Category Archives: Death from the skies
Here’s a special treat for all BIO230 students; due to a lapse in bonus submissions, I have at least temporarily regained control of the class blog. Alert BIO230 correspondent Heather G has requested an update on H7N9 influenza, a novel influenza isolate that epidemiologists worried, because of its lethality and its potential for further spread.
In late March 2013, the Chinese Centers for Disease Control reported laboratory confirmation of 3 cases of human infection due to an avian influenza, which was determined to be of the H7N9 variety, which had previously never been documented to cause infection in humans. The US Centers for Disease Control and Prevention published a summary of the outbreak this week in the Morbidity and Mortality Weekly Report. As of the end of April 2013, Chinese authorities had confirmed 126 cases of human infection in 8 eastern Chinese provinces, with a fatality rate of 19%. All cases to date appear to be sporadic and of environmental origin, as no obvious human to human contact has been demonstrated outside of 3 family clusters. The origin of the human cases remains under investigation, but is presumed to be due to exposure to live poultry such as chickens or ducks. Of the positive cases for which a complete patient history was available, approximately 75% of the patients has an underlying medical issue which may help to explain their susceptibility to the virus. The US CDC has requested domestic medical laboratories to be on increased surveillance to the disease, particularly with individuals who may have recently returned from this area of China.
Chinese laboratories have already sequenced the genome of this H7N9 isolate, and determined that all of the genes of the virus are of avian origin as opposed to being derived from genetic recombination between avian and mammalian viruses. The viral genome does contain several mutations which increase the ability of this virus to bind to and infect mammalian respiratory epithelial cells, and therefore contribute to the increased virulence of this isolate. Further analysis of this H7N9 variety indicate the presence of resistance genes to the adamantanes, which are a class of important antiviral medications. Consequently, this class of antiviral medications would not be indicated to treat this outbreak.
Chinese authorities are expanding surveillance into potential animal reservoirs with widespread laboratory screening in bird and mammal populations. So far 68,000 bird samples have been screened with 46 positive results. At the same time, 4500 swine samples were examined with no positive results. This suggests that within environmental reservoirs that the virus is being restricted to avian populations. The US government does not allow the importation of live birds, poultry, or eggs from regions with an active highly pathogenic outbreak, and are working to deploy screening procedures to assess whether wild bird populations might be able to import Eurasian influenzas into North American populations.
Editorial notes by the CDC report stress the worrisome nature of this outbreak, primarily because of the speed with which it arose, and because this is the first documented infection of an influenza variety previously believed to be restricted to birds. The CDC recommends that domestic clinical laboratories have plans in place to identify cases here should they arise, and to consider H7N9 infection in patients who have recently returned from areas where the outbreak is continuing. At present, authorities do not feel that travel to China should be restricted, however travelers should practice hand hygiene and safe food practices. Travelers should seek medical treatment for any upper respiratory-associated disease during or after return from travel.
Via Heather Griffiths (5 PM Micro) a timely alert: physicians in Sweden have published in the New England Journal of Medicine a case report detailing human infestation with Hypoderma tarandi larvae, most likely acquired from a reindeer reservoir. H. tarandi is a sub-Arctic insect that lays its eggs on the hair of reindeers. When the larvae hatch, they burrow into the skin and mature in a condition termed myiasis, and then leave the mammalian host via holes in the skin in the spring. Myiasis is a significant problem in many animals, and insects such as screwflies and botflies are frequently responsible. There are very few cases of human myiasis in the United States, and generally these occur with people who have traveled to tropical or sub-tropical locations and returned.
The current case report is a bit atypical, due to its geographic location. Among the 12 cases of human myiasis reported since 1980 in Norway and Sweden, patients typically presented with ophthalmomyiasis. For 5 patients between 2008 and 2010, all reported traveling to reindeer herding areas during the summer, when the insect agent was likely the most active. None of the patients recalled being attacked by a fly. Initial presentation of disease was via swollen facial lymph nodes and migrating swellings, and subsequently surgical removal of larvae from the eye was performed. Patients were treated with the anti-parasitic drug Ivermectin to kill residual larvae.
The recommendation of the doctors is that myiasis should be considered in people visiting reindeer herding areas, and that Ivermectin may have significant prophylactic potential in preventing surgery in advanced cases. I would further recommend spraying down all wrapped presents with insecticide as well, to further ensure your safety. On a final note, here is a repeat video of Hypnotoad, who we can all now diagnose with myiasis:
Entirely apropos of the upcoming class discussion on microbial control, I present this link to an excellent essay on Gizmodo, the Gadget Guide on how NASA worked to prevent a potential Earth-bound plague from pathogens that might have been introduced via returning astronauts. In the early days of the space program, the potential risk that returning astronauts might also bring back an infectious agent with them was not known. Consequently, NASA introduced pretty significant decontamination measures upon recovery of the astronauts.
