Scientists, share your Zika virus reagents!

FlavivirusToday I learned that a number of investigators refuse to share their samples of Zika virus with other laboratories.

There are countless stories about scientists not sharing reagents because they want to be the first to make a discovery. This behavior allows them to publish first, secure more grant funding, garner invitations to speak at meetings, and generally stroke their egos.

This sort of selfish behavior happens all the time in science, but it is particularly offensive at a time when a new virus is spreading rapidly, and we need information about its biology, pathogenesis, and epidemiology to be able to treat and prevent infections. Not sharing reagents means that advances will come more slowly, or perhaps not at all: how do you know which laboratory will make the crucial findings?

Science has enough of a public image problem already. Do we need to make it worse by not sharing materials to work on a virus that has rapidly entered the public’s eye, and about which there are so many unanswered questions?

By keeping reagents to their own laboratories, scientists are being short-sighted and narrow-minded. Will you be pleased when you need a reagent and you can’t obtain it from another source?

Dear fellow scientists: scientific research is not about you and your ego. It is about contributing to human health. Get with the program.

 

Zika virus and microcephaly

FlavivirusThree reports have been published that together make a compelling case that Zika virus is causing microcephaly in Brazil.

An epidemic of Zika virus infection began in Brazil in April 2015, and by the end of the year the virus had spread through 19 states, many in the northeastern part of the country. Six months after the start of the outbreak, there was a surge in the number of infants born with microcephaly. It was not known if most of the mothers had been infected with Zika virus, as results of serological tests, virus isolation, or PCR were not available.

An initial report of 35 Brazilian infants with microcephaly born to women who either resided in or traveled to areas where Zika virus is circulating revealed that 74% of mothers had a rash (one sign of Zika virus infection) in the first or second trimester. At the time of this study no laboratory confirmation of Zika infection was available, but the infants did not have other infections associated with birth defects, including syphilis, toxoplasmosis, rubella, cytomegalovirus or herpes simplex virus.

Yesterday the CDC reported on the analysis of tissues from two infants with microcephaly who died within 20 hours of birth, and two miscarriages, all from the state of Rio Grande do Norte in Brazil. The mothers all had rashes typical of Zika virus infection in the first trimester of pregnancy, but were not tested for infection.

All four specimens were positive for Zika virus RNA by polymerase chain reaction (PCR) done with primers from two different regions of the viral RNA. Staining of tissues with anti-viral antibodies revealed the presence of viral antigens in two of the four samples, in the brain of one newborn and in the placenta from one of the miscarriages.

A second report from the University of Sao Paulo documents ocular abnormalities in Brazilian infants (from the state of Bahia) with microcephaly and presumed Zika virus infection. The mothers of 23 of 29 infants (79.3%) with microcephaly reported signs of Zika virus infection (rash, fever, joint pain, headache, itch, malaise). Of these, 18 (78.3%) had symptoms during the first trimester of pregnancy, 4 (17.4%) during the second trimester, and 1 (4.3%) during the third trimester.

No laboratory results were available to confirm Zika virus infections, but toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, syphilis, and HIV were ruled out.

Abnormalities of the eye were found in 10 of 29 (34.5%) of infants with microcephaly. These included focal pigment mottling, chorioretinal atrophy, optic nerve abnormalities, displacement of the lens, or a hole in the iris.

These observations suggest that Zika virus infection may also cause lesions of the eye, although confirmation of infection needs to be done to prove causation. This uncertainty is reflected in the title of the article: “Ocular findings in infants with microcephaly associated with presumed Zika virus congenital infection in Salvador, Brazil” (italics mine).

The final paper is, in my opinion, the blockbuster. In this single case report, a 25 year old European woman working in Natal, Brazil, became pregnant in February 2015. In the 13th week of gestation she had fever, muscle and eye pain, and rash. Ultrasound in Slovenia at 14 and 20 weeks revealed a normal fetus.

At 28 weeks of gestation fetal abnormalities were detected, including microcephaly, and the pregnancy was aborted. Autopsy revealed severe brain defects, and 42 to 54 nm virus particles were detected in the brain by electron microscopy.

