Becky Massaley (11 AM Micro) found our discussion about cancers caused by infectious agents (and therefore very potentially completely preventable by vaccination!) interesting. She found a recent report from the Morbidity Mortality Weekly Report on current epidemiology of HPV in the United States. Here is Becky’s summary:
Human papillomavirus (HPV) infection is the most common sexually transmitted disease (STD) in men and women in the United States. The viruses (HPVs) are prevalent and well-adjusted to their host. They are capable of insulating away from immune responses. HPV can be group according to the areas of the body where infection is found on external skin such as anal, genital area, and the oral mucosal. The mucus cutaneous HPV type can be further sub-divided into low risk (LR-HPV), mainly associated with benign warts. And high risk (HR-HPV) defined by their risk of progression or malignancy. The infections can cause abnormal tissue growth, and lesions, particularly in the immunocompromised person. Some HPV types only infect the genital area and may cause warts. Warts usually disappear spontaneously but occasionally may be resistant to treatment. Regrowth of lesions after treatment is frequently due to persistence of the virus in the skin surrounding the original wart. some may warts cause mild changes in cervical cells that do not turn into cancer, and some cause changes that may become cervical cancer or other types of cancer including penile cancer, anal and oropharyngeal (mouth and throat-cancers) if present for many years.
In adults, the disorder is considered a sexually transmitted infection, passed from person to person through intimate contact including vaginal sex, anal sex, and oral sex. The disease can also be transmitted vertically from mother to child, and during delivery. HPV infection is very common, although the majority of people have no symptoms (asymptomatic). Cervical cancer and other HPV related cancers are serious diseases that can be life threatening. The infection may cause the cells in the lining of the cervix, vulva and vagina, anus, penis, or throat to change from normal to precancerous lesions. If these lesions are not treated, they may turn cancerous. Among HPV related cancers, cervical cancer is the most common, with about 10,800 women getting cervical cancer each year in the US. Other cancers caused by HPV are less common, but oropharyngeal cancers (cancers of the throat, base of tongue and tonsils) are on the rise. According to the Centers for Disease Control, 8,400 people get oropharyngeal cancer each year. Some of these cases are related to tobacco or alcohol use, but it is thought that 72% of these cases are now HPV-related.
Recently, CDC conducted a studies which shows that about 14 million people are infected with HPV each year in United States. Another alarming concern is that the virus has about 150 types and 40 of these are transmitted sexually. I do learned from my microbiology class recently that proviruses are harmful and may remain later for a long period of time. Though they are latent, they are not safe for human body. Latent papillomaviruses are detectable only through the demonstration of HPV DNA in clinically and histologically normal skin and mucosa. Productive infections are associated with full viral gene expression and production of mature virus particles. While in persistent infection, normal cell function may dissolved and the events in the virus life cycle are disrupted. According to the study, the viruses that enter through the mucosa are considered high risk and may cause cancer. This includes genital skin, mouth, throat, mucus membrane, and also bodily fluids. Well I guess viruses are on the verge to take over human body and immune system. Base on the replication of the virus in its host, this might be a great concern for HPV epidemic and also pandemic (large geographical area or spread worldwide) in the future. CDC conducted a study which shows that the following cancers are related to human papilloma viruses, 66% of cervical cancers, 55% of vaginal cancers, 79% of anal cancers, and 62% of oropharyngeal cancers. The study also indicated that HPV vaccine (Gardasil) may prevent most cervical cancer in female, and anal cancer in both male and female if giving before expose to the virus. The vaccine may protects against 4 types of HPV (types 6, 11, 16, 18) that are linked to above condition. Although HPV is common among sexually active people, most are not infected with all four types that the vaccination may prevents. In clinical trials, individuals with current or past infections with one or more vaccine-related HPV types prior to vaccination were protected from disease caused by the remaining vaccine HPV types. The vaccine is expected to be long lasting.
