Global number of Measles cases rose by 20% in 2023.

The number of Measles cases recorded worldwide rose by 20% in 2023 (compared to 2022), with 10.3 million cases recorded globally, according so a joint press release issued by the World Health Organization and the U.S. Centers for Disease Control and Prevention. The main driver of this rise in cases is thought to be inadequate immunization coverage.

Two doses of Measles vaccine is sufficient to protect against infection with the disease, but 17% of children who should have received their first dose of the vaccine in 2023 are thought not to have done so (more than 22 million children), while 26% of children who should have received a second dose in 2023 did not do so. A vaccine coverage rate of 95% or higher for both vaccine doses is thought to be needed to prevent Measles spreading within a population.

Fifty seven countries are thought to have suffered Measles outbreaks due to gaps in vaccination coverage, a 60% rise on the 36 countries which suffered such outbreaks in 2022. The World Health Organization's African, Eastern Mediterranean, European, South-East Asia and Western Pacific regions were affected, with over half of outbreaks occurring in the African Region. Only the Americas Region was not affected by a Measles outbreak in 2023.

A doctor examines a girl with measles at the Republican Infectious Diseases Clinical Hospital, Bishkek city, Kyrgyzstan. Danil Usmanov/World Health Organization.

'Measles vaccine has saved more lives than any other vaccine in the past 50 years,' according to Tedros Adhanom Ghebreyesus, the Director General of the World Health Organization. 'To save even more lives and stop this deadly virus from harming the most vulnerable, we must invest in immunization for every person, no matter where they live.'

Measles is a human disease caused by a Virus in the Paramyxovirus family. The Virus infects the respiratory tract, then spreads throughout the body. It can lead to major epidemics with significant morbidity and mortality, especially among vulnerable people. Among young and malnourished children, pregnant women, and immunocompromised individuals, including those with HIV, cancer or treated with immunosuppressives.

Thin-section transmission electron micrograph revealing the ultrastructural appearance of a single Viron, of the Measles Virus. The measles Virus is a Paramyxovirus, of the genus Morbillivirus. It is 100-200 nm in diameter, with a core of single-stranded RNA, and is closely related to the Rinderpest and Canine Distemper Viruses. Two membrane envelope proteins are important in pathogenesis. They are the F (fusion) protein, which is responsible for fusion of virus and host cell membranes, viral penetration, and hemolysis, and the H (hemagglutinin) protein, which is responsible for adsorption of virus to cells. Centers for Disease Control and Prevention/Wikimedia Commons.

It is estimated that 107 500 people died of Measles in 2023, most of them children below the age of five. This is an eight 8% drop in fatalities compared to 2022. The reason for this lower fatality rate in 2023, despite a higher infection rate, is thought to be that more cases of Measles were reported in 2023 in countries with generally better healthcare and childhood nutrition rates, where infected children are less likely to die. However, this is not all good news, as even where Measles is not fatal, it can cause a number of severe health problems, including blindness, pneumonia, and encephalitis (swelling of the brain, often leading to brain damage).

Measles is one of twenty life-threatening diseases which it was hoped could be eliminated through vaccination campaigns by 2030 under the remit of the Immunization Agenda 2030 program. In the first week of November 2024, Brazil was declared to be Measles-free, meaning that the disease had been eliminated in the Americas Region, and at least one nation in each of the other regions, with the exception of Africa, also having Measles-free status. However, the decline in vaccine-uptake, and the subsequent rise in Measles cases around the world, means that this project is now threatened.

The African and Eastern Mediterranean regions are thought to be in particular need of urgent and targeted interventions to ensure vaccine availability and uptake, particularly in conflict-affected and other vulnerable settings. Greater surveillance for cases is also needed in all regions, in order to facilitate prompt responses to outbreaks when they occur.

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Chyliza colenutti: A new species of Chylizine Rust Fly from the Eocene of the Isle of Wight.