Infection with a variety of microbes was ruled out, but Zika virus RNA was subsequently detected in brain tissue by PCR.

Here is the clincher – the entire Zika virus genome was identified in brain tissue by next-generation sequencing! Analysis of the sequence revealed 99.7% nucleotide identity with a Zika virus strain isolated from a patient from French Polynesia in 2013, and a strain from Sao Paulo from 2015. These findings agree with the hypothesis that the current Brazilian outbreak was triggered by a virus from Asia.

Up to now there have been few data that strongly link Zika virus infection to congenital birth defects. Of these three new studies, the recovery of a full length Zika virus genome from an infant with microcephaly is the most convincing. Given the rapidity by which new data are emerging, it seems likely that additional evidence demonstrating that Zika virus can cause microcephaly will soon be forthcoming.

I’m amazed that a flavivirus can cause birth defects – when no flavivirus has done so before*. This is a virus spread by mosquitoes, and to which most of the world is not immune. The Zika virus outbreak will surely test our ability to respond rapidly with substantial mosquito control, diagnostics, antivirals, and a vaccine.

Update 2/11/16: A second paper has been published documenting ocular abnormalities in ten infants born to mothers in Brazil who had symptoms consistent with Zika virus infection.

Update 2/12/16: *Japanese encephalitis virus and West Nile virus have been shown to cross the placenta and infect the fetus. Such events must be rare because a larger association with birth defects has not been reported.

TWiV 375: Zika and you will find

TWiVOn episode #375 of the science show This Week in Virology, the TWiVziks present everything you want to know about Zika virus, including association of infection with microcephaly and Guillain-Barré syndrome, transmission, epidemiology, and much more.

You can find TWiV #375 at microbe.tv/twiv.

Zika from sex, the byway but not the highway

FlavivirusCan Zika virus be sexually transmitted? Perhaps in very rare cases, but the main mode of transmission is certainly via mosquitoes. That’s why I’ve shamelessly stolen a quote on this topic from Dr. William Schaffner of Vanderbilt University:

Mosquito transmission is the highway, whereas sexual transmission is the byway. Sexual transmission cannot account for this sudden and widespread transmission of this virus.

If you just read the news headlines, which many people do, you will think that Zika virus spreads like HIV. But it does not.

Let’s make a clear distinction between sexually transmitted viruses (like HIV – sex is the main mode of transmission, along with contaminated blood), versus sexually transmissible viruses. The latter includes viruses that now and then might be sexually transmitted under certain circumstances, but which normally are transmitted by another route. Zika virus is transmitted among humans by mosquitoes. If sexual transmission occurs, it is very, very rare, given the large number of Zika virus infections that have been documented.

Is Zika virus sexually transmissible?

The first hint of sexual transmission of Zika virus came from the story of two American scientists working in Senegal in 2008, where they were sampling mosquitoes. Between 6-9 days after returning to their homes in Colorado, they developed a variety of symptoms of infection including fatigue, headache, chills, arthralgia, and a maculopapular rash. The wife of one patient had not traveled to Africa, yet she developed similar symptoms three days after her husband. Analysis of paired acute and convalescent sera from all three patients revealed antibodies against Zika virus. The authors of the study do not conclude that transmission from husband to wife was via sexual activity – they suggest it as a possiblity. Their data could not prove sexual transmission.

More recently infectious Zika virus was detected in semen of a French Polynesian male who had recovered from infection. The presence of virus in semen is compatible with sexual transmission, but the patient was not known to have transmitted infection to anyone.

The CDC has concluded that Zika virus was transmitted to an individual in Texas who had sex with a traveler returning from Venezuela. As of this writing I do not know exactly how the CDC came to this conclusion.

What would be needed to prove that Zika virus is sexually transmissible?

Polymerase chain reaction (PCR) is used to diagnose many viral diseases. This assay detects small fragments of viral nucleic acid and can be very specific. However as we are trying to establish for the first time that Zika virus can be transmitted sexually, more than PCR must be done – infectious virus should be recovered from the donor and recipient. A positive PCR result does not mean that infectious virus is present in the sample, only fragments of the genome, which of course would not be infectious. It is important to correlate the presence of infectious virus with sexual transmission.