With the Apollo missions, astronauts were put into a 3 week quarantine, which was expected to be a sufficiently long time period for any novel pathogens to incubate. The recovered equipment (spacecraft, cameras and film, moon rocks) were decontaminated with strong bleach and kept in quarantine as well. During quarantine, all generated waste as well as expunged air was incinerated before disposal.
Methods today are somewhat less stringent. NASA has created categories with specific associated risks, with Category I being for missions to the Sun, Moon, or other celestial body, with no interest in any potential biological system. Category V is for any mission that sets down on a foreign body and returns with materials to Earth. The risk factors (with the exception of Category V) are now not put in place to prevent the introduction of a pathogen into a terrestrial environment, but instead are designed to prevent introducing microorganisms from Earth into an extraterrestrial environment.
This is not as far fetched as it might initially seem. Tardigrades are microscopic animals that are able to survive the vacuum and cold of space just fine, however these organisms were put on board the International Space Station on purpose. Another story illustrates the potential dangers more clearly. Surveyor 3 landed on the Moon in 1967, and transmitted a number of pictures back to Earth prior to the manned Moon landings. Apollo 12 (the second manned Moon landing) was able to visit the Surveyor 3 landing site, and returned to Earth with the mounted camera, which now can be seen in the National Air and Space Museum.
Even though Surveyor 3 was constructed in a state of the art clean room prior to launch, biologists were able to recover viable Streptococcus cells that had been carried to the moon and back, and remained in a viable state for 3 years on the lunar surface, while being exposed to extremes of temperature, constant vacuum, and high levels of radiation. Because of this finding, current precautions include exposing the space craft to hydrogen peroxide vapors with multiple cycles of vacuum. Hopefully these precautions will prevent us from inadvertently destroying all life on another planet!
Via The Atlantic Monthly, a brief video about tardigrades, a class of microorganisms that are both undeniably cute and horrifying at the same time. Plus they can withstand incredibly cold and hot temperatures, as well as the vacuum of space.
If you’ve seen the news lately, you’ve probably seen that this summer marks the highest level of West Nile infections yet recorded. According to the Centers for Disease Control, just over 1100 cases have been recorded to date in 2012, and analysis of the surveillance tables indicates all of those cases have been reported since the beginning of June. The map to the right indicates where cases have been reported, with 75% of the cases coming from South Dakota, Texas, Louisiana, Mississippi, and Oklahoma.
West Nile is a mosquito transmitted disease that is also found in a number of animal reservoirs including many bird species. In fact, veterinary cases are an important datum that is monitored by the CDC to follow outbreaks of the disease. The spike in cases this summer is the result of higher levels of mosquito activity during the summer, although it is not clear at this time whether the increased numbers in humans is due to increases in the numbers of infected animals.
West Nile Virus is currently know to be transmitted to humans either by the bite of an infected mosquito, and a small number of cases have been demonstrated to be caused by blood transfusion. Consequently, screening of donor blood in done to prevent that route of infection. Most people who become infected with West Nile Virus (80%) show no symptoms at all, and become immune to further infection. The majority of the remaining people may develop mild disease 3 to 14 days following infection, with symptoms including fever, headache, and body ache. These symptoms generally resolve on their own with no intervention within a few days. Approximately 1 in 150 patients develop serious encephalitis, or infection of the brain, with symptoms ranging from high fever and stupor, to coma and death. Patients with serious disease may remain ill for several weeks, and there is currently no treatment beyond mitigation of the symptoms. Some neurological symptoms may be permanent.
Some news reports have conjectured on why this disease appears to be significantly more serious this summer than in past summers, and have raised the possibility of anthropomorphic climate change as being responsible, and the very mild winter, early spring, and hot initial summer months may have helped to stimulate mosquito breeding. This may be possible, but mosquitoes also require standing water for their reproductive cycle. The map at the left reports current drought conditions throughout the continental United States, and shows how much of the interior of the country is experiencing “extreme” drought conditions, and have been for several months now, which presumably would not be conducive for mosquito population growth. Interestingly, areas which have reported the highest levels of West Nile are highly correlated with areas of very low rainfall, which would seem to be counter intuitive. Mosquito control would certainly be an appropriate measure of restricting transmission. However if the frequency at which the mosquitoes are infected, due to a higher incidence in animal reservoirs, this could explain the increased transmission to humans even with a presumed decrease in the mosquito population due to low rainfall levels. The CDC collects data on mosquito and animal infection rates, but that data is currently under analysis for trends.