Man dies of Hantavirus infection in China conjuring memories of the deadly disease US had to deal with in 1993
Even as the world is grappling with the new coronavirus, another deadly virus has claimed the life of a man in China.
A passenger who died on a bus in China tested positive for this completely different virus — one more fatal that often produces similar symptoms, according to Chinese media.
"A person from Yunnan Province died while on his way back to Shandong Province for work on a chartered bus on Monday. He was tested positive for #hantavirus. Other 32 people on the bus were tested," Global Times, a Chinese daily, tweeted.
There was no immediate confirmation about the test results of the other passengers who were on the bus.
Hantavirus, however, is not new and the US had to grapple with an outbreak from a new type of the hantavirus way back in 1993.
According to the US Centers for Disease Control and Prevention (CDC), Hantavirus Pulmonary Syndrome (HPS) is a severe and sometimes fatal respiratory illness in humans caused by infection with hantaviruses. It is transmitted to humans by rodents such as mice and rats. Health experts say that HPS can be fatal and has a mortality rate of 38%.
There is no specific treatment, cure or vaccine for hantavirus infection. "However, we do know that if infected individuals are recognized early and receive medical care in an intensive care unit, they may do better. In intensive care, patients are intubated and given oxygen therapy to help them through the period of severe respiratory distress," says the CDC.
1993 US outbreak
In May 1993, an "outbreak of an unexplained pulmonary illness" occurred in southwestern US in an area shared by Arizona, New Mexico, Colorado and Utah known as "The Four Corners".
A young, physically fit Navajo man suffering from shortness of breath was rushed to a hospital in New Mexico and died very rapidly, describes the CDC.
Tests and investigations subsequently linked the pulmonary syndrome with a virus, in particular to a previously unknown type of hantavirus. In November 1993, the specific hantavirus that caused the Four Corners outbreak was isolated. The virus was considered so deadly that the US Army Medical Research Institute of Infectious Diseases (USAMRIID) was also roped in.
"The Special Pathogens Branch at CDC used tissue from a deer mouse that had been trapped near the New Mexico home of a person who had gotten the disease and grew the virus from it in the laboratory. Shortly afterward and independently, the US Army Medical Research Institute of Infectious Diseases (USAMRIID) also grew the virus, from a person in New Mexico who had gotten the disease as well as from a mouse trapped in California," says the CDC.
The new virus was called Muerto Canyon virus — later changed to Sin Nombre virus (SNV) — and the new disease caused by the virus was named Hantavirus Pulmonary Syndrome or HPS.
"The isolation of the virus in a matter of months was remarkable. This success was based on the close cooperation of all the agencies and individuals involved in investigating the outbreak, years of basic research on other hantaviruses that had been conducted at CDC and USAMRIID, and on the continuing development of modern molecular virologic tests. To put the rapid isolation of the Sin Nombre virus in perspective, it took several decades for the first hantavirus discovered, the Hantaan virus, to be isolated," says the CDC.
More cases discovered
While reviewing the case of the Navajo man, health experts discovered that the young man's fiancée had died a few days before after showing similar symptoms — a piece of information that proved key to discovering the disease.
The CDC says that Dr James Cheek of the Indian Health Service (IHS) back then said, "I think if it hadn't been for that initial pair of people that became sick within a week of each other, we never would have discovered the illness at all."
An investigation combing the entire Four Corners region was launched by the New Mexico Office of Medical Investigations (OMI) to find any other people who had a similar case history.
Within a few hours, Dr Bruce Tempest of IHS, working with OMI, identified five young, healthy people who had all died after acute respiratory failure. Multiple laboratory tests had failed to identify any of the deaths as caused by a known disease, such as the bubonic plague.
"At this point, the CDC Special Pathogens Branch was notified. CDC, the state health departments of New Mexico, Colorado, and Utah, the Indian Health Service, the Navajo Nation, and the University of New Mexico all joined together to confront the outbreak," say experts.
During the next few weeks, cases kept mounting in the Four Corners area. Virologists at CDC used several tests, including new methods, to pinpoint virus genes at the molecular level and were able to link the pulmonary syndrome with a virus, in particular, a previously unknown type of hantavirus.
Researchers knew that all other known hantaviruses were transmitted to people by rodents, such as mice and rats. Therefore, an important part of their mission was to trap as many different species of rodents living in the Four Corners region as possible to find the particular type of rodent that carried the virus.
Almost 1,700 rodents were trapped, and the culprit — deer mouse — was subsequently identified.
HPS not a new disease
As part of the effort to locate the source of the virus, researchers located and examined stored samples of lung tissue from people who had died of unexplained lung disease.
"Some of these samples showed evidence of the previous infection with Sin Nombre virus—indicating that the disease had existed before the “first” known outbreak—it simply had not been recognized," says the CDC.
Other early cases of HPS have been discovered by examining samples of tissue belonging to people who had died of unexplained adult respiratory distress syndrome. The researchers found that the earliest known case of HPS that has been confirmed has been the case of a 38-year-old Utah man in 1959.
According to experts, the sudden cluster of cases in the Four Corners area could be explained by the fact that during this period, there were suddenly many more mice than usual. "With so many mice, it was more likely that mice and humans would come into contact with one another, and thus more likely that the hantavirus carried by the mice would be transmitted to humans," say experts.
Is human-to-human transmission possible?
To date, no cases of hantavirus pulmonary syndrome have been reported in the US in which the virus was transmitted from one person to another
Researchers determined that, like other hantaviruses, the virus that causes hantavirus pulmonary syndrome, is not transmitted from person to person the way other infections, such as the common cold.
"The exception to this is an outbreak of HPS in Argentina in 1996. Evidence from this outbreak suggests that strains of hantaviruses in South America may be transmissible from person to person," says the CDC.
Several hantaviruses can cause hantavirus pulmonary syndrome
Since the outbreak in the US, experts have found that there is not just one hantavirus that causes HPS, but several.
"In June 1993, a Louisiana bridge inspector who had not traveled to the Four Corners area developed HPS. The patient's tissues were tested for the presence of antibodies to hantavirus. The results led to the discovery of another hantavirus, named Bayou virus, which was linked to a carrier, the rice rat (Oryzomys palustris)," says the CDC.
In another case in late 1993 — where a 33-year-old Florida man came down with HPS symptoms and later recovered — another hantavirus named the Black Creek Canal virus, and its carrier, the cotton rat (Sigmodon hispidus) were implicated. The person had not traveled to the Four Corners area.
"More recently, cases of HPS stemming from related hantaviruses have been documented in Argentina, Brazil, Canada, Chile, Paraguay, and Uruguay, making HPS a pan-hemispheric disease," says the CDC.
As of January 2017, 728 cases of hantavirus disease have been reported since surveillance in the US began in 1993. These are all laboratory-confirmed cases and include hantavirus pulmonary syndrome (HPS) and non-pulmonary hantavirus infection.