Rust Flies, Psilidae, are small-to-medium sized Dipteran ('True') Flies with elongate bodies and rounded heads, found largely in temperate regions of the Northern Hemisphere. Their larvae are parasitic on Plants, and some species, such as the Carrot Fly, Chamaepsila rosae, are considered to be significant agricultural pests. The Family Psilidae is divided into three subfamilies, the Chylizinae and Psilinae, which are considered to be sister groups, and the Belobackenbardiinae, which forms a sister to the other two groups combined. The oldest known fossil Rust Fly is Electrochyliza succini from Baltic Amber, which is probably Late Eocene in age. Electrochyliza succini is not placed within any extant subfamily, being considered to be a sister taxon to Chylizinae and Psilinae closer than Belobackenbardiinae, which suggests it appeared after the ancestor of these groups split from the Belobackenbardiinae, but before they had themselves diverged. 

In a paper published in the journal Insect Systematics and Diversity on 13 November 2024, Andrew Ross of the Department of Natural Sciences at National Museums Scotland, Jiale Zhou of the Key Laboratory of Zoological Systematics and Evolution at the Institute of Zoology of the Chinese Academy of Sciences and the Department of Entomology at the China Agricultural University, Christel Hoffeins of Hamburg in Germany, and Bill Crighton, also of the Department of Natural Sciences at National Museums Scotland, describe a new species of Chylizine Rust Fly from the Late Eocene Insect Limestone Bed of the Bembridge Marls of the Isle of Wight, England.

The Insect Limestone is a single bed of fine-grained micrite found within the Bembridge Marls member of the Bouldnor Formation on the Isle of Wight. This bed is noted for the production of exquisitely preserved Insects, which often show three-dimensional preservation, for which reason it is sometimes known as 'opaque amber'. This bed has been precisely dated to 34.3 million years before the present.

The new species is described upon the basis of a single specimen collected by George William Colenutt, a prominant Isle of Wight solicitor and amateur geologist, and donated to the Oxford University Museum of Natural History in 1931. The species is placed in the genus Chyliza, the sole genus in the subfamily Chylizinae, on the basis of comparison of its wing venation to that of living members of the genus, and named Chyliza colenutti in honour of the collector.

Chyliza colenutti, Holotype; (A) part, OUMNH M.177; (B) counterpart, OUMNH M.175; Insect Limestone, Bembridge Marls, north-west Isle of Wight, UK. Colenutt Collection. Scale bar is 5 mm. Ross et al. (2024).

The specimen is preserved in a split block as part and counterpart, and has a preserved body length of 3.9 mm and a maximum abdomen width of 1 mm. The forewing is 3.6 mm in length and 1.4 mm wide. All of the wings appear coloured towards their tips.

Prior to the description of Chyliza colenutti, the oldest described Chylizine Rust Fly was a Middle Miocene specimen identified as Chyliza sp. from the Middle Miocene Upper Freshwater Molasse of southwestern Germany, which is thought to be between 15 and 12 million years old. 

The dating of Baltic Amber can be problematic, as it ranges from Middle Eocene to Middle Oligocene in age (i.e. is between 48 and 27  million years old), and tends to reach collections via amber dealers, often trading hands several times before coming to the attention of a scientist, with any data on the location and age of the specimens often being lost. However, the majority of Baltic Amber comes from the Upper Blue Earth Member of the Prussian Formation, which has been dated to between 36.5 and 33.5 million years old. 

Electrochyliza succini in Baltic amber. Hoffeins Collection CCHH 1829-10. Scale bar is 1 mm. Ross et al. (2024).

This gives a gap of around 20 million years between Electrochyliza succini and Chyliza sp., which led many palaeoentomologists to conclude that there was a long gap between the divergence of the Belobackenbardiinae from the common ancestor of the Chylizinae and Psilinae, and the splitting of these two groups, particularly as no specimens assigned to either of these groups have been found in Insect-rich deposits such as the Dominican and Mexican ambers. However, if Ross et al.'s interpretation of Chyliza colenutti as a Chylizine is correct, then the group was present 34.2 million years ago, making it unlikely that it is more than two million years younger than Electrochyliza succini.

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Uranus approaches opposition.

The planet Neptune will reach opposition (i.e. be directly opposite the Sun seen from Earth) at 2.36 am GMT on Saturday 16 November 2024. This means that it will both be at its closest to the Earth this year, about 18.57 AU (18.91 times the average distance between the Earth and the Sun, or about 2 778 000 000 km), and completely illuminated by the Sun. While it is not visible to the naked eye observer, the planets have phases just like those of the Moon; being further from the Sun than the Earth, Neptune is 'full' when directly opposite the Sun. 