Not only should infectious virus be recovered from both donor and recipient, but the viral genome sequences should be nearly identical, providing strong evidence for sexual transmission. If the viral genome sequences were substantially different, this result could imply that the infection was acquired from someone else.

Looking for anti-viral antibodies in serum is a good way to confirm virus infection when virus is no longer present. However it is not as specific as PCR or virus isolation, and does not provide information about the genome of the donor and recipient virus.

Sexual transmission of Ebolavirus still remains speculative. There are several suspected cases, and many examples of PCR positive semen samples from men who have recovered from the disease. It’s not easy to prove that a virus can be transmitted sexually, especially when it is a rare event.

Just as we are not sure that Zika virus causes microencephaly, we are not sure if it can be sexually transmitted.

TWiV 374: Discordance in B

TWiVOn episode #374 of the science show This Week in Virology, the TWiVniks consider the role of a cell enzyme that removes a protein linked to the 5′-end of the picornavirus genome, and the connection between malaria, Epstein-Barr virus, and endemic Burkitt’s lymphoma.

You can find TWiV #374 at microbe.tv/twiv.

Zika virus

FlavivirusThe rapid spread of Zika virus through the Americas, together with the association of infection with microcephaly and Guillain-Barré syndrome, have propelled this previously ignored virus into the limelight. What is this virus and where did it come from?

History
Zika virus was first identified in 1947 in a sentinel monkey that was being used to monitor for the presence of yellow fever virus in the Zika Forest of Uganda. At this time cell lines were not available for studying viruses, so serum from the febrile monkey was inoculated intracerebrally into mice. All the mice became sick, and the virus isolated from their brains was called Zika virus. The same virus was subsequently isolated from Aedes africanus mosquitoes in the Zika forest.

Serological studies done in the 1950s showed that humans carried antibodies against Zika virus, and the virus was isolated from humans in Nigeria in 1968. Subsequent serological studies revealed evidence of infection in other African countries, including Uganda, Tanzania, Egypt, Central African Republic, Sierra Leone, and Gabon, as well as Asia (India, Malaysia, Philippines, Thailand, Vietnam, Indonesia).

Zika virus moved outside of Africa and Asia in 2007 and 2013 with outbreaks in Yap Island and French Polynesia, respectively. The first cases in the Americas were detected in Brazil in May 2015. The virus circulating in Brazil is an Asian genotype, possibly imported during the World Cup of 2014. As of this writing Zika virus has spread to 23 countries in the Americas.

The virus
Zika virus is a member of the flavivirus family, which also includes yellow fever virus, dengue virus, Japanese encephalitis virus, and West Nile virus. The genome is a ~10.8 kilobase, positive strand RNA enclosed in a capsid and surrounded by a membrane (illustrated; image copyright ASM Press, 2015). The envelope (E) glycoprotein, embedded in the membrane, allows attachment of the virus particle to the host cell receptor to initiate infection. As for other flaviviruses, antibodies against the E glycoprotein are likely important for protection against infection.

Transmission
Zika virus is transmitted among humans by mosquito bites. The virus has been found in various mosquitoes of the Aedes genus, including Aedes africanus, Aedes apicoargenteus, Aedes leuteocephalus, Aedes aegypti, Aedes vitattus, and Aedes furcifer. Aedes albopictus was identified as the primary vector for Zika virus transmission in the Gabon outbreak of 2007. Whether there are non-human reservoirs for Zika virus has not been established.

Signs and Symptoms
Most individuals infected with Zika virus experience mild or no symptoms. About 25% of infected people develop symptoms 2-10 days after infection, including rash, fever, joint pain, red eyes, and headache. Recovery is usually complete and fatalities are rare.

Two conditions associated with Zika virus infection have made the outbreak potentially more serious. The first is development of Guillain-Barré syndrome, which is progressive muscle weakness due to damage of the peripheral nervous system. The association of Guillain-Barré was first noted in French Polynesia during a 2013 outbreak.