|TABLE. Results of selected clinical trials* on human papillomavirus (HPV) vaccine efficacy against HPV vaccine-type precancers and anogenital warts — from the MMWR article|
|Cervical precancer||Bivalent and quadrivalent||Females||
Emily Zelger (11 AM Micro) saw the Salmonella outbreak from frozen dinners very alarming, and submitted this guest posting about another food-borne outbreak–this one right next door in Maryland. Listeria infections are actually pretty common, however as Emily notes in her summary below, the biggest concern is with pregnant women, as Listeria infections can lead to spontaneous miscarriage due to the ability of the organism to cross the placenta. It is essential that health care workers then be cognizant of the risks due to Listeria as part of pre-partum health care, and to warn expectant mothers to avoid infection. Here is Emily’s summary:
Seven people of Hispanic descent in the state of Maryland have been diagnosed with listeriosis, an infection caused by the Listeria monocytogenes bacteria. One person in California was also infected, but has since died from the infection. The outbreak had occurred from August to November of 2013.
The Maryland patients reported that they had all eaten a Hispanic-style soft cheese manufactured by Roos Foods in Delaware. In each of these cases, the patients bought the cheese from the same grocery store chain. A laboratory in Virginia collected samples of the cheese and confirmed the presence of Listeria monocytogenes in it. All consumers were warned by the Maryland Department of Health and Mental Hygiene not to eat any Roos Foods cheese products, in order to prevent a possible further spread of the outbreak.
Listeriosis is typically caused by eating contaminated food, such as the soft cheese mentioned above. Symptoms of listeriosis can include head ache, stiff neck, confusion, loss of balance, fever, muscle aches, and convulsions. If an infection is caused in a pregnant woman, it can lead to miscarriage, still birth, premature delivery or a serious infection to the newborn child. Five of the cases in Maryland were related to a pregnancy. Three of these include newborn children and the other two cases related to pregnancy were mothers of two of the children that had contracted the infection. Typically, infants, the elderly, and people with a weak immune system pose the greatest risk for developing listeriosis.
Listeriosis can be diagnosed by isolation from blood, spinal fluid, or amniotic fluid in a clinical laboratory on a selective media plate to determine the presence of L. monocytogenes in the body. If the diagnosis is confirmed, listeriosis can be treated with antibiotics such as ampicillin.
Listeria monocytogenes is a low G and C, Gram positive, bacillus shaped bacteria that is also a facultative anaerobe. It can survive in an environment with or without the presence of oxygen. L. monocytogenes can reproduce inside human body cells and destroy red blood cells. L. monocytogenes moves by way of peritrichous flagella at room temperature, but at human body temperature, the bacterium does not make any flagella. Because it doesn’t make any flagella at body temperature, the bacterium can move within host cells by way of actin rockets, produced by the polymerization of actin filaments. L. monocytogenes has thirteen serotypes that are capable of causing disease in humans, but 90% of diseases come from just three of the thirteen serotypes. The infection this bacterium causes is responsible for the most deaths among food related bacterial pathogens. Recent outbreaks of listeriosis due to Listeria monocytogenes have come from foods such as cabbage, cheese, and cantaloupes. These outbreaks often come from a single manufacturer.
It is possible to take a few precautions to prevent contracting listeriosis. All food should be washed and handled carefully, cooked thoroughly, and stored properly to ensure its safety. Choosing safer foods (pasteurized milk as opposed to raw milk or avoiding soft cheeses, for example) can also help prevent a listeriosis infection.
Via the Bad Ad Hoc Hypothesis competition, held at MIT last fall, a short video explaining a little bit about the range of Lyme Disease in the United States, and a surprising positive outcome from living in these areas:
I saw this news alert on Microbe World, which pointed to a primary research article in the American Society of Microbiology’s journal mBio. Honeybee colonies worldwide have undergone a phenomenon referred to as “colony collapse,” where the worker bees from a colony disappear. Pesticides, various viruses and bacteria, mites, and habitat loss have all been proposed as explanations however no clear front runner among these hypotheses has emerged. Honeybees are major pollinators of crops, with estimates that bees are responsible for pollinating up to $200 billion of crops each year. The number of beehives in the US has declined by 50% over the past 30 years, highlighting the seriousness of the problem.