The orbits and positions of Earth, Uranus, and the planets of the Outer Solar System at 2.00 am GMT on Saturday 16 November 2024. JPL Small Body Database.

While the relative positions of the planets have no direct influence on life on Earth, the opposition of Saturn does present the best opportunity for observations of the planet by Earth-based observers. Uranus is never visible to the naked eye, but on Saturday 16 November the planet will be visible with a reasonable telescope in the constellation of Taurus, reaching its highest in the sky at about midnight.

Image of Uranus made with the Near-Infrared Camera on the James Webb Space Telescope, showing Uranus’s seasonal north polar cap and dim inner and outer rings, as well as  9 of the planet’s 27 moons – clockwise starting at 2 o’clock, they are: Rosalind, Puck, Belinda, Desdemona, Cressida, Bianca, Portia, Juliet, and Perdita. NASA/European Space Agency/Canadian Space Agency/Space Telescope Institute.

Uranus orbits the Sun at an average distance of 19.2 AU, completing one orbit around the Sun every 84 years. This means that the planet is almost stationary compared to the faster moving Earth, so that it reaches Solar Opposition only four days later each year than the year before, and reaches conjunction (when it is directly behind the Sun seen from the Earth), roughly six months later.

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Tubular fossils from the Terminal Ediacaran La Ciénega Formation of Sonora State, Mexico.

The first fossils of organisms with mineralized skeletons appear in strata from the Terminal Ediacaran, between about 550 and 538 million years ago. This appearance coincides with the decline of the organisms of the 'classical' Ediacaran White Sea Fauna. One of the most abundant of these early mineralized fossils is Cloudina, a diverse group of fossils with a cone-in-cone or funnel-in-funnel structure, although the extent to which Cloudina was mineralized appears to have been variable, with some forms heavily mineralized, some only lightly so, and others apparently having skeletons made from tough organic materials. Cloudina was first described from the Terminal Ediacaran Nama Formation of Namibia, but has since been found in Brazil, Spain, China, Oman, and the United States, and is considered to be a useful index-fossil for the Terminal Ediacaran. 

While Clodina is often the dominant fossil in Terminal Ediacaran assemblages, it is often found alongside a variety of other tubular fossils, such as Namacalathus, Namapoikia, and Sinotubulites. Sinotubulites fossils have a tube-in-tube structure and often have annular or longitudinal ridges, as well as both circular and polygonal cross-sections. Originally described from South China, Sinotubulites has also been described from Mexico, the United States, Brazil, Spain, and Namibia. Interestingly, which specimens of Cloudina have been discovered in many places with what-appear to be drill-holes, possibly the oldest known example of predation by boring, this has not been observed in specimens of Sinotubulites, even when the two are found together, potentially representing the oldest example of prey-selection.

Ediacaran fossils in the Terminal Ediacaran La Ciénega Formation of Sonora State, Mexico, were first described in the mid 1980s. The initial descriptions suggested a variety of tubular fossils were present, including Sinotubulites but not Cloudina. However, subsequent studies of the material led to the conclusion that these 'Sinotubulites' fossils were in fact specimens of Cloudina which had undergone taphonomic alteration, causing them to develop compactional folds which were mis-interpreted as the longitudinal striae of Sinotubulites.

In a paper published in the Journal of Paleontology on 10 October 2024, James Schiffbauer of the Department of Geological Sciences and X-ray Microanalysis Laboratory at University of Missouri, Clara Wong also of the Department of Geological Sciences at University of Missouri, and of the Department of Geosciences at Smith College, Cassidy Davis, also of the Department of Geological Sciences at University of Missouri, Tara Selly, again of the Department of Geological Sciences and X-ray Microanalysis Laboratory at University of Missouri, Lyle Nelson of the Department of Earth Sciences at Carleton University, and Sara Pruss, also of the Department of Geosciences at Smith College, re-examine the La Ciénega Formation fossil assemblage, using modern methodologies to provide new insights into the community structure preserved there.

