TThe threat to humans from bird flu appears to be increasing. As outbreaks of H5N1 – a dangerous strain of bird flu – continue to affect cows in the US, Canada, South America, Europe and Asia, the World Health Organization (WHO) reported on June 5, the first case of human infection with H5N2, a different strain of bird flu. The infection was fatal.
The case was first reported to the WHO on May 23 by health authorities in Mexico City, where a 59-year-old man with several other health problems was hospitalized. Before reporting shortness of breath, diarrhea and nausea, the man had been bedridden for three weeks. Tests performed by the national laboratory showed that the man had H5N2, and additional genetic sequencing confirmed the strain.
Unlike recent cases of H5N1 in people in the US, the patient had no known exposure to infected animals. (However, outbreaks of H5N2 in poultry have recently been reported in Mexico.) The good news is that none of the patient’s close contacts or those caring for him in the hospital have tested positive for the virus.
What does this mean for people
Bird flu generally does not cause serious illness in people, and in previous cases of rare human infections, the virus did not spread easily from person to person. The first report of human infection with H5N2 “doesn’t really change anything in my mind,” says Dr. Shira Doron, director of infection control at Tufts Medicine Health System. “We have seen sporadic bird flu infections in humans for a long time and it is very rarely transmitted to other humans. But like any bird flu, it’s worth watching to make sure it doesn’t herald a new phenomenon.”
Questions that need to be answered urgently
Genetic sequencing of the Mexican patient’s virus will be important, as it could reveal which animal it likely originated from or whether there are any worrying changes that signal that the virus is evolving to spread more easily between people.
Sequencing will also be key to potentially answering some questions about how the bird flu virus is spreading to more mammalian species. “There is probably a role here for different types of receptors in different species and in different tissues of those species,” says Doron, since the virus appears to preferentially infect the respiratory tissues of birds, the mammary tissues of cows, and the conjunctiva, or eyes. . , In people.
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“What is not clear is how the virus is introduced into any newly infected mammals and how it passes between them,” she says. “We still do not have a definitive understanding of how the virus is transmitted from cow to cow, because there are especially high concentrations in the mammary glands but not in the respiratory tract. It undermines our entire spectrum of understanding.”
The virus is approaching humans
The US Department of Agriculture reported that H5N1 was found in 11 house mice in New Mexico. Farms in the state have reported outbreaks of H5N1 in cows, so it is possible that the rats consumed unpasteurized milk from infected cows and became infected. But that means the virus is getting closer to people, as most people are more likely to encounter house mice than dairy cattle. “Any house, any home, any lodge or campsite can put humans in close contact with rats,” says Doron.
In the US, health authorities are monitoring H5N1 in wastewater, which could provide an early sign of rising cases. Scientists with WastewaterSCAN—a collaboration between academic researchers and the health data company Verily, which contributes data to the U.S. Centers for Disease Control and Prevention—retested old samples from municipal sewage treatment plants and found H5N1 in the samples about a week before there were reports of an unknown disease in cows in Texas, where some of the first outbreaks occurred. “If we had done real-time testing, it would definitely have provided an advantage [on the outbreak],” says Marlene Wolfe, co-director of the WastewaterSCAN program and assistant professor of environmental health at Emory University’s Rollins School of Public Health.
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The group continues to monitor H5N1 and will continue to do so in the fall and winter when other flu strains begin to spread among people. This way, we will be better able to determine whether bird flu is having any impact on humans.
Determining how much of a threat bird flu may pose to people is a growing priority for health officials, and learning more about how the virus is moving from species to species is critical to making that assessment. For example, it’s unclear which tissue samples from the mice were positive, so it’s not known whether the mice are transmitting the virus through their urine or feces (which could pose a risk to people who might come into contact with them). ) or through other means. Cows, on the other hand, don’t seem to excrete much virus in their urine or feces, so even though the virus is circulating in mammals, “it’s not necessarily highly transmissible,” says Doron. “We could get lucky here.”
However, some farmers have been slaughter of sick cows to avoid widespread cases and the potential for infected, unsalable milk. And “scientists should be concerned, as there is potentially always a first time that a genetic change could mean more transmissibility in humans,” says Doron.
A warning
The H5N1 outbreaks and the first human H5N2 case highlight the need for health authorities to rethink how they monitor the flu. “We didn’t realize that bird flu was circulating in cows for probably three months,” says Doron. “Similarly, there may be more H5N2 in Mexico, in more species than birds – and we need to do more surveillance. We need to broaden our minds in the future to look for the flu even in places where we think we won’t find it.”
This story originally appeared on Time.com read the full story