Congenital microcephaly has been associated with Zika virus infection in Brazil. While there are other causes of microcephaly, there has been a surge in the number of cases during the Zika virus outbreak in that country. Whether or not Zika virus infection is responsible for this birth defect is not known. One report has questioned the surge in microcephaly, suggesting that it is largely attributed to an ‘awareness’ effect.  Current epidemiological data are insufficient to prove a link of microcephaly with Zika virus infection. Needed are studies in which pregnant women are monitored to see if Zika virus infection leads to microcephaly.

Given the serious nature of Guillain-Barré and microcephaly, it is prudent for pregnant women to either avoid travel to areas that are endemic for Zika virus infection, or to take measures to reduce exposure to mosquitoes.

Control
There are currently no antiviral drugs or vaccines that can be used to treat or prevent infection with Zika virus. We do have a safe and effective vaccine against another flavivirus, yellow fever virus. Substituting the gene encoding the yellow fever E glycoprotein with that from Zika virus might be a good approach to quickly making a Zika vaccine. However testing of such a vaccine candidate might require several years.

Mosquito control is the only option for restricting Zika virus infection. Measures such as wearing clothes that cover much of the body, sleeping under a bed net, and making sure that breeding sites for mosquitoes (standing water in pots and used tires) are eliminated are examples. Reducing mosquito populations with insecticides may also help to reduce the risk of infection.

Closing thoughts
It is not surprising that Zika virus has spread extensively throughout the Americas. This area not only harbors mosquito species that can transmit the virus, but there is little population immunity to infection. Infections are likely to continue in these areas, hence it is important to determine whether or not Zika virus infection has serious consequences.

Recently Zika virus was identified in multiple states, including Texas, New York, and New Jersey, in international travelers returning to the US . Such isolations are likely to continue as long as infections occur elsewhere. Whether or not the virus becomes established in the US is a matter of conjecture. West Nile virus, which is spread by culecine mosquitoes, entered the US in 1999 and rapidly spread across the country. In contrast, Dengue virus, which is spread by Aedes mosquitoes, has not become endemic in the US.

We recently discussed Zika virus on episode #368 of the science show This Week in Virology. You can be sure that we will revisit this topic very soon.

Added 1/28/16 9:30 PM: The letter below to TWiV provides more detail on the situation in Brazil.

Esper writes:

Hi TWIVomics

I hope this email finds you all well and free of pathogenic viruses.

My name is Esper Kallas, an ID specialist and Professor at the Division of Clinical Immunology and Allergy, University of São Paulo, Brazil.

I have been addicted to TWIV since a friend from U. Wisconsin participated in the GBV-C episode (David O’Connor, episode #260). Since then, never missed one episode. After long silent listening, I decided to write for the first time, motivated by the ongoing events in my country, potentially related to the Zika virus.

In the last episode, Emma wrote about events taking place in the small town of Itapetim, State of Pernambuco, Northeastern Brazil, which I will describe a bit later in this email. Before, let me bring some background information on the current situation.

Most believed Zika was a largely benign virus, causing a self-limited disease, clearly described in episode #368. Its circulation was documented after an outbreak became noticed in the State of Bahia (NE Brazil) by a group led by Guilherme Ribeiro, a talented young Infectious Diseases Scientist from Fiocruz (PMID: 26584464, Emerg Infect Dis. 2015 Dec;21(12):2274-6, free access)

However, things started to get awkward around October 2015, when a single hospital in Recife (NE Brazil) and some other practicing Obstetricians and Pediatricians from the region started reporting a mounting number of microcephaly cases in newborns, later confirmed by the national registry of newborns. The numbers are astonishing. The graph below depicts the number of cases per year prior to the surge in 2015. Only this year, 2,975 cases were reported by December 26, the vast majority in the second semester of the year. Cases are concentrated in the Northeast (map), with 2,608 cases, including 40 stillbirths or short living newborns.

Microcephaly, Brazil

In response to the situation, the Brazilian Ministry of Health has declared a national public health emergency (http://portalsaude.saude.gov.br/index.php/cidadao/principal/agenciasaude/20629-ministerio-da-saude-investiga-aumento-de-casos-de-microcefalia-em-pernambuco).