The Caborca Block in Sonora comprises a series of Late Neoproterozoic and Early Palaeozoic strata laid down in shallow-marine environments on the edge of first a rift zone and then the southern margin of the continent of Laurentia. Here the early Ediacaran Period is represented by the Clemente Formation, which is followed by the Late Ediacaran La Ciénega Formation, and the Cambrian Cerro Rajón Formation. Uranium/lead analysis of zircons from the uppermost layer of the La Ciénega Formation places the age of this at 539.4 million years, the latest part of the Ediacaran. Zircon is a volcanic mineral that forms as liquid magma slowly cools to form solid rock. As zircon forms it can incorporate a variety of different elements into its crystal matrix, including uranium but not lead. This is useful as over time uranium decays to form lead, so any lead in a zircon mineral must be the result of the decay of uranium. Since the decay of uranium to lead occurs at a steady rate, it is possible to determine the age of zircons by measuring the ratio of uranium to lead within them.

Locality map and stratigraphy of the Cerro Clemente section: (1) Map indicating position of Caborca localities (yellow star) in northern Mexico, and plausibly correlative fossiliferous units (grey stars) in the southwestern USA. (2) Satellite image from Google Earth denoting the topography of the Cerro Clemente section with longitude and latitude markers. (3) Geologic map corresponding to the same map view in (2). (4) Photograph of collected coquina block. (5) Stratigraphic section with carbon isotope chemostratigraphy showing position of uranium-lead radiometric date (green star) and sampled fossil horizon (yellow star). Schiffbauer et al. (2024).

Schiffbauer et al. obtained a block from a silicified coquina bed within the La Ciénega Formation at the Cerro Clemente section measuring 15 cm x 10 cm x 10 cm. This was partitioned into a number of fragments, which were then treated to different analysis regimes, including dissolution with acetic acid to allow the collection of fossil residues, scanning electron microscope analysis, elemental analysis using an energy dispersive X-ray spectrometer, and thin sectioning for visual microscopy.

These methods enabled them to identify five distinct forms of tubes. Firstly, there were tube-in-tube structures with annular ridges and possible laminae, interpreted as Sinotubulites. Secondly, there were tubes made up of a series of tightly-fitting funnel-in-funnel structures lacking rims, interpreted as Cloudina. Thirdly, there were funnel-in-funnel structures with thickened and/or pronounced rims, interpreted as the Cloudinomorph Saarina. Fourthly, simple straight tubes, and fifthly, simple curved tubes.

Morphological groupings of fossils (SEM). (1, 2) Form 1, Sinotubulitids in lateral (1) and cross sectional (2) views: (1) lateral view showing diagnostic transverse corrugations; (2) cross section illustrating multiple tube-in-tube construction, with substantial silica overgrowth. (3), (4) Forms 2 and 3, Cloudinomorphs, Cloudina sp. indet. (3) and cf. Saarina sp. indet. (4): (3) Cloudina with two nested funnel units and no thickened apertural rims; (4) the other Cloudinomorph form showing thickened apertural rims with observable drooping imbrication. Also note slight change in growth direction or plastic deformation at tube midpoint, along with slight tubular compression. (5), (6) Forms 4 and 5, smooth tubes that are either straight (5) or sinuous (6). Scale bars are 1 mm (1), (3), (4), and (6), 500 μm (2), and (5).  Schiffbauer et al. (2024).

Of the identifiable individual specimens, 33 were tube-in-tube structures, 20 were non-rimmed funnel-in-funnel structures, 23 were rimmed funnel-in-funnel structures, five were straight smooth tubes, and ten were curved or sinuous tubes. Thus, Cloudinomorphs were the most abundant group, making up about 40% of the sample, with Sinotubulitids comprising about 31% of the sample, and unidentified tubes making up 28%.

The Cloudinomorphs ranged from 0.88 to 2.61 mm in diameter, with an average of 1.51. The rimless forms were on average slightly larger, ranging from 1.13 to 2.61 mm in diameter, with an average of 1.65 mm., while the rimmed forms ranged from 0.88 to 2.26 mm in diameter, with an average of 1.43 mm. The Sinotubulitids were generally larger than the Cloudinomorphs, ranging from 1.11 to 5.23 mm in diameter, with an average diameter of 2.41 mm. The indeterminate tubular fossils ranged from 0.36 to 1.84 mm in diameter, with an average of 1.21, and little difference between the two forms (the straight forms average 1.22 mm in diameter, the sinuous forms 1.17 mm). The length of the fossils was much harder to estimate, as fossils of this size are prone to fragmentation; the longest Cloudinomorph found was 4.49 mm long, the longest Sinotubulitid 5.82 mm, and the longest smooth tube 5.59 mm. 