The current study is a collaboration between researchers at the Chinese Institute of Agricultural Sciences, the US Dept. of Agriculture, the University of North Carolina, and Emory University in Atlanta, GA entitled “Systemic Spread and Propagation of a Plant-Pathogenic Virus in European Honeybees.” Viral infections do not easily jump between species. Indeed, although epidemiologists are extremely worried and closely track influenza viruses in mammal and avian populations, the so-called “bird flu” in itself does not readily infect humans. The concern about bird flu outbreaks is over a random mutation that allows a bird flu isolate to be easily spread between humans. Threats posed by viruses that infect a species extremely unrelated to humans are essentially non-existent, and so far there have only been rudimentary reports that this happens. This report from 2010 represents the first time that a plant virus had been implicated in human disease, however this study has not been followed up so far. The current study goes further, and clearly shows by a variety of methods that a plant virus can effectively replicate in insect cells, and infection of colonies with this virus is correlated with colony collapse disorder.
Most plant viruses are spread by herbivorous insect vectors that spread the virus from an infected plant to a healthy plant, and there is evidence that plant viruses can manipulate the behavior of insects that feed on infected plants. Tobacco Ringspot Virus (TRSV) infects a number of plants of economic importance, and causes malformation and stunted growth. A number of biting insect vectors have been implicated in the spread of TRSV, however additional spread via infected seeds is also critical in the long term spread of the virus. Honeybees have been found to play a role in this process by transferring infected pollen from plant to plant, however it had not been described previously that the bees could actually be infected with the virus by the pollen that they carried.
The researchers used bees from colonies kept at the USDA labs in Maryland, USA. Samples of workers from these colonies were analyzed for presence of the virus by several methods. Viruses were purified from whole bee homogenates, and visualized directly by electron microscopy–the picture above demonstrates the presence of virus particles that showed the same morphology as TRSV particles from plant sources. Several molecular analyses were also used, including polymerase chain reaction of isolated bee tissues using specific primer sets, and in situ hybridization of microscope slides of whole body sections of worker bees. Both of these approaches showed the presence of virus in a variety of tissues, indicating that the virus was actually replicating within the tissues of bees as opposed to being carried on the outside of the insect on pollen particles.
They further demonstrated the presence of TRSV in bees by analyzing the presence of virus in Varrao mites, which are obligate parasites of the honeybee and have been an important part of the problems facing the beekeeping industry. Indeed, it appears that the mites are able to transmit the virus between bees and are critical in the spread of the virus throughout a hive. The main block preventing easy infection of bees is the step of transfer and binding of virus to insect cells, and biting mites circumvent this process by introducing the virus directly into the body of the insect. The researchers found a strong correlation with the presence of TRSV in bee colonies plus other viral diseases of honeybees in colonies deemed “weak” or in danger of collapse. In contrast, “strong” colonies showed very low levels of TRSV and other seasonal viral infections of bees. They conclude by suggesting that the data argues that survival of honeybee colonies is dependent on infection with TRSV along with other specific viruses of bees.
This news alert has been popping up via several news sources over the past few days. I first saw it via the New York Times, however the video clip is a BBC news report detailing the regional response to this outbreak. Several islands in the eastern Caribbean Sea have been experience significant outbreaks of Chikingunya fever, a mosquito transmitted disease that fortunately has a relatively low mortality rate but a pretty high rate of infection. Indeed, the ease of infection in humans and the high level of debilitating symptoms of disease led several governments to consider Chikingunya virus in biowarfare programs before these were banned by international treaty. What makes this outbreak alarming is the rapid spread that the disease is making from island to island, and the fact that this is the first time that the virus has been seen outside of its endemic region in sub-Saharan Africa.