The Brazilian Ministry of Health has been presenting updates every week (see link: http://portalsaude.saude.gov.br/index.php/o-ministerio/principal/leia-mais-o-ministerio/197-secretaria-svs/20799-microcefalia). It is important to observe some imperfections in these numbers: 1. There may be an over reporting after the news made to the big media, suggesting an association between microcephaly and Zika virus. 2. The criterion to consider a microcephaly case has been changed after the current epidemic from 33cm to 32cm; this is because 33cm of head circumference is sitting in the 10th percentile of newborns at 40 weeks of pregnancy and the adjustment would bring the limit to the 3rd percentile, increasing the specificity to detect a true microcephaly case (this may result in an over reporting in the beginning of the epidemic).

The association between Zika virus infection and microcephaly was suspected since the beginning, when Brazilian health authorities ruled out other potential causes, together with the fact that the microcephaly epidemic followed Zika virus spread. Further evidences were the two positive RT-PCR for Zika RNA in two amniotic fluids obtained from two pregnancies of microcephalic fetuses and a stillborn microcephaly case with positive tissues for Zika RNA. In fact, French Polynesia went back to their records and also noticed an increase of microcephaly case reporting, following their epidemic by the same virus strain in 2013 and 2014.

Now, Zika virus transmission has been detected in several countries in the Americas (http://www.paho.org/hq/index.php?option=com_topics&view=article&id=427&Itemid=41484&lang=en).

Although strong epidemiological data suggest the association between Zika virus and the microcephaly epidemic, a causal link between the virus and the disease is still lacking and is limited to few case reports. Many questions still remain. Does the virus damage embryonic neural tissue? What is the percentage of fetuses getting infected when the mother acquires Zika virus during pregnancy? Does the stage of pregnancy interfere with virus ability to be transmitted to the fetus and the development of neurologic effects? Are there other neurological defects related to Zika virus infection? Is there another cofactor involved, such as malnutrition or other concurrent infection? All these questions are exceedingly important to provide counseling to pregnant women and those who are planning to become pregnant, especially in Northeastern Brazil. In fact, Brazilian authorities have been recommending avoiding pregnancy until this situation is further clarified.

The microcephaly epidemic impact is unimaginable. It is a tragedy. These children are compromised for life and the impact on their families is beyond any prediction.

Back to the story sent by Emma. A small town in the North of Pernambuco State, named Itapetim, has almost 14 thousand inhabitants and has reported 11 cases of microcephaly in the past 3 months. This very same town has been suffering from a prolonged drought, since September 2013 when the last reservoir went dry. Perhaps the storage of clean water or the limited resources has led to the best environment for arbovirus spread and the development of microcephaly.

But the Zika virus’s impact may be reaching further. An increase in Guillain-Barré syndrome cases has also been noticed in the Northeast of Brazil, possibly related to the epidemic.

Several groups have been trying to establish animal models to study the interaction of Zika virus with neural tissue. The forthcoming developments are critical to better understand the virus immunopathology and confirm (or refute) the association between the virus infection and neurologic damage in fetuses and in the infected host developing Guillain-Barré syndrome. Many things still shrouded in mystery.

Keep on the good work. I will keep on listening!

Esper

Earth’s virology course for 2016

Do you want to learn virology? Every spring I teach a virology course at Columbia University, and this year’s version has just started. I record every lecture and put the videos on YouTube. Here is a link to the playlist: Virology Lectures 2016. Lecture #1, What is a Virus, is embedded below as a teaser.

I strongly believe that the best approach to teaching introductory virology is by emphasizing shared principles. Studying the phases of the viral reproductive cycle, illustrated with a set of representative viruses, provides an overview of the steps required to maintain these infectious agents in nature. Such knowledge cannot be acquired by learning a collection of facts about individual viruses. Consequently, the major goal of my virology course is to define and illustrate the basic principles of animal virus biology.

You can find the complete course syllabus, pdf files of the slides, and reading at virology.ws/course.

My goal is to be Earth’s virology professor, and this is my virology course for the planet.