Seen in thin section, much of the block was made up of densely packed tubular fossils. The majority of these were calcareous in nature, with only a minority of examples being silicified. However, the acid-extraction method produced only silicified specimens, with the calcarious fossils apparently lost from the portion of rock treated this way. This is likely to have given a distorted view of the nature of the total assemblage. Furthermore, the silicified fossils within the block cut into thin sections often had very fine skeletal walls, sometimes as little as 2–3 μm thick, while all of those extracted by acid etching were much courser, with the thinnest being 0.15–0.32 mm thick, suggesting that finer silicious fossils had also been lost. 

Petrographic thin section photomicrographs. (1) Silicified tube examples (brighter white material) in transverse section (left) and longitudinal section (right). (2) Silicified funnel-in-funnel tube in longitudinal section, non-orthogonal to the length of the tube. Note blocky calcareous infilling and potential fine layering in the tube wall. (3) Transverse plane of non-silicified tube, with apparent fine layering and blocky calcareous infill. (4) Longitudinal plane of non-silicified tubular fossil with fine layering and micritic infill. Scale bars are 1 mm. Schiffbauer et al. (2024).

The calcitic tubes visible in the thin sections appeared to be made from a fine micrite, with courser carbonate and even dolomite crystals separating them. This could also be seen in scanning electron microscopy images, where it could also be seen that while the fine structures of the fossils were preserved, they were altered by the development of courser crystals around them, with many Cloudinomorph fossils having an elliptical cross-section (interpreted as distortion of an original circular shape), whole Sinotubulitids showed flattening, irregular cross-sections, and corrugation. One smooth-walled tube appears to have been helically twisted along its length. This makes it unlikely that the original surface structure of any of the fossils was preserved.

Surface and deformative features of silicified fossils (scanning electron microscope images). (1) Sagittally flattened Sinotubulitid specimen. (2) Imbricated funnel rims (dashed white lines to guide orientation) of cf. Saarina specimen with little-to-no flattening. (3) Torted funnel (left dashed curve), broken funnel wall (arrow), and intact funnel aperture (right dashed curve) of Cloudina sp. indet. specimen. (4) Ovoid puncture (arrow) in smooth (curved) tube. (5) Subcircular puncture (arrow) in Cloudina sp. indet. funnel (infilled). Scale bars are 1 mm. Schiffbauer et al. (2024).

Backscattered electron imaging and energy-dispersive X-ray spectroscope mapping of the thin sections suggested that there were many 'ghost tubes' present, which could not be visually observed, which were very nearly identical in composition to the host rock. There were detectable primarily by a lack of iron, an element present in the dolomite matrix. 

Scanning electron microscope imaging and energy-dispersive X-ray spectroscope elemental maps of fossils in polished slab. (1) Overview giga-macro photomosaic of a portion of polished thick section; labelled rectangles correspond to scanning electron microscope imaging and energy-dispersive X-ray spectroscope elemental maps image regions as indicated. (2), (3) Silicified fossil in transverse section: (2) backscattered electron (z-contrast) image, with (3) corresponding overlain elemental maps for calcium, silicon, and iron. (4), (5) Calcareous fossil in transverse section: (4) Backscattered electron (z-contrast) image, with (5) corresponding overlain elemental mabs for calcium, silicon, and iron. Scale bars are 5 mm (1), and 500 μm (2), (5). Schiffbauer et al. (2024).

The La Ciénega fauna was first described in 1985 by palaeontologist Mark McMenamin of Mount Hollyoak College, who assigned the fossils to a group of morphotypes rather than trying to assign them to taxa, and believed the sediments to be Early Cambrian in age, at least in part because PreCambrian fossils were thought to be extremely rare (if accepted at all) at this time. Subsequently, some of the fossils were identified as Sinotubulites, an exclusively PreCambrian taxa (the Ediacaran Period had not been named as such at this time), although this led to the postulation that this taxon extended into the Cambrian, as this was the data assigned to the La Ciénega Formation. It was not until the recognition of Cloudina, also exclusively PreCambrian, and later an index fossil for the Terminal Ediacaran, that the La Ciénega Formation was recognised as PreCambrian in origin, with geochemical dating methods later confirming an End Ediacaran age.