Chikungunya fever is caused by an RNA genome virus; the most closely related virus that might be familiar to BIO230 students is the Rubella, or German Measles virus, which is itself showing a resurgence in the US due to failure to vaccinate. Unlike rubella, Chikungunya virus is transmitted by the mosquito when it bites someone after having a blood meal on an infected individual. The incubation period is usually under a week, then the patient will exhibit a high grade fever, fatigue, and moderate to severe joint pain. The acute phase fever will generally resolve itself within a week or so, however in Chikungunya the joint pain will persist for weeks to months afterward. The initial symptoms of fever and pain lead many clinicians to initially diagnose Chikungunya fever as Dengue fever as the two diseases share a broad geographic region, however the prolonged joint pain is NOT characteristic of Dengue. This fact has led some epidemiologists to suspect that the incidence of Chikungunya fever is more significant that what has been reported.
There is currently no treatment for Chikungunya fever other than supportive therapies including rest, fluids, and non-aspirin pain relief. There is also not currently a vaccine for Chikungunya fever, although some clinical trials do show promise. Infection and recovery from Chikungunya fever confers life-long immunity to reinfection, so the current outbreak in the Caribbean does offer the opportunity to observe the spread and control of a highly infectious agent in an immunologically naive population. The initial outbreak was on the island of St. Martin in December 2013, with 3700 confirmed or suspected cases on St. Martin and several other eastern Caribbean islands. The Centers for Disease Control and Prevention have prepared a response document to the current outbreak. The spread of the disease into North America is unlikely, but not impossible. The virus is transmitted by two mosquito species, Aedes aegyptii and Aedes albopictus, both of which are found in the southern United States however mosquito control measures are effective at limiting the numbers of these insects. In order for an outbreak to occur, it is also necessary to have a reservoir of infected hosts for the mosquitoes to bite–the outbreak is dependent on having a population of infected individuals AND adult mosquitoes to maintain the outbreak. Consequently, in geographic areas where mosquito activity is seasonal, these outbreaks will stop as the mosquitoes are killed by cold weather. The main danger to US residents is with travel to Chikungunya outbreak regions, and the CDC recommends that all such travelers practice good insect avoidance measures.
It’s been a while since I have reviewed the various risks associated with eating, but I came across this Salmonella menace a few weeks ago. The Centers for Disease Control and Prevention published a case study describing a multistate outbreak of Salmonella enterica serotype Chester due to frozen meals. In November the CDC reported that 44 people became ill in 18 states during the late spring of 2010. Molecular analysis of patient isolates indicated sole source contamination and questionnaires completed by the patients suggested that “brand A cheesy chicken and rice frozen meals” were responsible. Of the 43 patients who were followed up, 16 of them required hospitalization however no deaths were reported. On the strength of the epidemiological analysis, the company recalled the product from the shelves and the outbreak strain was identified in 8 unopened containers. Investigation into the source during the manufacturing process did not turn up any production deficiencies or a conclusive common contaminated ingredient supplier. The best guess was that a single poultry supplier was the source in the outbreak. What made this case novel was that this episode represents the first time that Salmonella enterica serotype Chester had been reported in a widespread foodborne disease outbreak.
Editorial notes by the CDC point out that there is little in the way of negligence in either the supplier or production procedures used to bring this product to market. Simple Google image searching showed that the dinner in the above graphic was the one recalled in this outbreak. The label clearly says “Keep Frozen–Must be cooked thoroughly” and is considered a “not ready to eat” meal, as opposed to the hugely convenient “heat and serve” meal. Organisms such as Salmonella enterica and Shiga toxin-producing Escherichia coli are not effectively killed by incompletely reheating in the microwave, and require actual cooking in order to render them inert. The instruction to “allow dinner to sit in the microwave for 1 minute” is also a critical part of the cooking process, and is frequently ignored by consumers. The CDC notes that this outbreak highlights the need to educate the public on safe food handling procedures, and the need to follow the instructions prior to eating these products. Consumers also, if using a microwave oven to cook these products, need to know the specifications of their appliances and to ensure that their microwave ovens are able to be safely used to cook these.