation period (when there are no symptoms) and the first clinical signs is a dangerous period. During this time the patient may continue to move around in public despite having fever and other indications of infection. It will be important to trace as many of this physician’s contacts as possible, a difficult task in a city of over 8 million people. Apparently the physician traveled around the city, using the subways, the night before having a fever. Whether any virus is shed during this time, in amounts sufficient to infect others, is unknown, but could be determined by studying the contacts of such infected individuals.

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crab eating macaqueI have received many questions about whether immunizing with Reston virus could protect against infection with Ebola virus. Usually the question comes together with the statement ‘because Reston virus does not cause disease in humans’. I can think of two reasons why a Reston virus vaccine is not a good idea.

There have been very few confirmed human infections with Reston virus (4 according to Fields Virology 6th Edition), and although these individuals did not show signs of disease, the number is too small to make any conclusions. For example, if the case fatality ratio of Reston virus in humans were 1%, we might not have yet seen any deaths due to the small number of confirmed infections. However if we were to immunize a million people with a Reston virus vaccine, and the case fatality ratio were 1%, there would be 10,000 deaths, obviously an unacceptable rate for a vaccine. As the virus causes disease in nonhuman primates, and there are so few human infections, it is not possible to know the case fatality ratio.

The other problem is that in general, infection with one of the Ebolaviruses does not confer protection against the others*. For example, animals that survive challenge with Ebola virus (Zaire) are not protected from infection with Sudan virus. For this reason, vaccines need to be prepared against representatives of all the species. I am not aware of any animal studies that have assessed whether Reston virus infection protects from infection with the other Ebolaviruses, but there is no reason to believe that such cross-protection would be achieved.

Vaccines are currently being tested against Ebola virus (species Zaire ebolavirus), cause of the outbreak in west Africa.

*Thanks to Andrea Marzi for information on cross-protection.

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When the first case of Ebola virus infection was detected at the Firestone Liberia, Inc. rubber tree plantation in March of this year, the company needed to prevent the virus from spreading among their 8,500 employees. The company established an incident management system, developed procedures for early detection of infection, enforced infection control guidelines, and provided different levels of management for contacts depending on their exposure. The company did a remarkable job of isolating and caring for patients and limiting transmission to health care workers and family members. A description of this program, just issued by Morbidity and Mortality Weekly Report, is a must read.

I found the following paragraph, Community Reintegration of Ebola Survivors, perhaps the most significant in the report:

To prepare communities for the return of Ebola survivors and minimize potential stigmatization, Firestone established a survivor reintegration program. The program consisted of community education, whereby members of the reintegration team explained that the survivor had been declared Ebola-free and no longer contagious, and a survivor welcome celebration. The celebrations were prepared by the community with assistance from the reintegration team and attended by MOHSW, Firestone staff, and clergy. Each survivor was presented a medical certificate and an opportunity to share his or her experience. The celebrations were broadcast on radio and recorded for future programs for Ebola education in the community. In addition, Firestone donated a solidarity package to the survivor, which included essential household items (e.g., mattress, bedding material, and mosquito net).

Among all our discussion of virus fatality, transmission, virulence, fomites, and vaccines, we should remember that people are contracting the virus. At all stages of disease they need to be treated with humanity.

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SkinI received this question about Ebola virus infection via email:

Can you become infected if infected droplet lands on your skin even if there is no abrasion on the skin? I am now hearing this, which surprises me. The virus can enter through the actual skin and does not need mucus membrane to enter?

The skin of most animals is an effective barrier against viral infections. The outer layer of human skin, called the stratum corneum, consists of a layer of dead, keratinized cells (illustrated). Viruses cannot replicate in, or be transported across, dead cells. Therefore any virus that lands on the skin cannot simply replicate in the outer layer or be transported to the underlying living cells.

However, viruses can pass through the dead layer of the skin through cuts or abrasions. Many activities, such as shaving, or even scratching, lead to microabrasions. It is relatively easy to breach the dead layer of cells with a fingernail, and such abrasions cannot be seen.

A patient in the late stages of Ebola virus infection (such as the Dallas patient) is shedding high amounts of virus particles in body fluids. If virus-laden droplets land on the skin, the virus can readily enter via cuts or abrasions. Even if the skin is intact, the droplets could be inadvertently transferred to mucous membranes of the eye, nose, or mouth, initiating infection. For this reason it is important that the skin be entirely covered when caring for Ebola virus infected patients.

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TWiV 307: Ebola aetiology

19 October 2014

On episode #307 of the science show This Week in Virology, Tara Smith joins the TWiEBOVsters to discuss the Ebola virus outbreak in west Africa, spread of the disease to and within the US, transmission of the virus, and much more.

You can find TWiV #307 at www.twiv.tv.

Cost BalancingWHO and CDC recommend that individuals who are potentially infected with Ebola virus should be quarantined for 21 days. Where does this number come from? Charles Haas at Drexel University asked the same question, and provides an answer.

The quarantine period for an infectious disease is based on the incubation period, the time before symptoms of an infection appear. For Ebola virus, the incubation period is 2-21 days after infection. During this time it is believed that individuals infected with the virus are not contagious, but they could produce small amounts of virus. Whether or not a patient is contagious during the incubation period depends on the virus.

It is clearly important to determine the correct quarantine period for Ebola virus to prevent chains of infection. The longer the quarantine period imposed, the less risk of infecting others. However the cost of enforcing quarantine must be balanced with the cost of releasing exposed individuals (illustrated). According to Haas, the optimal quarantine time should be at the intersection of the two curves.

To determine how the Ebola virus quarantine period was set at 21 days, Haas examined the incubation periods calculated for previous outbreaks. In a study of the 1976 Zaire outbreak, the mean time between exposure and disease for 109 cases of person-to-person spread was calculated at 6.3 days with a range of 1 to 21 days. Mean incubation times for the 1995 Congo outbreak (315 cases) and the 2000 Uganda outbreak (425 cases) were 5.3 and 3.35 days, respectively. Two other analyses of the 1995 Congo outbreak gave mean incubation times of 10.11 and 12.7 days. WHO has estimated a mean incubation period for the first 9 months of the current west African outbreak as 11.4 days, with an upper limit (95% confidence) of 21 days.

Haas concludes that the 21 day quarantine value is derived from a ‘reasonable interpretation’ of outbreak data, but it might not be long enough. He estimates that there is a risk of between 0.2% and 12% of developing Ebola virus infection after 21 days.

The current outbreak should allow collection of data for revising and updating the 21 day quarantine period for Ebola virus infection.

 

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