Schiffbauer et al. interpret the La Ciénega fauna as a multi-taxa, Terminal Ediacaran assemblage, including Sinotubulites, Cloudina, and other Cloudinomorphs, probably Saarina or Conotubus, as well as other, unidentified tubular fossils. The preservation present is a mixture of silicification, which produces fossils recoverable by acid etching, and calcification, which does not. Many of the silicified fossils show plastic deformation, which is taken to indicate that they were not silicified in life, but rather as the result of some taphonomic process. Examined in thin section, the calcified specimens appear to show finer organic structures, supporting this hypothesis. This means that identification of the fossils from the silicified material only is unreliable. However, the preservation of what appear to be drill holes in some of these fossils, and the fact that these drill holes only appear to be present in examples of Cloudina and not Sinotubulites is likely to be significant, as this repeats a pattern seen in deposits of a similar age in Shaanxi Province, China, increasing the possibility that this represents some form of early predator-prey interaction, with predators able to select certain tubes as suitable targets for predation.

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Malaria in Ethiopia.

Between 1 January and 20 October 2024 more than 7.4 million cases of Malaria were reported in Ethiopia, with 1157 deaths recorded, a case fatality rate of 0.02%, according to a press release issued by the World Health Organization on 31 October 2024. On these infections, 95% were causes by Plasmodium falciparum. This is the highest number of cases reported in Ethiopia in seven years, and part of an ongoing rising trend of Plasmodium falciparum infections; in 2023, 4.21 million Malaria infections, with 527 deaths, with 70% caused by Plasmodium falciparum.

The overwhelming majority of cases occurred in the west of the country, with four regions accounting for 81% of all recorded infections and 89% of known deaths, with 44% of cases and 667 deaths in Oromo, 18% of cases and 56 deaths in Amhara, 12% of cases and 250 deaths in Southwest Ethiopia, and 7% of cases and 45 deaths in South Ethiopia. 

Geographical distribution of Malaria cases as of 20 October 2024. World Health Organization.

Of Ethiopia's 523 worodas (districts), 222 have been identified as having a high Malaria burden, together accounting for 75% of recorded Malaria cases in 2023. Fifty of these high-burden worodas are considered to be hard-to-access due to ongoing conflicts.

A slight majority of cases are males, who accounted for 56% of cases treated as outpatients and 52% of inpatient admissions. Children accounted for 16% of outpatients and 25% of inpatient admissions. This age and sex distribution is thought to be due to patterns of seasonal migration, with large numbers of adult male migrant workers seeking work in high-risk areas during the peak of the Malaria season. 

From 2000-onwards, Ethiopia had a steady reduction in the number of Malaria cases each year, driven by improved surveillance, roll-out of malaria interventions, and community health extension program. The number of cases fell to an all-time low in 2019, when only 900 000 cases were recorded, and there was no wide-ranging major epidemic, only sporadic local outbreaks. However, the country began to suffer a resurgence of the disease from 2021 onwards, with 1.3 million cases in 2021, 3.3 million cases in 2022, and 4.1 million cases in 2023. This return appears to have been driven by the Plasmodium falciparum strain of the disease, which caused 70% of the infections in 2023, and which appears to have become endemic in areas where it was not previously known.

Weekly trend of malaria cases in Ethiopia, 01 January 2021 to 13 October 2024. World Health Organization.

Malaria is caused by parasitic unicellular Eukaryotes of the genus Plasmodium, and affects a wide range of terrestrial Vertebrates. Five different species of Plasmodium can cause Malaria in Humans, with most infections caused by either Plasmodium falciparum or Plasmodium vivax, both of which are endemic to Ethiopia. The parasites are primarily spread via the bite of the female Anopheles Mosquitoes (males do not bite), but can also be spread through blood transfusions, organ transplants, or practices such as needle-sharing.

Photomicrograph of a blood smear containing a macro- and microgametocyte of the Plasmodium falciparum parasite. Both macro- and microgametocytes are products of the erythrocytic life cycle. Within a few minutes after the Anopheles sp. vector ingests the gametocytes, microgametocytes develop into microgametes, which are able to fertilize gametes. Centers for Disease Control and Prevention/Wikipedia Commons.

Malaria manifests with approximately 10-15 days after infection, as a fever, headache, and chills. Mild cases often pass soon, and can be difficult to identify as Malaria, however, more severe cases can be fatal in as little as 24 hours after the onset of symptoms. 

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