TWiV 373: The distinguished virology career of Julius S. Youngner

On episode #373 of the science show This Week in Virology, Vincent speaks with Julius about his long career in virology, including his crucial work as part of the team at the University of Pittsburgh that developed the Salk inactivated poliovirus vaccine.

You can find TWiV #373 at microbe.tv/twiv. Or you can watch the video below.



TWiV 372: Latent viral tendencies

TWiVOn episode #372 of the science show This Week in Virology, the TWiV-osphere introduces influenza D virus, virus-like particles encoded in the wasp genome which protect its eggs from caterpillar immunity, and a cytomegalovirus protein which counters a host restriction protein that prevents establishment of latency.

You can find TWiV #372 at microbe.tv/twiv

The switch from trivalent to bivalent oral poliovirus vaccine: Will it lead to polio?

bivalent OPVIn four months, 155 countries will together switch from using trivalent to bivalent oral poliovirus vaccine. Will this change lead to more cases of poliomyelitis?

There are three serotypes of poliovirus, each of which can cause paralytic poliomyelitis. The Sabin oral poliovirus vaccine (OPV), which has been used globally by WHO in the eradication effort, is a trivalent vaccine that contains all three serotypes.

In September 2015 WHO declared that wild poliovirus type 2 has been eradicated from the planet – no cases caused by this serotype had been detected since November 1999. However, in 2015, there were 9 cases of poliomyelitis caused by the type 2 vaccine. For these reasons WHO decided to remove the type 2 Sabin strain from OPV, and switch from trivalent to bivalent vaccine in April 2016.

After OPV is ingested, the viruses replicate in the intestinal tract, providing immunity to subsequent infection. During replication in the intestine, the vaccine viruses lose the mutations that prevent them from causing paralysis. Everyone who receives OPV sheds these revertant viruses in the feces. In rare cases (about one in 1.5 million) the revertant viruses cause poliomyelitis in the vaccine recipient (these cases are called VAPP for vaccine-associated paralytic poliomyelitis). Vaccine-derived polioviruses can also circulate in the human population, and in under-vaccinated populations, they can cause poliomyelitis.

There were 26 reported cases of poliomyelitis caused by the type 1 or type 2 vaccine viruses in 2015. Nine cases of type 2 vaccine-associated polio were detected in four countries: Pakistan, Guinea, Lao People’s Democratic Republic, and Myanmar. Removing the type 2 strain from OPV will eliminate vaccine-associated poliomyelitis in recipients caused by this serotype. When the US switched from OPV to the inactivated poliovaccine (IPV) in 2000, VAPP was eliminated.

The problem with the trivalent to bivalent switch is that vaccine-derived type 2 poliovirus is likely still circulating somewhere on Earth. The last two reported cases of type 2 vaccine-associated polio in 2015 were reported in Myanmar in October. The viruses isolated from these cases were genetically related to strains that had been circulating in the same village in April of the that year. In other words, type 2 vaccine-derived strains have been circulating for an extended period of time in Myanmar; they have been known to persist for years elsewhere. If these viruses continue to circulate past the time that immunization against type 2 virus stops, they could pose a threat to the growing numbers of infants and children who have not been immunized against this serotype.

Eventually as type 3, and then type 1 polioviruses are eradicated, it will also be necessary to stop immunizing with the respective Sabin vaccine strains. The switch from trivalent to bivalent vaccine in April 2016 is essentially an experiment to determine if it is possible to stop immunizing with OPV without placing newborns at risk from circulating vaccine-derived strains.

Over 18 years ago Alan Dove and I argued that the presence of circulating vaccine-derived polioviruses made stopping immunization with OPV a bad idea. We suggested instead a switch from OPV to IPV until circulating vaccine-derived viruses disappeared. At the time, WHO disagreeed, but now they recommend that all countries deliver at least one dose of IPV as part of their immunization program. Instead of simply removing the Sabin type 2 strain from the immunization programs of 155 countries, it should be replaced with the inactivated type 2 vaccine. This change would maintain immunity to this virus in children born after April 2016. Such a synchronized replacement is currently not in the WHO’s polio eradication plans. I hope that their strategy is the right one.